1987 22' Sylvan Offshore prop?

[1987sylvanoffshore]

What is the original prop size? It's an Alpha one gen one with a 140HP 3.0L.

Thanks

Mike

 

[skyking897]

Re: 1987 22' Sylvan Offshore prop?

I've got an '86 offshore, same engine. I think it,s 13?" X 19-21 pitch. I'll check my prop on the weekend and get back to you.

 

[skyking897]

Re: 1987 22' Sylvan Offshore prop?

Sorry I didn't get back to you sooner, just checked my prop today. It's a Michigan 31023. If I looked it up right it's a 15 1/4 X 15.

 

[jkingry1]

Re: 1987 22' Sylvan Offshore prop?

Mine has a 14 X 19 aluminum on it.

 

[1987sylvanoffshore]

Re: 1987 22' Sylvan Offshore prop?

Thanks for the replies, I think the 15 1/4 is the correct size from the factory but just wanted to make sure. jkingry1 what are your rpm's at WOT? I have a 19p aluminum and the WOT is too low. I guess a better question would be what the rpm's are on the 15p prop. I think our boat should be between 4200-4600 at WOT?

 

[jkingry1]

Re: 1987 22' Sylvan Offshore prop?

Well 1987,

Would love to answer but the tachometer has been broken since I bought the boat. I have a new tach now and will report back after painting and installation. I will say the boat runs 32 mph with a pretty badly chewed prop, full tanks, and me.

 

[1987sylvanoffshore]

Re: 1987 22' Sylvan Offshore prop?

From what I have read our boat should be at around 40 - 42 mph with gear, people and fuel. I going with the same prop as skyking.

 

[jimbo_jwc]

Re: 1987 22' Sylvan Offshore prop?

Mine Thompson 1987 3.0 L 130hp MCM MERCRUISER Alpha One 14.5" 17P 3 Blade aluminium , reaches max and then some on WOT rpm but not sure why motor has two rpm #'s ? maybe diff gear ratio in lower units for diff brands models ? Different thermostat temps ?

48-78118-a40-17p prop so IT's 14.5" X 17Pitch still don't know if its cupped or not but was told its orignal