What kind of speed in a 18 with 350hp

[tommymonza]

Could some of you give me an idea what speeds everybody is achieving with a mild 325-350hp motor.

[BigGrizzly]

It all depends on prop, out drive and the real horse power the engine has, usually high 50 to low 60 mph

[Lenny]

Could some of you give me an idea what speeds everybody is achieving with a mild 325-350hp motor.

I think 325-350 at the prop should yield you high, high 70's WITH the right drive and prop. (2" shortie etc)

[BigGrizzly]

Lenny, talk to the Scorpion guys with the shortys high 70 is not going to happen with that HP.

[tommymonza]

1.5 to 1 outdrive with a stock X dimension.

What is your guys experience with going to a 1.73 or 1.82 ratio and swinging bigger props? Any gain over the common 1.5 ratio.?

[smokediver]

300 horsepower gets me 65 . some see close to 70 . i wouldnt change a gear ratio for what you are talking about . i have a 1.62 ratio . the 1.5 or 1.47 i think is better as it is a little stronger gear set .

[BigGrizzly]

Do not wast your time on changing ratios. It works on high HP motors but yours is not in that category. It would be a waste of time and money and results would be disappointing. I am just telling it like it is.:garfield: A good 383 Cid will go in low to upper 70s depending on ponies, and 350 hp is not enough.

[The Hedgehog]

It all depends on prop, out drive and the real horse power the engine has, usually high 50 to low 60 mph


A 377 CID mag will get 71-72 on the perfect day per Steven Whitney. He went to a shorty. Now I think he hits 73 ANY day (Steve, where are you?)

I have a 383 mag with 350 hp and I get that same speed with a 1.5 and a Turbo 23. At the high 50's you can hit the gas and pull HARD to the high 60's. Just ask DonziVol who was in my boat on Sat.

[The Hedgehog]

Lenny, talk to the Scorpion guys with the shortys high 70 is not going to happen with that HP.

I thought that they got 75 with the scorp on a good day. Maybe that is with a shorty too.

[tommymonza]

Thanks guys for the info .

Kinda doubting these speed claims over here on this thread and just checking with the little boat pro's to see if i am correct.

http://www.offshoreonly.com/forums/prop-talk/210936-am-i-crazy-does-seem-right.html

[BigGrizzly]

OH really, Thats is why we are here. I think most of these guys have genes from the Bass Boat crowd.:eek: Just listen to us and be realistic. Be careful of our sarcasm sometimes we get that way, no harm no foul. What you will find is that most of us have made the mistakes and paid the price. Now when it comes to Smoke Diver, His 300 ponies is on steroids and he has paid the price for mistakes, and he listened to us. Imagine if he had not. Just take it slow.

[mrfixxall]

DC18 has a 2008 c18 with a 350 mag(330hp) with a clever from DAH propeller and is running 67.somthing..

[tommymonza]

I meant you Donzi pro's. I know there is a wealth of expermentation and knowledge in the smaller deep v class over here than anywhere else.

What is the speed gain with a raised conservative X dimension.I am getting ready to do something with restoring my boat and would like to know if is worth it to raise the dimension. My boat carries the bow quite well and has just a tad more rocker in it than an 18 Donzi.I would like to raise itenough but not so far as to deal with full blown cavitation all the time .A little positve trim would be nice to still keep also.


Plus this little ciggie looks like a blast.80 mph at 5200 out of a 700hp big block.http://www.vimeo.com/4374769

[BigGrizzly]

Your treading on really thin ice here. There are mixed reviews on this area. It has been said 10 mph with higher X, but that is on really faster boats 80 and higher. It is kind of like nose cones. Now a bravo drive with the same prop height as an SS is slower then an SS. Then there is handling. Here comes the can of worms. Everybody has theories and what ifs. Few have ever done it with NO other changes. That6 being said there is the flaw in data.

[tommymonza]

My current engine is a 355 that i had Roger Munn build me years ago with some head work a lively cam and CMI Elbow tubes .Maybe a 325 hp motor i can't imagine much more out of it. I have yet to do anything with an intake and carb . Any suggestions? I currently have on the motor a Quadra jet off a stock 330hp 454 Mercruiser. I like the small bore primaries on them and figured the jetting was close for now. Did not want to run it lean.

