What's the Difference?

[GreyGoose006]

Does anybody know what the difference between marine and non-marine engines are. marine engines look like they are cheaper, but i was wondering why they are specified as marine use only. the ingines i am looking at are all pre-emissions chevy 350's, so emissions shouldnt be an issue.

[TheSilentChamber]

I think for marine use you can still use leaded gasoline.

[curtis73]

The main differences are easily overcome. Some are fine for automotive use and others need to be addressed.

Internally, they are usually really beefy. Marine engines spend 90% of the time at 90% throttle. Automotive engines spend 90% of their time at 20% throttle. Marine engines often have forged cranks and rods on four-bolt mains. Internal parts are often heavy; sometimes the pistons are tall, four-ring slugs. Oil pumps are usually high-volume. That is great for a 5000-rpm torque motor, but not good if you want a screamer.

Externally you'll need to do some things. Carbs on marine engines will work with some modifications. Vent the bowls, re-jet them, etc. Marine ignitions often have no provision for vacuum advance and they have a very different advance curve, so you'd have to either alter it or use an automotive version. Cams are designed for low-rpm use. Many of them peak their hp at 4800 or less. You might want to select a better cam for acceleration.

Otherwise, you'll need some parts. Flywheels and starters are different, intake manifolds can be used, but they have many alternate passages that may need to be plugged.

[KiwiBacon]

Some marine engines even turn backwards.

[2.2 Straight six]

don't some also have a special valve or something in the intake so water can't get into the engine?