running on water muffs merc260/alpha 1

[rtmt91]

I was running on muffs and noticed no water in the prop exhaust.
The water was exiting through ports on each side of the transom plate.
These ports seem to be inline with the exhaust bellows. I feel/smell exhaust from the prop but no water. I look in my SELOC manual and can not find any mention of these ports. I does mention a exhaust separator but not what it does.
One mech I spoke with said that what I was seeing is normal and water through the prop would be seen after it was in the water. And another said I should see some water at the prop.

So can any one help with my confusion. Does it require back pressure to water in the prop exhaust?

1989 merc/260hp, alpha one

 

[SuperNova]

Re: running on water muffs merc260/alpha 1

Those are exhaust ports as well. I noticed on mine the water will usually come out those two small ports until it warms up, then it comes out of the prop more. Also if you increase the idle a little it'll push more water out of the prop. But either way I think what you are seeing is pretty normal.
--
Stan

 

[Haut Medoc]

Re: running on water muffs merc260/alpha 1

Normal, as long as you are not having any performance issues......​

 

[rtmt91]

Re: running on water muffs merc260/alpha 1

Thanks for the info.
Can someone explain how this works.

 

[Haut Medoc]

Re: running on water muffs merc260/alpha 1

No great mystery....
The exhaust water is not getting past the aformentioned holes.....
Tip the bow of the boat up more & you will get water out of the prop....
It has nothing to do with backpressure or anything like that on land......​

 

[Don S]

Re: running on water muffs merc260/alpha 1

When the boat is in the water, and at idle, there is too much back pressure on the exhaust to run the exhaust thru the prop. So they designed exhaust relief ports in the transom shield.
Out of the water, the water runs out of those holes before it ever gets to the prop.

 

[sarantis]

Re: running on water muffs merc260/alpha 1

Check my recent thread "gm305 temperature problem".Maybe it's important for you.In my A1 the water from the prop now is about the same quantity as that of a transom hole.

 

[paultech6]

Re: running on water muffs merc260/alpha 1

Running an engine on muffs really wont tell you if you have a good impeller . Remember you are feeding it under water pressure thru a hose.
You should run it in a barrell thats deep enuff to cover pickup holes on the lower unit to see if the pump is really sucking up water.
The above post that states about the relief holes on either side is correct. . You will see more water come out there than the prop