What outdrive ratio for 89 25 Regazza ?

[Stillcrazy]

Handed down my 25 Regazza to my grandson to play with. The OMC stuff is gone and replaced with Mercruiser. The motor is a custom build 400 that is supposed to put out 300. Since originally you could purchase this boat with a 351 according to their old brocure, what drive ratio and prop pitch did they use ? I agree that it should have been a 454 but he has the 400, so what drive ratio ? He can't turn a 17" pitch ! Either the engine is bogus or the drive is to steep. What did Donzi spec.?

 

[Faztbullet]

Re: What outdrive ratio for 89 25 Regazza ?

Did you replace all the "cobra junk" or install a SEI conversion? The last one I did needed some major cutting as it did not have enough "negative trim under....

 

[Stillcrazy]

Re: What outdrive ratio for 89 25 Regazza ?

Hummm ? replied but not shown ? second try, excuse if this is a repeat. Complete replacement of the OMC stuff with Mercruiser. The "x" dimension was set to the upper limit but the problem as related to me by my grandson who lives 100 miles away, is that the engine won't power up. He says 2000rpm @ WOT and about 20 mph. with a 17" repitched prop. That sounds like lugging or the engine isn't making power. Got him checking the tune....Timing, carb secondaries etc. Either the engine is sour or the drive ratio is wrong. I think that the 460 turned a 16x19 prop.

 

[Don S]

Re: What outdrive ratio for 89 25 Regazza ?

What drive did you put in it, and what ratio is it?
With only 2000 max rpm, you have engine problem, not ratio/prop problems.

 

[Bondo]

Re: What outdrive ratio for 89 25 Regazza ?

Complete replacement of the OMC stuff with Mercruiser.

Ayuh,.... The question is, WHAT Mercruiser stuff,..??

If it was originally 454 Mercruiser stuff, ya might have too tall a gear ratio....
If it was Mercruiser stuff for most everything other than the 454, or a 351 Ford,...
Ya, you've got Serious motor problems....

The ratio used by Merc. for most V8s is 1.50:1, 'n if yer 400 ain't windin' to the Moon with a 17" prop,...
She's 1 sick puppy....

 

[Stillcrazy]

Re: What outdrive ratio for 89 25 Regazza ?

A "Donor" boat of similar size with a bad motor was used. Thus the "Custom" built engine. I am glad that you agree the engine isn't putting out.
Still curious if anyone ever bought the Small Block version ?

 

[Bondo]

Re: What outdrive ratio for 89 25 Regazza ?

A "Donor" boat of similar size with a bad motor was used. Thus the "Custom" built engine. I am glad that you agree the engine isn't putting out.
Still curious if anyone ever bought the Small Block version ?

Ayuh,.... WHAT motor,..??

Small block version of What,..??

 

[Don S]

Re: What outdrive ratio for 89 25 Regazza ?

You still didn't say what drive you have, or it's ratio. The words ( A "Donor" boat of similar size with a bad motor was used.) sure doesn't help much. If you don't know what it is, then post a picture of it.

 

[HT32BSX115]

Re: What outdrive ratio for 89 25 Regazza ?

Either the engine is sour or the drive ratio is wrong. I think that the 460 turned a 16x19 prop.

Howdy,


If you had an OMG 460 King Kobra in that thing, it had a 1.43:1 drive and probably turned a SS 15" dia x17p prop (OMC#391290)
Mine had a 19p cupped and repitched to 20 but my boat is shorter and lighter. (21' Four Winns)

If you put an SBC in it you should probably have a 1.5:1 drive and probably start with a 17 and maybe try a 19 depending on how it performs.


I would make sure that the engine is capable of making rated power before I fool with propellers though.....



Regards,


Rick

 

[Stillcrazy]

Re: What outdrive ratio for 89 25 Regazza ?

OK, you got me. The "Donor" boat was a 24' Wellcraft with a 350 Magnum, Alpha One drive of the same year. The color was white with red trim. The original motor "sank" because the owner died and the wife left the boat on a trailer with the bilge plug in and no canvas protection. If you are familar with South Fl. weather you can guess how long the battery lasted. It caved the trailer and she wanted to get rid of it. The original MERCRUISER 350 MAGNUM motor had water in 3 cylinders and the walls/pistons were beyond repair.The assumption was if a 350 Mag ran the Donor boat with that drive, it should push the Donzi especially since the 350 Mag was replaced with a 400, 4 bolt, with more horsepower. I felt that the weight being less than the OMG package and Hp close, it should work. The best fit would have been a 454 Bravo "Donor" which showed up 6 months later...of course. The specs were all given to my grandson and I'm really not sure of the ratio. I am assuming a 1.5 and getting screwed on a rebuilt engine.....but that is another story. I am still looking for the Original SB horsepower, ratio and prop. Just curios. For now I am settled in on a sour engine.

 

[Stillcrazy]

Re: What outdrive ratio for 89 25 Regazza ?

Theoretical 4450 lb boat with 300 hp gives a weight to power ratio of 14.83/1 and give a potential speed of 58 mph
Using a 17" pitch prop @ WOT with a 1.5 drive ratio, it should go 52 mph
So both seem reasonable.... IF you can get WOT

 

[Don S]

Re: What outdrive ratio for 89 25 Regazza ?

a 350 Magnum, Alpha One drive of the same year.

That, is what we needed to know. The Alpha I outdrive for the 350 engines typically used a 1.50:1 gear ratio. Different for high altitude.
The outdrives are rated for 300 hp max.
Prop pitch changes for each individual boat, there is no such thing as a certain prop for specific type boat.
Do some reading in the prop forum, and you will see what I mean.

 

[Stillcrazy]

Re: What outdrive ratio for 89 25 Regazza ?

I am sorry that you do not understand the question. Donzi sent me a copy of an original article about the 25 Regazza. In the article it mentioned that it was offered with a SB engine but was shown with the 460 King Cobra. My question then is, for that "specific boat" with a SB, what drive ratio was used ?
The issue of prop pitch was injected when information about the 460 ratio and prop were given as a helpful guide but it redirected the focus to the pitch of the prop and not the ratio. That however, did turn out to be helpful because it brought back attention to either the ratio or the engine when it didn't want to spool up with a 17" prop.

 

[Bondo]

Re: What outdrive ratio for 89 25 Regazza ?

My question then is, for that "specific boat" with a SB, what drive ratio was used ?

Ayuh,.... 1.50/1....