mxz800

i second the intake gasket. had the same problem with my street car, would run fine cruisin around town. When you sprayed it down a couple of times started smokin and oil in water. seems runners were large enuff in the head that the gasket wasnt sealing with much and would give in under enuff of a load.

Rob

Vinny P

What bothers me here is the fact that it ran good for 18 hours. What if anything changed to cause this problem? I will guess that during the first 18 hours you beat on it enough to know that it was o.k. I am going to ask you a stupid question, you are not running that motor hard with that Captains Call dumping your exhaust through the prop are you???

syringa

Hey checkmate>> At this point there is no such thing as a stupid question. Believe me I tried running it with the captains call open or closed and you don't even have to pound on it for the problem to show up. Like I said prev. I ran it for a hour at 3500 no problem but as soon as i open it up to 4000 4500 the puke starts coming out of the breathers. Higher rpm takes about 3 min to contaminate the oil with water slower rpm (but over 3500 takes a bit longer. I'm stumped.

US1 Fountain

iTrader: (1)

Are you running a crossover and a bypass hose or the stock Merc T-stat housing with the tee for bypass and stock water recirc. pump? Do you have a water pressure gauge? If not, I highly recommend one. It sounds very much like intake gaskets leaking is a very high possibility. I assume during the 1st 18 hrs of break in, you babied it and didn't do any high rpm runs? Possibly with the 160 stat and the cold lake water temps, you are having trouble getting the stat to open enough to flow all the water. A stat starts to open at the stated number and then fully opens as temp gets higher.
Say your temp is fine at idle or even cruise, you aren't flowing max amount of water at this point. The stat is open enough to relieve the excess water. But once you open up the throttle, you are flowing more water. More of this cold lake water will actually close the stat some, now you have more restriction= high water pressure. This high pressure gets relieved by blowing past your intake gaskets and right into your oil. Try running a 5/8" or a 3/4" restrictor instead of the stat. Just make sure your water pressure doesn't go higher than 25psi. 18psi is really the disired number at WOT.
Been there done that. Speaking from 100% experience, not text book theory.
Good Luck,

Jerry

MitchStellin

I had the exact problem. I mean EXACT. The boat ran fine until wide open or above 4000rpm. It would miss and sputter. The Oil had water also. It is a leaky riser gasket. It is washing out the spark and you are dropping a cylinder. It will clean itself out and run but comes back. At slow speeds the water is not flowing hard but at speed it is sucking like mad. Fix both gaskets at once for sure.

syringa

Well maybe i'm getting somewhere. On the advise of US1 Fountain I ordered a water pressure gauge which wil arrive tomorrow. I took out the t stat and ran it at 3500 4500 and WOT . No miss and nothing coming out of the breathers but the oil is still milky even after 2 changes. I will change the intake gaskets next but want to know what the water pressure is first.
Thank you all for the replys and good advise

syringa