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View Full Version : Wanting to SuperCharge my '76 2+3



pipnit
12-14-2010, 04:22 PM
Hey guys,

I have a 1976 Donzi 2+3. It has a SBC (now a 355 at 9.5:1 compression) and the TRS drive. Little by little I do work on it. One year it was rebuilding the engine, another year was to re do the interior and last year I repainted it the original color (Orange with White Stripe and blue pins). Now I want to get some more Ommph out of the engine. I run about 60mph at 5500 rpm and need more! I've played with the prop a bit (don't know what the tune is off the top of my head but it's a 4 blade semi clever intimidator from Hydromotive) but I think I'm slowed down by the monster drive. I don't want to change the drive and was thinking a good way to get some more horse pressure is to add a super charger. Any suggestions on what would fit and work well with my power config and boat?

Thanks in advance!

gcarter
12-14-2010, 07:37 PM
Poodle runs a SBC NA w/a TRS and goes about 80.
Is that enough?
I like NA engines. Keeps it simple.
You don't have a lot of extra room in there w/the tranny pushing the engine forward.

pipnit
12-15-2010, 10:03 AM
Poodle runs a SBC NA w/a TRS and goes about 80.
Is that enough?
I like NA engines. Keeps it simple.
You don't have a lot of extra room in there w/the tranny pushing the engine forward.

Really? Thanks, I'll track him down. Do you happen to know what he did to his engine to get it to do that? Of course I want the best of all worlds, re: be able to run pump gas.

BUIZILLA
12-15-2010, 10:41 AM
Hey guys,

I have a 1976 Donzi 2+3. It has a SBC (now a 355 at 9.5:1 compression) and the TRS drive. Little by little I do work on it. One year it was rebuilding the engine, another year was to re do the interior and last year I repainted it the original color (Orange with White Stripe and blue pins). Now I want to get some more Ommph out of the engine. I run about 60mph at 5500 rpm and need more! I've played with the prop a bit (don't know what the tune is off the top of my head but it's a 4 blade semi clever intimidator from Hydromotive) but I think I'm slowed down by the monster drive. I don't want to change the drive and was thinking a good way to get some more horse pressure is to add a super charger. Any suggestions on what would fit and work well with my power config and boat?

Thanks in advance! I think, at the very least, you need an additional 2" pitch, if not 3, for starters... 60@5500 is very inefficient, poodles is a 383-425hp/TRS, runs 78 with a crazy prop or 74 with a 4 blade Hydro in limo comfort, in fact, his engine is 20' from this 'puter...

mrfixxall
12-15-2010, 10:56 AM
I'm with Buiz,that hydromotive prop may be slowing you down,if your going to run a hydro prop you need to run the one that is for a outboard motor..they seem to work better on the donzi's.I would at leaste try a mirage + or a turbo one first before you add a blower..

pipnit
12-15-2010, 10:59 AM
Thanks Buiz,

Maybe I should try to tweak more, what I have right now. I'm going to get all the info on the prop which I'm running and post it up. I hope Hydromotive keeps track of this info, I'm sure they do. I went with thier reccomendation. The trs has a 1:1.5 I believe and the motor should be doing somewhere close to 400hp, "full roller" 355 at 9.5:1. Thanks again, I should have gleaned more from this site last summer. Another thing that I haven't done is really played with the carburation. What is the ideal fuel to air ratio on a boat like this and what would be the correct way to measure it?
Thanks again for the info.

pipnit
12-15-2010, 03:36 PM
Ok, well this is what I have,

It's an OT prop quad 4 from Hydromotive, what they would put on an outboard or high performance bass boat. The diameter is 14.750" and the pitch is 20. According to Hydromotive, I'm getting 13% slip. Suggestions?

gcarter
12-15-2010, 03:59 PM
22"-23" like Buiz said.
A few years ago I had a Minx (20') with a similar engine and prop but a 22" pitch, and on a good day it would do about 65 MPH @ 4600-4700 RPM.
An 18 is more aerodynamic than a Minx and also lighter. It's normal for an 18 to perform better everything else being equal.

pipnit
12-15-2010, 04:11 PM
22"-23" like Buiz said.
A few years ago I had a Minx (20') with a similar engine and prop but a 22" pitch, and on a good day it would do about 65 MPH @ 4600-4700 RPM.
An 18 is more aerodynamic than a Minx and also lighter. It's normal for an 18 to perform better everything else being equal.

Cool, I'll have to try this. Got a prop you want to sell? :)
I was talking with Todd (I think that's his name) at Hydromotive and asked where the boat makes power. How the hell should I know. Right now I can spin at 5500 for quite a while and it doesn't get hot, i just get nervous running wide open for extended periods of time. He said that you want the SBC to spin and not lug so going to a higher pitch wouldn't help. I'm skeptic and encouraged with what I'm being told here. Any suggestions on what prop I should get? Thanks again!

OFFSHORE GINGER
12-15-2010, 05:29 PM
Hey guy if you are having a problem spining the right Blade give Julie a call at Throttle up propellers at 727-531-2255 she really knows her $hit .

BUIZILLA
12-15-2010, 06:15 PM
What instrument did you use to determine the 60 mph #?

yeller
12-15-2010, 06:47 PM
Hey guy if you are having a problem spining the right Blade give Julie a call at Throttle up propellers at 727-531-2255 she really knows her $hit .I dealt directly with Hydromotive when buying my prop. I thought...who would know better; the manufacturer or a retailer. Well I was wrong. Deal with Throttle Up. You'll get more accurate information. Julie is great.