View Full Version : Car motor or marine motor

10-16-2000, 12:30 PM
" i bought a 24 foot searay with a 305 v8 the motor was locked up!so i replaced it with a 350 chevy v8 bored 3o over,8.5-1 compression,600 cfm {edelbrock carb marine}.the boat will not plane off!the motor will only run 2200rpm's!! in the car i had it in i could run up to 7500 rpm's?is there that much diffrent from car motor to marine? "

john smietana
10-18-2000, 09:51 PM
" Did you change reduction gear,sounds like engine
overload,even with much increased hp.going from
1 1/2 or 2 to 1 to 1/1 could well cause this
problem.If you changed props.to much diam. and
or pitch could be the problem.Ck.exhust temp.with
engine under full load if overload is the prob.
temp.will read very high.Operating the engine at
full throttle even for short periods will!! cause
it to break.
After thought,retarded ign.timing also possible cause, "

10-19-2000, 01:22 PM
" no i all did was put a car motor in,the motor that was in the boat when i bought it was locked up.i have only changed the motor ,i dont know how many rpm's the boat ran with the other motor becouse i bought the boat not running,thanks for the help.it has a volvo outdrive if that helps anymore "

Craig Comeaux
12-11-2000, 11:09 PM
" Jason, unfortunately ther e is a wide difference from car to marine due to the extreme load on the motor. John is correct. You need to change the reduction gear and cam when switching to marine.
It is also a possibity that the timing and /or water distribution is off. There needs to be correct water flow into the engine and through to the upper end of the manifold and out to the water jackets in order to achieve thorough cooling of the motor. What is the temp reading? Also, many readings are incorrect due to the location of the temp stem locations.
Most likely you'll have to have the motor pulled and rebuilt. Make sure that you take it to a marine mechanic who will address the water flow situation. Craig "

04-19-2002, 11:59 PM
" sounds to me like you have WAY to much Cam....you don't have alot of compression to support that much cam.... you need to build torque,+ power down around 5000+rpms.....7500rpm is WAY out of the "boat" ballpark... "