Drive is a 1.5 to 1. I get a little porpoising at wide open if i positve trim a little to much over nuetral with a cleaver not sure what size right now.. So i feel i have plenty of bow lift from the hull itself.

I know this is the Donzi talk forum but i will show you a pic just to illustrate the running attitude of the boat at speed with a shade over nuetral trim.

My old Baron that i sold to my buddy he put the asd6 Arneson on it and it rides like it is on rails when you are jumping waves at speed .but he said it rides so flat in the calm that it took all the fun out of the boat.

[Lenny]

Although I DO agree with you Grizz I can say that my 2 3/4" raised X dimension, 8" setback, Alpha 1:5, Cleaver boat (18) runs 71 GPS at 5100 rpm with a 400 hour 1987 350 MAG carbed motor. ( Verified via GPS more than once. :yes: I have not had it out yet this year with its' "changes" yet to see where it ends up now.

This boat in no way had 300 HP available.

Jeremys' Scorpion 18 runs, to date, 77.3 GPS mph with the 2" shortie Bravo, 1/3 of a tank of fuel, 1' of chop, 1 person in the boat and a labbed 27" Mirage+. FACT

[tommymonza]

Lenny did you run your boat at all with the raised dimension without the set back. If you did what was that like.

I am getting ready to do major surgery to the deck to create a 3 seater so i was thinking long as i am into the transom surgery it would not be beyond me to cut a notch into the transom to give me the setback.

I have more time and experience with fiberglass than brains and money. Plus the extensions appear a little unweildly to me .

[The Hedgehog]

I would probably fool with drive height by using a shorty or maybe a setback box. Those can be undone.

The shorty has been done numerous times. I would love to see someone try the extension box on an 18.

[Lenny]

Lenny did you run your boat at all with the raised dimension without the set back. If you did what was that like.



Yes, as did Buizilla a million times. 65 was the number. The setback (8" extension to the drive) gave me the speed gains and more bow lift that was not available from the short drive previously.

[tommymonza]

Like i said more lack of brains and money and more fiberglass experience and time justifies the notch over the extension.

The transom and stringers are probaly good but the boat sunk 16 years ago for a couple of hours and that and age has me a little concerned.

The transom needs replacing anyways so raising the x at that point is mute.

I have owned this boat for 15 years and it has never seen water.A divorice and living in a condo has kept the project stalled. But now i have aquired an air conditioned enclosed shop for free near my condo to work on it so i am going to take advantage of it and do everything to it.

[tommymonza]

Thanks Lenny. Like i said you guys are a wealth of info here.

[osur866]

Best I've done with a stock 6.2 320 hp is 73.3 in freshwater. This is what I ran at AOTH for a short stint. I gained about 3-4 mph with the shorty, pre shorty 320 hp in a 18 will get you 67-69 all day long in perfect conditions light on fuel 1 person you might bump 70. Steve

[fogducker III]

Although I DO agree with you Grizz I can say that my 2 3/4" raised X dimension, 8" setback, Alpha 1:5, Cleaver boat (18) runs 71 GPS at 5100 rpm with a 400 hour 1987 350 MAG carbed motor. ( Verified via GPS more than once. :yes: I have not had it out yet this year with its' "changes" yet to see where it ends up now.

This boat in no way had 300 HP available.

Jeremys' Scorpion 18 runs, to date, 77.3 GPS mph with the 2" shortie Bravo, 1/3 of a tank of fuel, 1' of chop, 1 person in the boat and a labbed 27" Mirage+. FACT


Just to clairify, this was at sea level/salt water, PERFECT conditions for the boat, running with the waves and touched that number for a few seconds before HAVING to come off the throttle and trimming down....:yes:

I have no problem with 75mph consistently, however, I had to give the prop back and don't have the $$$ for a labbed 27P right now........:frown:

Still using the 23P Laser II and run low 70's all day long.........:wink:

See ya Sat Lenny...........:boat:

[mrfixxall]

Your treading on really thin ice here. There are mixed reviews on this area. It has been said 10 mph with higher X, but that is on really faster boats 80 and higher. It is kind of like nose cones. Now a bravo drive with the same prop height as an SS is slower then an SS. Then there is handling. Here comes the can of worms. Everybody has theories and what ifs. Few have ever done it with NO other changes. That6 being said there is the flaw in data.

griz its a bravo drive..

http://www.donzi.net/forums/showthread.php?t=57968

[tommymonza]

What gives DC18 67.7 with a stock 300hp magnum the labbed cleaver or does he have a shortie on it?

