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View Full Version : 22' classic w/blackhawk dr.



bcamplin
07-28-2006, 12:12 PM
I have a 1996 30th anniversary 22' classic with a blackhawk drive. The boat has a terrible tendency to porpoise. I have to keep tabs down at all times to prevent this whisch of course limits my speed. Any help with this would be appreciated.

Thank You

RedDog
07-28-2006, 12:19 PM
A question will need to be answered first:

Is it a Blackhawk hull? Meaning the hull has rocker built it to it and has the x-dimension been raised over a standard 22?

An easy way to see if the x-diension is higher is to look at your exhaust tips. Are the tips so high on the transon that a portion of the top of the exhaust flange has been cut off?

What type of trim tabs do you have - Bennetts or K-planes?

bcamplin
07-28-2006, 12:29 PM
A question will need to be answered first:
Is it a Blackhawk hull? Meaning the hull has rocker built it to it and has the x-dimension been raised over a standard 22?
An easy way to see if the x-diension is higher is to look at your exhaust tips. Are the tips so high on the transon that a portion of the top of the exhaust flange has been cut off?
What type of trim tabs do you have - Bennetts or K-planes?

Hi Red Dod the boat has k-planes and the exhaust tips have not been cut. Do not quite understand what you mean bt hull rocker.

RedDog
07-28-2006, 01:26 PM
Think of the shape of the "rocker" on a rocking chair. Donzi added "rocker" to the transom end of the 22 Classic hull for the "true" or "original" Blackhawk Donzis. The rocker is needed to create bow-lift that the Blackhawk drive does not give you like a standard Bravo drive - its a leverage thing. The Bravo drive sits deeper in the water.

So, if you don't have a Blackhawk hull - you have a 22 Classic with a Blackhawk drive - that could explain your problem.

Or maybe you just need more drive time experience. Start with your tabs down and as you gain some speed raise them slowly as speed increase.

glashole
07-28-2006, 02:53 PM
if you check the manufacturer's plate by the drivers seat it will say blackhawk in the model #

if it is a blackhawk you have to drive it with the tabs anyways

just type blackhawk into the search section of this site and spend the next few hours reading

good luck


Shea

Injun Joe
07-28-2006, 02:57 PM
BC...

I had a tough time with my BH porpoising like crazy in the 30-40 mph range at first. More set time will help. I am still learning how to drive this thing - it is tricky - with varying fuel loads, wind, wakes etc. I always start out with the tabs full down and bring them up gradually... It seems like unless we are really flying, the tabs are in the water a bit.

You can see the exhaust Red Dog was talking about in the attached photo. Also, if you have a rockered BH hull the fuel tank is further back... under the storage locker in the cocpit floor.

Good Luck,
-CH

Lenny
07-28-2006, 03:18 PM
NOT to hijack this, but does this hold true for (1987) 18s as well? My tips are cut flat at the top and tight up against the Joint area. Are all 18s like this? I had clearance issues after a few upgrades. Perhaps this explains part of it. Or, is that just how 18s are?

NO, you either have a raised X dimension or some aftermarket exhaust that has created clearance issues.

On stock 18's the tips are not cut-off at the top of the ring and do not extend into the joint part of the hull as Blackhawk drives do on Blackhawk hulls. On the Blackhawk drive and Blackhawk hull they have to cut the top 1/4 off the large flange on the exhaust so as to NOT extend into the joint. Blackhawk boats have the same "measured" X-dimension as the 22 Classics when measured (located) from the hull bottom, BUT, the Blackhawk is missing 2" from the hull bottom when compared to a Classic 22, hence the motor sits higher between the stringers, and thus closer to the deck.

tmdog
07-28-2006, 06:12 PM
[QUOTE=Lenny]NO, you either have a raised X dimension or some aftermarket exhaust that has created clearance issues.
On stock 18's the tips are not cut-off at the top of the ring

Beg to differ. My 1988 18C came with the cut ring. I do have clearance problems when modified with after market exhaust and filter. Hence the hatch scoop I installed. When I purchased 10 yrs. ago it was equipped with the factory exhaust. Unless I have a bastard.

goatee
07-28-2006, 10:57 PM
funny thing is,,, noone has even mentioned the prop.:propeller
what prop are you spinning?

Lenny
07-28-2006, 11:50 PM
[QUOTE=Lenny]NO, you either have a raised X dimension or some aftermarket exhaust that has created clearance issues.
On stock 18's the tips are not cut-off at the top of the ring
Beg to differ. My 1988 18C came with the cut ring. I do have clearance problems when modified with after market exhaust and filter. Hence the hatch scoop I installed. When I purchased 10 yrs. ago it was equipped with the factory exhaust. Unless I have a bastard.

