IMCO -3 shorty

[fysis]

Anyone tried a 3 shorty on the 22 .Would it be hard to get up of the water ? The propshaft would still bee 5 inch under the keel.

[mrfixxall]

everyone seems to be running -2'',, a blackhawk is less then what yours would be,,i dont see a peoblem and you could always add a 1'' spacer if you did not like it.

[blackhawk]

Anyone tried a 3 shorty on the 22 .Would it be hard to get up of the water ? The propshaft would still bee 5 inch under the keel.

With Donzi's conservative X dimension a 3" is perfect IMO. But, going off memory, I THINK you have to do some mods to the upper to run a 3".

[fysis]

With Donzi's conservative X dimension a 3" is perfect IMO. But, going off memory, I THINK you have to do some mods to the upper to run a 3".
Hi Blackhawk. Yes the reason i asked was because i just put a 3 on .Did the cut out and welding like imco has on their upper.(spoke to Imco first about minimum clearence) They like to see 1/2 inch but a 1/4 work. Now i Have 3/4 clear with a 15.25 Prop.(Can send a photo of it if someone is intr.) So everything is fine the shaft is 5" under the keel wich is not extreme as you said more like average with shorties .My Donzis -98 had the shaft down 8 inch from factory. Just one problem The boat wont plane i was very confused about this .Tried different props but al loose grip at 10mph. Thought maybee the cone slipped in the upper and tried a LH prop and reversed it only 10 mph just the same. All test with 4 blades. Took the drive of yesterday and checked for signs of other problems since i cant imagine that the boat would bee impossible to plane with the shaft down 5 inch. Nothing is wrong. Dave at IMCO also thought the fenomen sounded strange with the prop at that level. But suggested to try a 5 blade. Confused is the word:confused: Theories or experience are welcome.

[CHACHI]

With a -2 you need an add on cavation plate. I would imagine a -3 would need one also.

Ken

[DONZI]

If you would add an extension box or sternjack, i think you would be pleasantly surprised with the combo.
I put an Alpha SS on a 22 and had the exact same condtion even with the 4 B. Then i added a sternjack and had the best of both worlds ,leverage and speed.Another member here is currently running my old set up on an 18C also and lovin it.

If you look at the combo of the fast 20 Cig.'s, it is pretty much Blackhawks & box.Mike Baldwins 20 Cig Imco and home made box is a great running combo also.


Here's an old ad from O.S.O. that would be worth contacting.
http://www.offshoreonly.com/forums/swap-shop/236650-bravo-stern-jack-sale.html

[LKSD]

The drive is probably just a little too high.. Try a 5 blade or try shimming down 1"... ;) Jamie / Lakeside

[roadtrip se]

Mr. X had the same experience. He abandoned the idea. Why space down, if a two inch will hit the sweet spot? As for the five blade, I am deep into them now. They are expensive and unless your set-up is really able to take adavantage of the performance capabilities of these props, this isn't a path I would take either, as it is a band-aid, not a solution, if you are utilizing them to overcome a set-up issue.

[blackhawk]

With a -2 you need an add on cavation plate. I would imagine a -3 would need one also.

Ken

X2, are you running the anti-ventilation plate? My boat's propshaft is 4.375" below the boat and I can get on plane with 3 blades. If I went any higher I would probably have to use a 4 blade. Granted it's not a 22C but I can't see how 5" is too shallow to get on plane. If the props you're trying have plugs for thru-prop exhaust make sure they are in. Also make sure your drive is trimming all the way down. You have trim tabs?

Is the prop blowing out just as the boat "rolls over"?

[fysis]

Blackhawk i agree with you. If at least a handful 22 running with -2 and seems to work great it should not bee impossible to get on plane one inch higher. The props i tested are without vent holes.(Bravo) And the drive in a most down position .Different hubs also. I tried to think of other possibilites like a slipping coupler but without sounds ,rubber smell or dust that seems pretty far away. I will try a 5 blade maximus before i do anything else but since i´m not even close with the 4 blade i doubt it. Of coarse i tested with the drive in al positions tabs down and so forth. The grip goes when it tries to go over the edge.or close. I send along a pic. over the cav plate as it looks. To bad we have the big shoot out here on saturday.:confused:

[fysis]

Here is the pic. of the cavplate

[blackhawk]

