maybe a prop question 4.3L mercusier alpha one

Boatguy4607

Recruit
Joined
Jul 19, 2017
Messages
5
Facts:
92 celebrity BR 190
Unloaded weight 2550lbs
4.3L mercusier engine
Alpha one outdrive.
Missing facts:
Prop pitch
Wot speed

Typical load is 4-6 people with 4 people including a tube or skiers. Now without towing anything I am at 3800 Rpm with 4 and 3950-4000 just one person. Now that's kinda concerning knowing that the normal operating wot of a mercuiser 4.3L is 4400 to 4800. Not sure if I am just grossly underproped or if there's a gearing issue or if it's an engine issue. Could a really bent and chipped prop contribute to loss of rpm? Any help would be great. Let me know if you need any more info. If I had to guess probably 30-35 is the wot speed.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Hi

What prop is on it.
With the figures given....and the engine etc being presumed healthy....you are over propped, not under propped.
Really need to know what your current prop is and drive ratio stamped on the drive.
 

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
Welcome aboard! :welcome:

Yes, a badly bent/chipped prop will impact performance, including WOT RPM.

Make a couple of more posts, then post a picture or two of the prop.
 

Boatguy4607

Recruit
Joined
Jul 19, 2017
Messages
5
It has taken me this long to remember to look for the numbers. My prop is a 3 bladed 14x19p. So from what I've gathered it is about average, out drive is a mystery. . With three smaller people, minimal cargo and almost no gas the WOT speed is 36mph at 4000rpm, properly trimmed. That is indeed very low bit then again, out prop probably shouldn't even be put to WOT. I would like to see an improvement to around 42-45mph at 4500-4700rpm. The engine had a tune up in may. I'm trying to share a google album with pictures of our prop. (I'm like really embarrassed). If you think a new prop would solve most of our problems then that's what I'll do.

https://photos.app.goo.gl/yscP3GVjQsxhegz03
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
the WOT speed is 36mph at 4000rpm,

Ayuh,..... Welcome Aboard,.... Yer Right, that prop is pretty beat up,....

I'd try a 17" pitch, 'n see how it changes yer performance,....

If the rpms at Wot come up to 4200/ 44400 rpms, I'd keep it as a spare, 'n buy a 15" prop to run,....
That oughta get ya closer to 4800 rpms which is Perfect for a ski boat,...
 

Boatguy4607

Recruit
Joined
Jul 19, 2017
Messages
5
Theres a used 14x19p prop near me. It looks as though it have barely been used. Would it be beneficial to buy that first and see where that takes me?
 
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