What RPM should my engine run @ WOT?

hydro556

Seaman
Joined
Jun 9, 2007
Messages
64
I have an 82 Merc 5.7 260 HP with (I think) a Mercruiser "1" drive. I havent stayed in it for a real long time but it seems to top out around 3900 RPM. Peak power, from what I read, is 4300-4600 RPM. What do you more experienced guys think I should be running?
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: What RPM should my engine run @ WOT?

4200-4600......;)
What size prop are ya runnin'?......
Have you dowe a compression test recently?......:)
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: What RPM should my engine run @ WOT?

At 3900, you are lugging the engine. Best to be within specs for best engine life. The boat will plane easiest when at propped to the higher side of the range.
With the engine tuned up, clean bottom, at normal weight (including fuel) and at best trim, and a good prop (not one all nicked and gouged and bent) then run it and find out what the WOT is.
 

hydro556

Seaman
Joined
Jun 9, 2007
Messages
64
Re: What RPM should my engine run @ WOT?

The prop looks brand new, not sure what pitch it is. I havent done a compression check. Engine idles smooth, and has excellent power, seems to be in perfect running order. I guess I could take it to a shop and have it checked out. Got an issue with the blower that I am having trouble diagnosing anyway. It runs at a low speed constantly unless I pull the fuse. If I turn it to the on position, it runs at a faster (normal?) speed. but in the off position it just runs, slowly. I think it is in the switch. The switch is a 3 position switch. To the left, the blower comes on, to the right, the bilge pump and in the middle it is supposed to be off. Anybody know where I can find a replacement switch for an 82 Glastron Sv-191?
 

hydro556

Seaman
Joined
Jun 9, 2007
Messages
64
Re: What RPM should my engine run @ WOT?

What is required to check compression? Just a simple gauge that screws in to a spark plug hole. I could do that myself.
 

Manipulator

Senior Chief Petty Officer
Joined
Apr 11, 2005
Messages
743
Re: What RPM should my engine run @ WOT?

I have a 5.7L/260HP and I get about 4100-4200 WOT. I have a 14 3/4 inch prop with a 17 inch pitch.
 
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