Don, Do I need to exchange exhaust gaskets?

[John_S]

Don,
I just read your reply and link to http://www.boatfix.com/merc/Bullet/99/99_10.pdf After reading, I think I have to exchange two gaskets. Please confirm.

I have a '97 Merc 5.7L with raw water cooling, and the 4 hose thermostat housing. Two of the four hoses enter the bottom of each exhaust manifold. I have 3" risers and the old gasket between the riser and elbow was a restricter. If I read the service bulletin correctly, I should use four of the 27-863726. These are the 4 slot and should go at the exhaust manifold to riser, and riser to elbow.

Two of the four gaskets I have, are the restricter ones, pn 27-863724. I was planing on installing the manifolds tomarrow morning. I might be waiting until Tuesday, if an exhange is neccessary.

 

[Don S]

Re: Don, Do I need to exchange exhaust gaskets?

If I read the service bulletin correctly, I should use four of the 27-863726. These are the 4 slot and should go at the exhaust manifold to riser, and riser to elbow.

Yes, you need 4 of the 726 gaskets.

 

[John_S]

Re: Don, Do I need to exchange exhaust gaskets?

Thanks Don. I'll have to wait until Tuesday. Do the elbows run cooler with the unrestricted gasket?

 

[John_S]

Re: Don, Do I need to exchange exhaust gaskets?

"Do the elbows run cooler with the unrestricted gasket?"

Answer to my own question: temp gauge same as before, elbows seem to run quite abit cooler. I am just running on muffs though, and maybe being impacted by colder well water. I did run the engine for 15-20 minutes at a time. Don't remember how warm they ran last spring on muffs. I did rutinely check while in the water. They use to get fairly warm. Not hot enough to have to remove hands, though. Will provide final update after first splash.

 

[Don S]

Re: Don, Do I need to exchange exhaust gaskets?

The reason for the restrictors in the gasket is to hold the water in the exhaust manifolds a little longer so the water has more time absorb heat from the exhaust. While it may make them feel a little warmer on muffs, it sure makes a big difference when out on the water under load...... That's where you need the heat transfer. Anything will work on muffs with no load.

 

[John_S]

Re: Don, Do I need to exchange exhaust gaskets?

So, the exhaust manifold and riser should be running hotter than before? Water would be circulating faster through them. The elbows, since they are getting more water flow, are probably running cooler. I assume Merc did allot of testing that said the unristricted were better per service bulliten?

 

[Don S]

Re: Don, Do I need to exchange exhaust gaskets?

I may have mixed up what I said with what you have.
Put it together like the SB says and it will be right and work like it's supposed to.