Prop pitch and diameter for mercruiser 3.0 alpha w alpha one outdrive

Ed Harris

Petty Officer 2nd Class
Joined
Jan 7, 2016
Messages
199
I had a 15.5 X 17 on the Wellcraft and got like 36 mph at WOT 4400 rpms. Switched it to the one mentioned above and it put a little more pressure on my engine. Still original motor. I noticed a little oil leaking from somewhere around the timing cover so this more pitch put a little more backpressure in the crankcase is what I am thinking. I only ran it up to WOT to see what it would do coming back to the launch. I spent most of the ride around 3100 to 3200 trimmed up running. I have pulled this motor once to rebuild the front motor mount box and dont really want to pull it again but if I have to at least it is not a beast of a job.
 

Guymontag

Seaman Apprentice
Joined
Oct 10, 2018
Messages
48
Do you think the 13.5 23p will be easier on the motor and able to keep me at 30 with a lower rpm? I ran it at 3800 rpm at 30 with the 14 23p at 25 -30 mph but if you guys think I could get the same speed at a lower rpm? What a pita other then buying each prop and trying them. Bit of a science balancing safe to. With top speed
 

TyeeMan

Master Chief Petty Officer
Joined
Feb 27, 2006
Messages
849
Ayuh,..... If that's actual rpms,.... that's Perfect,......

Meaning your 14 X 23 getting you 4800 Rs.

I wouldn't worry about it unless you're going to pull a tube or skiers. Don't worry about cruising speed, WOT speed and all the rest of it. Think of it as cruising RPM (about 3000, maybe a little less as long as your fully on plane) and WOT RPM.
 

Guymontag

Seaman Apprentice
Joined
Oct 10, 2018
Messages
48
That's what I mean if I'm at 3000rpm I'm only doing like 20 that's , point for the 3.0?
 

porscheguy

Chief Petty Officer
Joined
Jan 17, 2013
Messages
441
Where are you located? I’ve got a 23P Quicksilver lightspeed (laser2) I don’t use.

Yeah, unfortunately the only way to know for certain how a prop will perform is to buy it and test it on your boat. If you’re lucky, you can sometimes borrow them.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Sounds like a lovely boat but something is giving you wrong info for sure. The numbers don’t make good sense to me. Either your rpm gauge is out, your mph basis....or you have a 4.3 disguised as a 3.0, haha.
 
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