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1999 Sea Ray 454 Mag MPI Blew My MotorHELP

T

Thomas Dahn

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"I have a 1999 Sea Ray 280BR w

"I have a 1999 Sea Ray 280BR with a 454 Mag MPI 385HP and the Temp warning would come on when at high RPM (220deg)I would then slow it down to idle and temp would fall to 170deg. Well, this happened about 5 times, and then the starboard side PCV valve on top of the Valve Cover blew off and a mixture of Water and Oil started erupting out of the PCV hole in the valve cover. I immediately turned the motor off and have not tried to start it yet. This happened today and I got a tow back to the ramp. Where should I begin? I want to do this work myself. I am immediately thinking blown Head Gasket. Any help from anyone would be much appreciated. This was my first day out in the boat and my wife is ready to slit my throat. HELP!!!"
 
"shut off water supply. remove

"shut off water supply. remove spark plugs. spin engine to remove water from cylinders. get wet oil out of there. shoot a little oil into cylinders to preserve.(oil can) fresh oil and a compression test for a start. remove water pump belt to preserve pump, impeller should be replaced but pump body is plastic. wife is right to be upset (5 times?) after the first or second overheat You should know You have a problem. they seldom heal themselves. buy Her a nice dinner and good luck."
 
"Problem turned out to be the

"Problem turned out to be the intake manifold. The Aluminum Intake Manifold has an area on the back of it where the cooling jackets come up and the manifold blocks them off. But there is salt water hitting the manifold directly in these areas. Electrolisys had literally eaten the manifold away and the cooling jackets blew out into the oil valley below the intake manifold. Once this happened, the raw water pump proceeded to completely fill the crank case with water to the point that it was blowing out of the top of the valve covers. Nothing anyone could do about this one. Just a poor design flaw be Mercruiser. I ended up pulling the motor and completely rebuilt it from the ground up. And, I powder coated the intake manifold on both sides.
Thanks Guys."
 
"Hi: My husband bought a Sea R

"Hi: My husband bought a Sea Ray 1998 370ac with mercruiser 454 engines with only 300 hrs. The RPM on one engine would drop off after a short time. We are now being told that a similar problem has destroyed the engines and we need to replace them both for $40,000! The boat is now in pieces in Lodi California. They are also telling him that rebuilts will have the same design flaw and to go with 8.1 Horizon @370HP. Diesel was quoted at 60k! Any thoughts before my husband needs CPR? Did Mercruiser issue a recall or give compensation for what is clearly a design flaw on their part? Thanks"
 
"Only in California could they

"Only in California could they get 40K to install two gas engines.

Just like the result of this original post, you don't always know what you are going to find. Most likely something else has changed over time which caused this failure. It did not run for eight years with this "flaw". I don't know the history of your boat, but if certain items, such as manifolds and risers are not maintained on a regular basis, you will get this result. Yes the 8.1 is a better system, but you should be able to have a pair of new 7.4 longblocks along with new exhaust systems installed for about half of the 40K you were quoted for new motors.

Done right amd maintained properly, they should last a lot longer than the eight years you got out of the first pair.

Good luck
Rick"
 
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