Logo

Repowering w small block chevy alpha or bravo outdrive

masterbaiter88

New member
"hello to all, i am repowering

"hello to all, i am repowering a 1973 seabird 23 foot boat from twin 4 cylinder omc to single small block chevy. the transom and stringers are out. im in the process of surface preping the hull. i am planning on replaceing the stringers with mahogany. if figuer this would be best to handle the v-8. i also figuer i better ask before i buy materials. i hope to find a rotted out boat to get the motor and outdrive. question 2 witch outdrive do i look for? this boat will be used for fishing off shore ponce inlet. and i plan on in time building the motor to 330hp.
i got pics of the project just need to figuer out how to post them
thankyou, mike"
 
Alpha drive is only rated to 3

Alpha drive is only rated to 300 horsepower. 330hp is a lot to squeeze out of a small block and use for extended time. I run a 21 foot Searay about 300 hours a year fishing. It is powered by 260hp with alpha drive. weighs about 4500 pounds loaded with a 20% deadrise at the transom. I run 24 knots at 3200 rpm. Burn about 11.5 gallons per hour. Extremely rare for me to run the engine past 3300 rpm. Fuel consumption goes up quickly above that. I am about to build a new engine targeting peak torque at 3200 rpm. High revving high horsepower engines don't last very long and burn lots of fuel.
 
"Ayuh,...

If you're rep


"Ayuh,...

If you're replacing the Stringers,+ Glassing them in,...
Mahogany is a WASTE of Money...
3/4" Plywood is More that sufficient...

And,.., At your target Horsepower,...
A Bravo would be a Wise Choice..."
 
"Ayuh,...

Alphas are the do


"Ayuh,...

Alphas are the dog-clutched drive, rated to 300hp...
The Bravos are cone-clutched,+ rated to about 400hp...
Alpha drives weight about 85lbs...
Bravo drives weigh about 100lbs..."
 
"Bondo is right about the stri

"Bondo is right about the stringers. I went a step further on my rebuild and used 2"X8"s for the engine and fuel tank stringers. I beveled the bottom of them to fit the hull's contour. Then I used exterior grade plywood in front of them. After you cut & fit all your stringers, transom and floor, treat them w/CPES (google).

Remember to allow 1/4" more room for fiberglass work when fitting the fuel tank between the stringers. I moved my new tank back more toward the stern since it had rear hose fittings. The engine mount blocks can be made from a 6"X6" block of hardwood also treated w/CPES after you drill pilot holes for the engine mount bolts.

Shoot me an email if you need more info, have questions or want to see some pics of the work."
 
Back
Top