Mercruiser prop question

Hello, I am a newbie to this forum so please excuse me if I do not proceed correctly. I have a 1965 18 1/2 ft lapstrake wood boat similar to a Thompson. It came with a 110 hp GM engine known as an "iron duke" with an outdrive called a "Mercruiser One" I do not know the gear ratio. For a number of reasons I have replace the complete outdrive (brackets, gimbal ring, flywheel adapter, etc) with a complete 1986 Alpha one from a 16 ft Sea Ray with a 3.0 liter engine. Again I do not know the gear ratio. The prop on the alpha one was junk. I have mounted the prop from the old outdrive on the new outdrive. The only prop serial number I can find is 48-56014-19 and a spare Michigan prop with number 0310.3. Can anyone tell me if the gear ratio is different and if it is how much do I need to flatten the pitch to accomodate the lower hp of my older engine? thanks

 

The prop number sounds like a 14" x19" (D x P), very common for an Alpha 1 with an 3.0 engine. You easily find more details at iboats.com .

I do not think anybody on this forum is equipped with paranormal perception (although some may think so themselves), so you will not get a reliable answer as to the gear ratios. But is it important?

It would not surprise me if the prop would be suitable for your boat or perhaps a bit too steep. A short test run will provide the answer.

 

The 3.0 is a 140HP engine. You have the smaller 2.5 and may need a lesser pitch propeller.

 

Sorry I guess I have to differ although I admit I know very little about it. The valve cover on the larger engine and the alpha one outdrive both say 3.0 liter on them and the spec plate on the valve cover says the engine is rated at 130 hp. The prop on the alpha one was a junk 15d x 17p

 

You posted it says 110HP.

 

you might be lucky
with my paranormal crystal ball I can see your old 110 had a 1.98:1 ratio and there's a 99% chance so did the late model drive.
the 19 inch prop will be close....

 

That would be the standard reduction for a 4 cyl.