TMDog, I mean stock, factory exhaust, I'd be VERY surprised to see this cut flange area on a stock 18 and X dimension with factory exhaust. Definately with aftermarket exhaust stuff. The BH 22 is the only "stock" DONZI I am aware of that has had this go out the door with this modification configuration.

tmdog
07-29-2006, 07:45 AM
[QUOTE=tmdog]
TMDog, I mean stock, factory exhaust, I'd be VERY surprised to see this cut flange area on a stock 18 and X dimension with factory exhaust. Definately with aftermarket exhaust stuff. The BH 22 is the only "stock" DONZI I am aware of that has had this go out the door with this modification configuration.


Lenny, Clarify. Everything was stock on the 88 18C. Stock exhaust and a very tired Merc. 350. the flange was cut. When disassembling, all parts seemed like factory and never was taken apart previouly. From a keen observation point, all mechanicals looked very original except for the wiring which was done half arse. Wish smeone would shed some light on this subject. My flange looks the same as posted by Coldwater.

DonCig
07-29-2006, 08:29 AM
The very first thing to remember is that not all exhaust tip flanges are the same diameter!

My stock exhaust tip flanges were not cut but went all the way up to the rub rail (Corsa tips 1997 Stock 18').
Now my new Stainless Marine flanges are cut to clear the rubrail.

The exhaust tip location is only a guideline as to the presence of a higher X dimension. If you want to know for sure, you are going to have to measure the boat.

I might suggest that you measure the centerline of the propshaft in relation to the bottom of the keel. The water going past the lower drive unit does not know where your X dimension is, but it knows how much surface area of drag it has to go by, so take the following measurement and compare it to other like models.
Blackhawk drives on different brands of boats that I have measured have had their propshaft centerlines measured at .5" above the bottom of the keel to 5.5" above the bottom of the keel or pad.
I would expect most older vintage Bravo, Volvo, Cobra and Alpha drives to have the stock propshaft centerline approximately 6" to 8" below the keel. My Donzi Classic 18 1997 had the propshaft 7" below when stock, when I added a -2" Imco shorty, the propshaft centerline was moved to 5" below the keel, and now with the Blackhawk it sits 1" higher than the keel. The Blackhawk drive is 8" shorter than a stock Bravo drive. So as you can see, this is not rocket science.

Good Luck, Don

Don

BigGrizzly
07-29-2006, 09:54 AM
Now to answer the question that was asked! It sounds like you have a 1996 classic with the rocker hull and a blackhawk drive. It is only a black edition if it has the graffics. there were only 40 produced. However several were produced without the graffics and gold brightwork. these are identicak in all other respecs. The biggest problem is they porpose terribly and there is no way to stop it except with the tabs. They will be going along fine WFO then for no apperent reason it starts. Three bounces at WFO and it stands on its tail. There have3 been many posts on this subject. Yes it needs tabs!!! Now back to putting Electric power assist hydraulic steering on my Corsican, and boy is it neet, no belts or brackets on the engine. More on this project later!

fegettes
07-29-2006, 10:42 AM
Does anyone have any input on replacing the stock tabs with longer, maybe the 24" tabs, to stop, or reduce, the porposing?

bcamplin
08-01-2006, 12:05 PM
Think of the shape of the "rocker" on a rocking chair. Donzi added "rocker" to the transom end of the 22 Classic hull for the "true" or "original" Blackhawk Donzis. The rocker is needed to create bow-lift that the Blackhawk drive does not give you like a standard Bravo drive - its a leverage thing. The Bravo drive sits deeper in the water.
So, if you don't have a Blackhawk hull - you have a 22 Classic with a Blackhawk drive - that could explain your problem.
Or maybe you just need more drive time experience. Start with your tabs down and as you gain some speed raise them slowly as speed increase.

hi red dog. I do have a rockewr type hull, also checked the transom and the bezels around the exhaust have been cut off at the top. Any help is appreciated.
Bill

Pismo
08-01-2006, 12:12 PM
Lots of stock non-blackhawk 22s and 18s have exhaust tips with the top of the flange cut off (like mine). They must have had some leftovers that they used on hulls others than blackhawks. Picture here. They are far from the rubrail in a stock setup.


http://www.donzi.net/forums/showthread.php?t=38796

glashole
08-01-2006, 12:55 PM
I replaced the 150 K-planes on my blackhawk with the larger 280's and they are alot more responsive now

you can sometimes find a good used set if you are willing to wait

regards

Shea

blackhawk
08-02-2006, 08:59 AM
I replaced the 150 K-planes on my blackhawk with the larger 280's and they are alot more responsive now
you can sometimes find a good used set if you are willing to wait
regards
Shea

Yep the 150s are worthless. I replaced mine with the 280s as well and it really helped the boat stay more level in the slop. I think I just saws a used set of plates for sale on OSO.