Blackhawk i agree with you. If at least a handful 22 running with -2 and seems to work great it should not bee impossible to get on plane one inch higher. The props i tested are without vent holes.(Bravo) And the drive in a most down position .Different hubs also. I tried to think of other possibilites like a slipping coupler but without sounds ,rubber smell or dust that seems pretty far away. I will try a 5 blade maximus before i do anything else but since i´m not even close with the 4 blade i doubt it. Of coarse i tested with the drive in al positions tabs down and so forth. The grip goes when it tries to go over the edge.or close. I send along a pic. over the cav plate as it looks. To bad we have the big shoot out here on saturday.:confused:

Check to make sure the drive is going all the way down(slightly negative) when trimmed all the way down. Going off memory the limit switch stops trim up and trim down so it may need to be adjusted. But I could be wrong as it's been a long time since I had a boat with limit switches. I agree 5" shouldn't be too high but I don't have first hand experience with a 3" shorty on a 22C. On other similar boats 5" is plenty deep. Other than that I am stumped.

[fysis]

Yes Its al the way down. The switch is only for not overtriming way up/out. My friend was just over with a maximus 30" i let you now tommorrow what happened. Very curious myself.Thank´s US Donzi riders for your help.

[fysis]

One more thing if i need a 1" spacer are there a special one just for the Bravo/Imco setup or will a Regular Bravo spacer (if there is such a thing) work. Thanks again .

[blackhawk]

Yes Its al the way down. The switch is only for not overtriming way up/out. My friend was just over with a maximus 30" i let you now tommorrow what happened. Very curious myself.Thank´s US Donzi riders for your help.

Then I'm stumped. IMO you should be able to get on plane with a 4 blade. Hell you should be able to get on plane with a 3 blade!

Keep us posted.

[fysis]

Okej tried the 30" Maximus today . First the same feeling as with the 4 blades but finally with a lot of slip i got the boat on plane. Had to keep the drive very close to most down pos. not to slip. could break it loose even at 40-50mph to much wind but did two runs ,hard to tell the slip at higher speed since i did not get very good RPM reading but GPS was 83.6 so something is wrong with the water going to feed the prop A Maximus 5 inch under the keel should plane at ease. Next step would bee try a std lower and take it from there. I don´t know if the nose kone could bee involved here?? Thank´s for your interrest. Anyone with similar experience?

[fysis]

Hi again . Today put on a standard Bravo lower had a Hydromotive nosecone. Back to 8 inch under keel with the propshaft. Tried a Mach Stern 30" 4 blade 89.75 mph @55-5600. Then tried the Maximus 30" that was the only one that could get me on plane with the -3 shorty. speed 86.25 mph no problem getting 55-5600 ?? guess the Maximus will bee kind of "heavy" 8 inch down. Tomorrow will try 32 Bravo and see what comes out. Then i have to get back to the Imco -3 and space it down. Another friend of mine just had similar problems with a -3 on his Arrow 830 even though he had an extension box. Anyone Now if the -3 is harder to get right then the -2 . I meen i´m still down 5 inches with it and cant get the boat on plane.???

[osur866]

personally I'd go back to the -3 and space down 1/2-1"

[fysis]

Yes that´s the next thing to do. First i will try the 32 Bravo today on the std. lower. Have you heard anyone succesfully using the -3 IMCO. A Pantera friend over here said he lost top speed over 3mph with the shape of the IMCO house compared to a standard lower at the same height . To put it short regardless of my cavitation problems. Are the IMCO design poor?? and is it just the actuall decrease in lengt that gives the higher speed for most users?? I´m not a convinced IMCO fan so far:garfield::garfield::garfield:

[osur866]

I've got a -2 on an 18 and it helped me gain 2-3 mph and my handling improved over the stock lower, I'm running 3 blade props and get on plane fine, there's a lil trick to the shorten lowers when getting on plane you kinda have to roll the boat up on plane, just takes a lil longer than the stock lower.

[RickSE]

I haven't seen anyone mention the use of tabs. Have you tried putting your tabs down to get on plane? Most of the bigger ZX's need tabs to get up on plane. They're a little different though since they suck air through the steps and blow out the props if you're too aggressive on the throttles.

[roadtrip se]

I have run a two inch shorty IMCO on my 22 since 2002. As I said earlier in this thread, I know a few people that have tried the three-incher, some that have some pretty deep knowledge of these boats, and none have had success with it.

The shorty is an awesome drive, in the right configuration. The more power you have, the more you will be able to take adavantage of the capabilities it can offer. Osur hit on it a little, but the end result is that it will allow you to turn wider diameter props with bigger pitches, and see some great handling improvements at all speed ranges. The advantages seem to show up most at 75 and up.

