Running engine on muffs

[204 Escape]

Have a 5.0 Mercruiser. Wanted to check it out prior to going to the lake this weekend. How long can you run the engine on muffs ?? I don't want to ruin an impeller.

Thanx

 

[CobiaXL]

Re: Running engine on muffs

As long as you got water,run it all day on muffs.Just don't rev it over 3000 rpms.Keep eye on temp gauge too.

 

[204 Escape]

Re: Running engine on muffs

At idle will it get hot on muffs ?

 

[paultjohnson]

Re: Running engine on muffs

If you cooling system, impeller and stat are functioning properly, it should run the same temp on muffs or in the lake. If it gets hot at idle on muffs, its not because its on muffs, it is because there is a problem with your cooling system. If your impeller is failing, it may run cooler on muffs as it is getting its cooling water force fed to it. If it has to draw its cooling water from the lake with a worn/ old impeller, it may tend to run warmer. I think 3000 rpm is awfully high to run on muffs, It may try to draw more cooling water then the garden hose can supply, and then the hose may collapse cutting off flow altogether, thereby destroying your impeller, and overheating.:facepalm: my 02 cents

 

[04fxdwgi]

Re: Running engine on muffs

At idle will it get hot on muffs ?

As long as you have sufficient water flow thru the hose and muffs to the Raw Water Pump and engine, you should be able to run it all day long. Now, the drive on the other hand, may get warm, since there is no water around it to cool it off, but that will take a while to warm up. Ran my 454 engine on house water for 45 minutes yesterday to get a few things tweeked and ready for the weekend and manifolds were as cool as running in the river (or maybe a little cooler since the well water is pretty chilly). Drive did get warm, but nothing to even be concerned about.

 

[badkins50]

Re: Running engine on muffs

I always run mine on the muffs at home before taking it to the lake as a precaution. I lower the outdrive first, I don't know if it makes a difference or not but my thinking is it has to cause some stress leaving it up. Nothing more embarrassing than launching boat and parking truck and trailer to come back to the dock and your boat wont start!

 

[Icyharp]

Re: Running engine on muffs

I ran mine for a half hour yesterday on the muffs doing a little work before tomorrow, and never went over 2000 rpm, at idle or at 2000 rpm the temp stays at 140ish to 160. However what I have noticed is that the starboard exhaust manifold will get much warmer than the other, it does not do this on the river or lake only on the muffs, but I don't worry about it but am aware of it before I lean on it.

 

[Mike Zee]

Re: Running engine on muffs

My 89 5.7 does the same thing. It does hold a steady 140 deg. But i just put in a new thermostat. Starboard exhaust gets warmer, not extremely hot though.

 

[204 Escape]

Re: Running engine on muffs

Well, the temperature rose up to 200*, so I took it to the shop. THe impeller was bad. Changed it out, new lower gear grease, and emp came down to 150*.

Good thing that I checked it out.

Thanx, to all who offered advice/help !!!

204 Escape

 

[04fxdwgi]

Re: Running engine on muffs

Absolutely correct.... Never run engine with the drive tilted to trailer position.