wrong prop?

metal249

Seaman Apprentice
Joined
Jun 7, 2008
Messages
48
I have a 1986 SeaSwirl 17' bow rider(3.0L omc) with a whaletail. I took it to the lake for the first time and it ran very sluggish. I could only pull 3400 rpms out of it, and it was very hard to get it planed. The full throttle operating range on the motor is supposed to be 4200-4600 rpms. I've already checked the points, cleaned the carb, checked the fuel filter and I put the correct octane fuel in the tank. I tried to check the timing but the light was broken, or the timing was way off and I could not find the mark on the damper. The motor was rebuilt 2 seasons ago and I do not hear any pinging or knocking. When I looked at new props, the suggested sizes were 13 1/4 X 19 and 13 1/4 X 21. The boat has a 13 1/2 X 17 on it and is a little chipped. There is also a little vibration when at lower speeds. Could the prop be the problem, or is this an engine problem?
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: wrong prop?

A 17P prop sounds about right. I think the vibration you are feeling is an engine miss. Check compression, make sure you have spark on all cylinders and without a tune-up, you have no base line. Just don't start throwing parts it. Diagnose and then repair whats broken. Doing otherwise can get expensive and frustrating.
 

metal249

Seaman Apprentice
Joined
Jun 7, 2008
Messages
48
Re: wrong prop?

Recent update to my problem, maybe helpful information. Just ran the boat and I'm getting ready to check the timing. The motor is running great except between 2000 rpms and 2500 rpms, there is a vibration. The vibration immediately smooths out at 2500 rpm.This is just running it in the yard, there is no load on the motor.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: wrong prop?

If there was no spark on number one cylinder timing light wouldn't work.
A miss would cause a vibration.Pull one plug wire at a time and check reaction.
If you pull wires at the distributor shocks are less likely.
 

metal249

Seaman Apprentice
Joined
Jun 7, 2008
Messages
48
Re: wrong prop?

I found the timing finally. It was advanced so far I just couldn't see it. The timing was supposed to be at 6 above TDC and was really at 24 to 30 degrees above TDC! I moved it down to 5 above TDC and adjusted the mixture as was needed. It now idles at 500-600 rpm but is a little rough. Does the timing being so far off explain my lack of rpm?
 

metal249

Seaman Apprentice
Joined
Jun 7, 2008
Messages
48
Re: wrong prop?

Just got back from the lake. The boat ran even worse. I could only get 2800 rpms out of it, while taking one minute or more to plane. With more than one person on board, I couldn't even plane it. I'm lost at this point, I know this boat is supposed to run much better, but I don't know what is wrong. Anyone have similar problems?
 

metal249

Seaman Apprentice
Joined
Jun 7, 2008
Messages
48
recent update

recent update

I believe this is a bad engine miss. I have to advance the timing just to get it to idle. Checked the mechanical advance in the distributor, and it appears to be functioning fine. I sprayed it with WD-40 just to be sure.
 

Robj

Lieutenant
Joined
Mar 22, 2007
Messages
1,441
Re: wrong prop?

Repost in the engine section. You will get a better response there.

Have a great day,

Rob.
 
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