Propping Twins Preference/ Theory

[roscoe]

Say I have a boat with twins. I/O or outboard, doesn’t matter. Boat has adequate power, but is not a high speed cruiser. Used for cruising the Great Lakes.

The question:
Would you prop for max rpm and performance, or would you prop with lower pitch, so the boat can get on plane in the event that one of the engines fails?

The question can to mind when I read this thread: https://forums.iboats.com/threads/propless.768284/#post-5876266

Your opinion?

 

[tpenfield]

If you have ever tried to get a twin engine boat on plane with one engine, you will realize that it may not be possible even with a lower pitch prop.

If you did find a low enough pitch prop to do so, in normal operation, it would easily over rev the engine.

So, if you prop slightly lower than the optimum, it probably won't be low enough to get the boat on plane.

I ran my twin engine boat with one engine and all it would do is 10 mph . . .

 

[alldodge]

Prop for max RPM
As Ted said your not going to get on plane with one motor no matter what. Even if you lift the drive full out the boat will not handle very well at all.

 

[roscoe]

That’s what I thought.
So if one fails, limp home.

 

[Scott Danforth]

Prop for max. Idle back on one