I suffer from no blow-outs in turns and the boat lands softly at high speeds. It does run flatter, so you have to prop test for bow lift. And as Osur said, you have to be more patient on the throttle rolling up on plane. The more blades you can turn, the better she will handle.

I run no tab any time.

Hope this helps.

[fysis]

Roadtrip. Thanks thats the best i heard on the subjekt so far. I was into that the case on the-3 where very different from the-2 . You think space it down one inch would be the thing do do and of coarse get the cavitation plate back in stock place again. So there has been guys trying them on 22:s before.interessting. One thing that seems mystery to me though is that for example my friend with a 20 foot stinger has a-2 Imco 3inch under the keel and no problems i don´t know anyone exept myself that cant plane it 5inch down. Ialso share your coment about tabs i use them only at our slow canal at about 10mph because it brings my deck down 2 feet for visibility. Tomorrow i have the 32 Bravo for test on my std lower then get back to the Imco. Thanks Roadtrip.:)

[roadtrip se]

Roadtrip. Thanks thats the best i heard on the subjekt so far. I was into that the case on the-3 where very different from the-2 . You think space it down one inch would be the thing do do and of coarse get the cavitation plate back in stock place again. So there has been guys trying them on 22:s before.interessting. One thing that seems mystery to me though is that for example my friend with a 20 foot stinger has a-2 Imco 3inch under the keel and no problems i don´t know anyone exept myself that cant plane it 5inch down. Ialso share your coment about tabs i use them only at our slow canal at about 10mph because it brings my deck down 2 feet for visibility. Tomorrow i have the 32 Bravo for test on my std lower then get back to the Imco. Thanks Roadtrip.:)
Yes, space the -3 down an inch and see how the handling goes for you, as you will be simulating what a -2 inch would probably do for your set-up. Should be interesting to see what the results are after you try it.
You mention the cav or splash plate in the "stock" position, too. This piece is critical to the performance and handling of the boat. I have spent a significant amount of time expirementing with this over the past couple of years, so I might have a tip or two for you here, if you like the way the -2 runs. Of course, as I already said, all of my experience is with the two incher, not the three, but don't give up the faith yet!
Good luck.

[fysis]

Roadtrip. Did a little testing with the Bravo32 on my std lower yesterday little more tests today seems hard to catch up more speed with the shaft 8 inch down.Got the rpm though. When i get back to the -3 and space it down 1" i will get some of the "wider section "of the case under the keel maybee 3/8 I mean the section where it bolts toghether with the upper. . Could bee disturbin?? Spoke to Dave at Imco and he said that the increase of distance from propp to cavplate under speed would not matter much. Seems your experience says that the distance are important even under speed , like the prop actually works against/with the plate even at speed is that right. Some speedmasters dont have any cavplate over the prop.Interessting subjekt. Really appreciate your Experience with the Imcos on Donzis and all the tips i can get. As you said ,loosing faith is close sometimes when there is no progress.:lookaroun:

[roadtrip se]

Dave at IMCO is a big help, but there is no replacement for real world testing.
My experience is that the distance from the prop to the splash plate is very important, not just at plane off, but in the way the boat handles at all speeds.
Want to do a little comparison, take a look at how Mercury attaches their splash plate to the Sportmaster. A bit different than the IMCO set up.

[fysis]

Roadtrip . I looked at the XR with Sportmaster and there is not much cavplate over the prop at al ,its further back. A photo of my situation is attached. As you see if i space down 1 inch a little of the wider section will be under keel .Maybee i could trim that of if it matters. You said you where more into 5 blades. Maybee i should try that later on but not just to get on plane . I still have a hard time looking att the photo and accept that the one inch would change the whole world. One thing the Classic transom is pretty straight upp compared to many others thereby putting the drive very close to it. That could possibly interfear since high propshafts work so good on other boats. My cavplate is very like the one on the photo earlier in the thread only little more sharp edges .

[blackhawk]

fysis, I'm as baffled as you are that you can't get on plane at 5". But there are some guys with good real world experience on here.

I do remember speaking to a guy several years ago with a Blackhawk 22C that swapped out his blackhawk drive for a bravo with a shorty and loved the boat. Going off memory the BH boats had a 2" higher X. So, combine that with a 2" shorty and the prop shaft is 4" higher.(unless I'm wrong on the X) Now, granted the hulls are slightly different but I would think the rocker in the BH hull would hinder it's planing ability, not help it. Just a thought.

No one is running a shorty or higher X that puts the prop shaft at 5" on a 22 on this board???

