questions about running on muffs

[IGeeky1]

So I finally got the boat out today. Could not get it to stay running at idle, would always stall. Also it felt underpowered throughout the spectrum. A bit noisy too, more of a thumpy noisy tahtn a tapping or clicking. I did check point gap and set timing prior to taking it out. I may not have any idea what I'm talking about but running rich came to mind.

So I'm going to need to run for a while on muffs while I try and figure this thing out. My SeaDoo XP on muffs should only be run for maybe 15 minutes. Is there a limit like that for my 1989 MCM (GM) 3.0L ?

I know there is a thermostat in the water path, I replaced it. So until the stat opens up where does the water from the muffs go? Can I get too much water or water pressure in or is it a safe system? When it is passing through the thermostat the water then exits through the center of the prop yes? I guess I'm a bit nervous...

Thanks

Mark

 

[nrasnake]

Re: questions about running on muffs

I've never heard of a time limit for these motors and I would expect there would NOT be one. There is a bypass channel in front of the thermostat which allows water to flow through until the thermostat opens. The water bypasses the thermostat and flows through the system the same as when the thermostat is open (you just don't get as much flow through the bypass, by design). You should just open the water supply valve enough to have a gentle full stream of water, but don't open it completely. You don't want full supply pressure on the muffs. Yes the water exits through the sterndrive/prop always. Nothing to fear as long as you ALWAYS have water to the muffs. Also, once its running check the supply hose and make sure it's not collapsed. If so you may need to open the supply valve a little bit more.

Good luck with getting it running right. Has the carb been rebuild lately? Is the carb adjusted properly? Is the fuel pump working properly? Is the fuel fresh and clean? Are you getting a good spark? Is the timing correct? Just some thoughts...

 

[bonzoscott]

Re: questions about running on muffs

Turning the garden hose pressure on "TOO HIGH" can make the muffs slip off or out of position, off the water intake - thus smoking your impeller. You may want to have someone watch and insure the muffs stay on until you learn what the ideal hose pressure is.

 

[spdracr39]

Re: questions about running on muffs

And don't rev the motor over 1500 and if you do rev it to 1500 do it only for a few seconds

 

[IGeeky1]

Re: questions about running on muffs

Thanks all!

 

[ktbarrentine]

Re: questions about running on muffs

When it is passing through the thermostat the water then exits through the center of the prop yes? I guess I'm a bit nervous...

Thanks

Mark

During operation on muffs (particularly at lower RPMs), most of the water comes out of the idle relief ports at the bottom of your transom mount (either side). Very little comes out of the prop.

For more info....see the service bulletin in post #4 of this thread:

http://forums.iboats.com/mercruiser...rives/bravo-2-water-flow-question-606939.html

HTH!