1978 3.7 / 470. Alpha one prop size?

[surchin]

Need to replace mine need a size. I'm not at the boat. I don't think it's stamped anyway. Anyone advise me on Diam and pitch so I can order one now? Install Friday?

Thanks
Scott

[twhrider2]

If not too late, I have same model boat and engine. Prop #48 88442A-4 21P in stainless. Hope this helps

[twhrider2]

Oops, just noticed you have alpha 1 mine is a pre-alpha 1:84 if it matters.

[spareparts]

21P is awful steep for that motor, how many rpm does it turn at WOT, I'd guess a 19P if you're just riding, 17 if you're pulling skiers

[twhrider2]

Not sure spare, have not had it in the water yet. PO "said" would do 38 on gps but not sure of rpm. May be another unknown to look into when splashed.

[Destroyer]

Originally Posted by twhrider2

Not sure spare, have not had it in the water yet. PO "said" would do 38 on gps but not sure of rpm. May be another unknown to look into when splashed.

I gotta agree with Spare on this one.. 21p is an awful steep pitch for that engine. I'd think a 19p in Alum or a 17p in SS would work better.

[surchin]

Thanks for intel! Update. Prop not stamped with any sizes. Existing prop is alum. Out drive is pre alpha can't find model no on it.

[surchin]

I'm in California ocean usually pretty rough so I cruise 3000 rpm 16-20 knt speeds not wide open. No skiers or that stuff