[fysis]

Well thank´s Roadtrip and Blackhawk for your interrest and tips. Otherwise it´s been pretty silent on this forum regarding the subject ,maybee people don´t want to just give out their on hard earned trial and error experiences and see me as a short cutter. Anyway broke the 90 mhp yesterday at 90.5 with the Bravo 32 on the standard lower .Will remove it today and wait for the 1" spacer to arrive. Best regards from Sweden. :sweden:

[Greg Guimond]

fysis August in the US is a tough month with many vacations. Also, while there may be a lot of members on here, very few of them are actually active. I'm sure you have done this but spend a lot of time searching different related terms and you may turn up some old threads that offer more help on your issue, which I know is frustrating. You can then PM folks and hope for the best. Good Luck :kingme:

[roadtrip se]

are obviously different on the 2" versus the 3". See below. This piece is what you get with the 1" and 2" plates, and it goes on top of the ridge on the upper. There is lots of opportunity for improvement with this set-up, as it is a mile away from the prop in its "stock" position. The Merc Sportmaster cav plate makes for a much more effective set-up, due to the tack-on splash plate proximity to the prop. All of this is out the window with the 3", because you are utilizing a different set-up completely, that can't really be manipulated. I stand by what I have said, I would sell the three inch and buy a two. They work and work well. If you decide to make the switch, I can help you with the results of a whole bunch of testing...

[osur866]

Just a thought here but are you running a cav plate with the -3? If your not then this could very much explain why while running a 5 blade your unable to get on plane, just thinking out loud here, like tripper showed above that plate is for the -2 and when you use a -3 that plate will not work account the clearence goes out the window. do you have a picture of the -3 bolted to the upper with the 5 blade just as you ran it?

Steve

[blackhawk]

. All of this is out the window with the 3", because you are utilizing a different set-up completely, that can't really be manipulated.

Ahhhhh, so the anti-ventilation plate is totally different on the 3" as compared to the 1" and 2"? If so that is interesting and may explain his problem as a prop should not ventilate at 5". Anyone have pics comparing the differences?

[osur866]

Ahhhhh, so the anti-ventilation plate is totally different on the 3" as compared to the 1" and 2"? If so that is interesting and may explain his problem as a prop should not ventilate at 5". Anyone have pics comparing the differences?

When using a -3" you need to use a different middle section of the upper otherwise any prop larger than about a 14" diameter will hit, look at the Imco website and check the upper on a -3 it has a lil S to it raising it up to give clearance.

Steve

[fysis]

:sweden:This is what it looked like with the 15 5/8 Maximus. (forget about the paint it´s al been removed). The cut out is very similar to the one IMCO uses. And Dave said that my version should work. Will send you a pic of the new cavplate i made that will go with the 1 inch spacer i´m putting on tomorrow.

[blackhawk]

fysis I was just reading on OSO that guys had to put on a anti-ventilation plate extension on their shorties to get on plane. According to the thread it can be hard to get on plane without it. Just a FYI.

[fysis]

Yes Blackhawk. I´m working on the problem and making progress. 92.47 mph with the old Mach Stern 30" Tach in bottom @ 6000 .That is with 1 " spacer on the-3. 19% slip at least. The "Old Mach" is to small will try other props this week. At least brooke the 80 knots barrier ( 80.4knots=92.47mph) The feeling with the shorty up there was positive. Keep you posted with the following.:):sweden:

[roadtrip se]

Blackhawk, I read the same posts you saw on OSO. The "anti-ventilation extension plate" that you are referencing is the IMCO "splash plate", what IMCO calls it, that I posted up at the top of this page, post #31.

The problem with this plate is that it mounts on top of the lip on the upper, which puts it miles away from the prop, and gives away too much prop slip because of it. Not to mention that the piece is not terribly durable and doesn't mount very well, to begin with. I have broken three of them over the years. I have posted a pic for reference. That would not be a terrible thing if it just broke the plate, but it normally takes a chunk of the upper with it. This has happened to me twice at about 1200 for the upper shell, plus labor to swap out and install gears. It ain't a pretty story to tell.

I have been conversing with Bjorn via email, and he is working on something better for the three incher, which you can see the beginnings of in his picture. Good stuff. I have designed a similar and better system for the two incher, with a lot of help from people like Phil and Charlie at Lip-Ship, as well as a good friend with some serious CNC and water-jet machine shop capabilties. Still messing around with it, but the results are great, and Bjorn is going down the right path, too.

