building my first marine engine

[jroach'sflyinhawiian]

ii have built car engines before but as the title states i have never built a motor for a boat before. i am using a 350 chevy car engine. do i absolutely need a forged crank and upgraded rods. or can i get by with a cast crank and stock car rods? engine is going in a fairly light boat and will be roughly 300 horsepower, maybe a little less if anything.

 

[Bondo]

ii have built car engines before but as the title states i have never built a motor for a boat before. i am using a 350 chevy car engine. do i absolutely need a forged crank and upgraded rods. or can i get by with a cast crank and stock car rods? engine is going in a fairly light boat and will be roughly 300 horsepower, maybe a little less if anything.

Ayuh,.... Marine motors are Truck motors, nothin' all that special,.....
No forged crank, No special rods,...

Cam it for idle to 5000 rpms,...
Hyper-pistons,...

 

[jroach'sflyinhawiian]

thats good to hear, in the hot rod communuty marine motors are revered as some kind of indestructible miracle. ive always been told they were forged everything.

 

[Fishermark]

ive always been told they were forged everything.

There's a lot of that misinformation going around about marine engines and their internals.

 

[Walt T]

Yeah but it's not a true marine motor til it's been blessed by Neptune himself. Seriously though if you're gonna build a motor spend a few bucks more and build a nice little stroker or something. Vortec of course. Nobody ever complained of too much power.

 

[Fishermark]

Bond-o already mentioned it... but it needs to be emphasized. If you are building this motor from scratch one of the more important decisions will be the cam. What works for power in a car is different than what you need in a boat. It needs to be simple without a lot of overlap. Your basic stock cam that came in a half ton truck is basically what you want. Or if you are ordering a cam - just be sure you do the research for one that builds power (torque) on the low end of the rpm scale. Your outdrive will not "allow" anything over 5,000 rpm.

 

[Bondo]

Bond-o already mentioned it... but it needs to be emphasized. If you are building this motor from scratch one of the more important decisions will be the cam. What works for power in a car is different than what you need in a boat. It needs to be simple without a lot of overlap. Your basic stock cam that came in a half ton truck is basically what you want. Or if you are ordering a cam - just be sure you do the research for one that builds power (torque) on the low end of the rpm scale. Your outdrive will not "allow" anything over 5,000 rpm.

Ayuh,..... Back in the day, if yer camin' yer pickup truck, ya went 'n bought an RV Cam,....
When ya got the cam, the tag that said RV, said Marine on the other side,....

If yer buildin' from scratch, 'n lookin' for the "Plan",...
Build yer HP with compression, 'n Vortec fast burn heads, 'n matchin' pistons,....
You'll need a dished, or inverted dome piston that mirrors the head,...
Shoot for right at, or just under 10:1,.....

A Stroker crank will Really up the ante,....

 

[Tail_Gunner]

thats good to hear, in the hot rod communuty marine motors are revered as some kind of indestructible miracle. ive always been told they were forged everything.

If your building a big block or high reving engine forged is the way to go...5000 and under cast is fine