Inline 6 question.

[DanOG]

I have an 84' Inline 90 and I noticed today while running on the hose ALOT of milky Sut leaking out from prop. I first thought it was the lower Crank seal leaking gas/oil but then pulled the lower unit to see it was comming from inside the megaphone... Could this be comming from the adaptar plate or from the exhaust chest? Or both? It seems to be running great. Is this something that requires immediate attention? Or could I get away with using it for a fishing trip for a week? What do you guys think? Any help would be appreciated. Thanks!

[Superdave]

Your inner water jacket cover is leaking or cracked. I wouldn't recommend running it at all. You will get water in the cylinders and score pistons. Not good. Pull your spark plugs and do a compression test first.
Dave

[wrechin2]

I think superdave has hit it right on the head! Inner water jacket cover or gasket leaking. These are noted for this.

[Raceman]

The inner plates have been known to leak on inlines. Have you looked at the plugs for signs of water?

[DanOG]

Oh great, looks like a fun job to do. I haven't checked the plugs or comp. yet but I will in the morning. It looks like either way the powerhead has to come off... I just hope I can rectify the problem before my fishing trip Mon. Thanks for the speedy replies and the good advice! Dan

[Jeff_G]

Firdt look at the plugs for any sign of water, but... The water dumps with the exhaust under the powerhead anyway so the milky stuff would not necessarily point to a leaking plate. Even with a properly running motor you can build us some milky gunk around the driveshaft which will leak down the mid section.
It actually sounds more like you have either a overly rich condition or a cylinder not firing. This would lead to a lot of unburnt gas mixing with the exhaust water. Something you would notice on the hose and not while running.
1. Check plugs for water
2. Check for proper firing of all cylinders
3. Check the idle adjustment on the carbs, check the plugs for overly wet condition.
Could be nothing more than a rich carb or bad coil.

BTW a compression test will not point to a leaking inner plate. There is no good test for water leaking from the plates.

[DanOG]

The water jacket gasket was the culprit. I checked the plugs and found signs of moisture... So, I removed the power-head and pulled the exhaust cover to find lots of milk in the exhaust cavity. I replaced all the exhaust gaskets, adaptor gaskets, and even threw some new mounts in. Thanks to you guys looks like I'll have a long and prosperous fishing trip in god's country Thanks again!!! Dan

[Jeff_G]

Did you replace the inner water cover? Or just the gasket?

[sosmerc]

I'll bet I know where you are going with this Jeff!
Those inner plates cause lots of problems. I finally learned to have both the plate and the block resurfaced before installing. I even have the plate done if it's brand new. You also have to resurface the block where the divider rests by the same amount that was removed from the inner surface...so that the divider rests down properly on the inner plate. Then you need to use the resiweld sealer on the bolts. It's alot of work, but it does solve the problem. I replace the lower end cap seals as well....and since the block goes to the machinist this work is usually part of a minor overhaul at the least....new rings, seals and gaskets, etc.
Those inner water jackets are quite a pain indeed.....I always thought it would be cool if Merc would build the inline six with cast in exhaust and block covers such as they do with the newer 3 cylinders such as the 50hp.