[blackhawk]

Blackhawk, I read the same posts you saw on OSO. The "anti-ventilation extension plate" that you are referencing is the IMCO "splash plate", what IMCO calls it, that I posted up at the top of this page, post #31.
The problem with this plate is that it mounts on top of the lip on the upper, which puts it miles away from the prop, and gives away too much prop slip because of it. Not to mention that the piece is not terribly durable and doesn't mount very well, to begin with. I have broken three of them over the years. I have posted a pic for reference. That would not be a terrible thing if it just broke the plate, but it normally takes a chunk of the upper with it. This has happened to me twice at about 1200 for the upper shell, plus labor to swap out and install gears. It ain't a pretty story to tell.
I have been conversing with Bjorn via email, and he is working on something better for the three incher, which you can see the beginnings of in his picture. Good stuff. I have designed a similar and better system for the two incher, with a lot of help from people like Phil and Charlie at Lip-Ship, as well as a good friend with some serious CNC and water-jet machine shop capabilties. Still messing around with it, but the results are great, and Bjorn is going down the right path, too.

Ah, so that pic you posted earlier was their "splash plate" and can be used on a 1", 2" AND 3" shorty? I thought you were posting it because it was used on the 1" and 2" but not the 3". And according to the thread on OSO they said to make sure and use it with the 3", so I am a little confused. Is this what they use to keep the prop from ventilating, or is it an "add-on" above and beyond what they use for a plate?

Unfortunately I know very little about shorties so I can't offer much help. But I would like to see fysis get this figured out. And IMO his ventilation issues are directly related to the anti-ventilation plate as a 5" prop shaft depth is still a little conservative.

EDIT: Okay in looking and reading post #35 again it looks like those pics are with the 3" shorty and the mods you did to the upper for prop clearance and had a anti-ventilation plate made/added?

And I know most people call them a cavitation plate but it drives me nuts! LOL

[axelkloehn]

Yes Blackhawk. I´m working on the problem and making progress. 92.47 mph with the old Mach Stern 30" Tach in bottom @ 6000 .That is with 1 " spacer on the-3. 19% slip at least. The "Old Mach" is to small will try other props this week. At least brooke the 80 knots barrier ( 80.4knots=92.47mph) The feeling with the shorty up there was positive. Keep you posted with the following.:):sweden:

am I looking right and I see a rear-spoiler??? :shocking:

[Just Say N20]

I have never seen a classic with the grab rail running bow to stern, or with one crossing the entire stern. I kinda like the long side rails.

92+ mph and the stock trim tabs are still in place. Amazing.

[roadtrip se]

I have never seen a classic with the grab rail running bow to stern, or with one crossing the entire stern. I kinda like the long side rails.
92+ mph and the stock trim tabs are still in place. Amazing.

Bjorn has shared a few shots of his boat with me in the past and recently. I like it. We all have a different way of making these things are own. I see it every time at a gathering. Pretty cool.

As for tabs, did you happen to notice my transom, Bill? I know it is a sore subject around here, and I will openly aknowledge how useless Bennetts are in a performance application(slow, flimsy, slow), but if you don't use them, then why bother messing with them. BTW, to throw more gas on the tab fire,
I just received notice of another local handling opportunity being tamed dramatically last night by addressing the rigging issues and set-up, not hitting a switch. The boat is a 2005. He is still running a little tab at a hair above neutral, but nothing like before....It ain't easy, but it can be done.

Now back to cavitation plates, splash plates, extensions, or whatever we are calling them now....

[osur866]

Stock single ram Bennetts on my 18, anything above 55 their high and dry.

[fysis]

I have never seen a classic with the grab rail running bow to stern, or with one crossing the entire stern. I kinda like the long side rails.

92+ mph and the stock trim tabs are still in place. Amazing. Hi there N20. I made the grabrails myself because i like the look of them and also beeing very practicle to keep myself from falling off late fridays and saturdays:party: :wink: and when you want to get a hold o the boat you got something to grab. As far as trimtabs goes I made them 4 inch longer using an alum plate bolted with countersunk bolts from the downside.BUT only uses them in a 12mph canal to keep the bow down for visibility(difference 1.5 feet) since i bolted the seats directly to the floor in a laid back position i sit low.(and very comfortable) 2 reasons for that. That way the windshield works as one ,I still be able to here engine not just the wind.(no googles)Also with the seats very rigid bolted to the floor i get a better sence of the boat. Playing with tabs at 90+ i would not even think of.But RT you where on something there I havent tried so far but have thought of ,like have the tabs in a "locked assisting position" to lengten the boat but then again would take a summer to find the spot and the risk of just getting more wet surface slower you down.:sweden:

[fysis]

Anyone having some experience /or comparrison to chare about Hydromotive Q4 or Q4X compared to Bravo on the 22C:sweden: