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pcmpete
08-11-2010, 12:47 PM
Hi all, I don't own a Donzi but love this site.
I have a 16ft Tahiti I/O that has a Volvo 4 cylinder motor with a 270 outdrive. My plan is to change this power plant to a Ford 302 and 280 outdrive. The 302 came out of a Glastron and has log style manifolds with 90 degree risers (which just go straight down).
I want to turn my Tahiti into a 'Sweet 16' style boat with the 302.
I am changing to 4bbl intake and carb, center riser manifolds and a thru-hull exhaust. Which should help reduce some weight.
The 302 currently has '302' heads, would I see much difference if I upgraded to GT40/GT40P heads?
With the boat weight of less than 2000lbs could I put a mild/wild cam in it and still have a decent hole shot and good top speed?
With an outdrive ratio of 1.61 what size of prop would best suit this setup?
All thoughts and opinions are most welcome.
Thank you
Pete

BigGrizzly
08-11-2010, 02:04 PM
I personally would not do it, not enough gains.Prop is easy one of my 19 or 21 depending on hp

pcmpete
08-11-2010, 02:25 PM
currently it is 190hp, but after 4bbl carb and GT40P heads 'should' bring it up to around 240ish

BigGrizzly: why not? :frown: and what is the price on your props?

BigGrizzly
08-11-2010, 06:24 PM
The heads by them selves with the carb, won't yield that much. My props are in the $400 range

mphatc
08-11-2010, 07:32 PM
I have a ported set of GT40P heads FS , double valve springs, and resurfaced, to raise the CR . . The Logs will work fine, until you start adding a big cam . .

Mario L.

maddad
08-11-2010, 10:00 PM
The valves in the back of the motor hate log type manifolds.

BigGrizzly
08-12-2010, 09:27 AM
Mario's are a good deal, if he does this like every thing else he does. He is a stickler about every thing he does. Now to answer Maddad's post. He is correct if you use a big cam. There are some center riser manifolds available. PCM and OSCO are some.

pcmpete
08-12-2010, 10:50 AM
Mario, PM sent

BigGrizzly, I plan on the center risers, how big of a cam would you go without having side-effects?
and
what type of props do you have?

Thanks for the advise guys.

BigGrizzly
08-12-2010, 11:04 AM
Actually with a 302, fairly good sized The one thing to be a where of going too big and putting too large a carb on it. Forrest has a great running 302 with only 400+ CFM carb. I believe he ran a Crane 272 cam

pcmpete
08-13-2010, 03:23 PM
Actually with a 302, fairly good sized The one thing to be a where of going too big and putting too large a carb on it. Forrest has a great running 302 with only 400+ CFM carb. I believe he ran a Crane 272 cam
i just read another post by Forrest about his setup and this is a good plan for me to follow.
Thanks for your input BigGrizzly

BTW, the budget 302 that I built for my 70 mph 1972 16 with Mercruiser Alpha SS, puts out about 290 HP. It consists of a 1991 Ford 302 flat-tappet block and cast crank, stock open-chamber 69cc heads (intake gasket matched), KB116 dome pistons (9.4:1 CR), Crane H-272-2, Edelbrock Performer 289 intake, Holley 450 CFM vacuum secondary carb, half-closed cooling-systen w/160-degree thermostat, Kodiak aluminum exhaust and risers.
__________________
Forrest