[Lenny]

What gives DC18 67.7 with a stock 300hp magnum the labbed cleaver or does he have a shortie on it?


The third prop we tried was a Merc Cleaver, labbed # 48-88450, 14-1/4 x 23P. GPS speed was 67.7 at 5400 RPM. The boat definately picked up top end and the ride was smothe. I am considering a 25P but not sure if I will use a three or four blade. I have heard that the newer four blades are awseome and give all arround good performance.
Boat info is 18 Classic, 350 Mag (stock) Bravo One Drive with 1.65 gear ratio. Big Griz your imput please and anybody else also.

Cleaver, stock bravo...

[HOWARD O]

I meant you Donzi pro's. I know there is a wealth of expermentation and knowledge in the smaller deep v class over here than anywhere else.

What is the speed gain with a raised conservative X dimension.I am getting ready to do something with restoring my boat and would like to know if is worth it to raise the dimension. My boat carries the bow quite well and has just a tad more rocker in it than an 18 Donzi.I would like to raise itenough but not so far as to deal with full blown cavitation all the time .A little positve trim would be nice to still keep also.


Plus this little ciggie looks like a blast.80 mph at 5200 out of a 700hp big block.http://www.vimeo.com/4374769


Edit out the Donzi enough? :confused:

[mrfixxall]

What gives DC18 67.7 with a stock 300hp magnum the labbed cleaver or does he have a shortie on it?

all stock! and only 20 hr's on he boat..

[tommymonza]

Just sounds like a remarkable speed for a 300hp especially through a Bravo.I know a stock 260 gets you right at 59-60 with a cleaver so a 7.7 gain with 40 more horse sounds like a lot . Are thoses labbed props good for 2-3 mph than ?

[roadtrip se]

Jill's ran 74-75 on a good day and light fuel. Most other days, low 70's. Bravo XZ drive.

I rode with Steve at AOTH, and besides about getting run over by the crowd, I did like the way it landed and handled with the shorty. Much better than the stock length drive on our Scorp.

[MOP]

The specs on the Chris may not be all that close, the reason I say that is we had Chris as a dealer those early to mid 80's boats you could get a suntan working inside of them they were thin. Most of you are to young to remember the rash of re-calls on the bottoms cracking, cracking was not the word hit a big wave and put on your life jacket they would have big splits! Pretty little but somewhat scary boat, I would keep it in a nice lake!!!

Phil

[tommymonza]

I was not going to bring it up but we had 2 of the 26 Scorpions sink in the early eighties by us because of hull failure.That was back when i used to boat in Holland Mi.

[tommymonza]

By the way what is AOTH ?

[HOWARD O]

By the way what is AOTH ?


http://www.mwdonziclub.com/awakening.html

[Classic Doddy]

Best I've done with a stock 6.2 320 hp is 73.3 in freshwater. This is what I ran at AOTH for a short stint. I gained about 3-4 mph with the shorty, pre shorty 320 hp in a 18 will get you 67-69 all day long in perfect conditions light on fuel 1 person you might bump 70. Steve

I have a 2004 with the 6.2 and I can hit 65 with the 1.65 drive and a labbed 4 blade cleaver (24p). what is your drive ratio and what pitch prop are you turning. Do you have any ill effects with mirage plus coming to plane with the shorty?

By the way... I love beating big 25 to 27 outlaws with their big blocks.

Thank-you.

Dodman

[RBT]

I have a 18c with a Alpha ss and a stock 23 merc cleaver prop. The motor is a 400cid, no clue on the power, but it is very mild. I am going to guess right around 300. I have only had my GPS in the boat one time and it ran 68.7 on (it runs mid 70's on the speedometer) with a full tank of gas in glass calm water, add the the silent choice had an air leak. I feel that under the right conditions and some prop testing it would run 71-72. It is an older boat that was poorly restored.

[Rootsy]

425 ponies and an Alpha SS in an 18 will embarrass CarlC...

[cutwater]

425 ponies and an Alpha SS in an 18 will embarrass CarlC...

Actually it would embarrass 95% of the boats on this forum, including mine. Which, incidentally, is the same percentage of threads on this forum that contain the word "carl"...