Prop question

firedude

Cadet
Joined
Jan 21, 2009
Messages
6
The setup; I have a new 20 ft glastron bowrider, 4.3EFI MPI Mercrusier with the Alpha 1 drive, recommended WOT is 4400-4800 rpm. The boat came propped with a 14.5x19 pitch alum. We typically will only have 3-4 people at any given outing. The 19pitch aluminum prop easily hits 6800 rpms, well beyond the WOT. I went back to dealer, they let me try a 21p, and it dropped the rpm to 6000rpms, The difference in hole shot and top end speed, was negligible, now I need to go back and see if they have a 23 pitch to try, this should bring me closer to the recommended WOT. Now for the question, the paperwork with the boat noted the boat should be matched with the correct prop from the dealer so the WOT can be achieved, as I see it the prop that came with the boat was not the correct prop, do I have valid argument where I should insist that the dealer provide me with a different prop. I certainly do not want to run a prop that goes way beyond the WOT, whereas it would void the warranty. The more I speak with the dealer, the more I get a feeling that they do not want to make this right. Any productive thoughts would be appreciated
 

littlerayray

Lieutenant
Joined
Feb 17, 2013
Messages
1,456
I would phone mercruiser customer support and explain to them the problems the marina is giving you
 

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
i wonder if your tach is set to 4 cylinder - if you take 6800 and divide it by 6 and multiple by 4 you get 4600 - you might be right on and your tach is not showing right stuff. There is a selector on the back of some tachs. I doubt you can get a 4 stroke to hit 6800 - it would be falling apart. I would be a little leery of your dealer.
 
Last edited:

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
If tach is healthy and well set, dealer sent a prop for max stated number of passengers or load which should be more than 3-4, right ? if so, while boating lighter prop is achieving more rpm than needed.

Happy Boating
 

madolive3

Petty Officer 2nd Class
Joined
Sep 2, 2011
Messages
120
My first thought was, Check the Tach. I'm having some of my own tach issues right now.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Did the dealer ask you about your typical load? 19" does seem undersized for a 220 hp 4.3. But I agree I think the tach is set wrong.
6800 rpm calculates to over 66 mph.
There is no doubt in my mind that a 19 will over rev possibly even with 4 aboard. but 6800 indicates the tach is set wrong.
You have to wonder who tested the boat no doubt it would over rev with only one aboard and a 19.But it would be a much more reasonable number.
By the way did you follow break in procedure?
 
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