1985 Mercury 200hp WaterProblems #2

[jbcc2500]

I have replace water pump, impeller, poppit valves and removed T-stats. Disconnected water lines at the heads and water will shoot out 3 foot. When I reconnect these it only spits out of the telltale. I have jammed wire and weed eater cord up into it but now luck. It only goes in about 2 inches then I cant push it in any further. Also when I put it in gear it stops spitting and only steam comes out. WTF?

 

[CharlieB]

Re: 1985 Mercury 200hp WaterProblems #2

You may have two seperate problems.

First, there may be something stuck inside the P hose limiting flow. Remove the hose and clear it.

Second, steam from P hose while in gear. Is this with the boat in the water or while on the trailer on the garden hose? Reason being, in the water there is LOAD placed on the motor which causes cylinder pressure to raise greatly then idle or RPM in either Neutral or unloaded on the garden hose.

Steam from the P hose is often an indication of a leaking head gasket, combustion gasses blowing into the cooling system displacing the water and rapidly overheating the motor.

Do NOT operate the boat without test to determine the problem and repair.

A compression test may show a difference in cyl pressure if the leak is bad. However a small leak may not be evident with a simple compression test, a cyl leak down test is a bit better but still limited in pressure.

It may be necessary to bite the bullet and invest in new headgaskets, to be SURE.

 

[jbcc2500]

Re: 1985 Mercury 200hp WaterProblems #2

All hoses, valves, elbows, everything is clear. It has to be something internal. When the steam comes out, the boat is in the water and in gear. When its in the water and in neutral it spits out of the pee hole. How much does it usually cost for compression test and replacing a head gasket. Sounds pricey.

p.s. I havent seen any water on the spark plugs, dont know if that means anything. They are always wet with gas

 

[CharlieB]

Re: 1985 Mercury 200hp WaterProblems #2

Compression tester, spark plug wrench, and either a helper or a remote starter button to crank the motor.

All available at your local auto parts store, Sears, etc. (except for the helper).w

Pull the Lanyard to kill the ignition.

Remove the spark plugs, screw in the compression tester, crank the motor over til the guage stops climbing (about 5 or 6 turns), write down the reading. Repeat on all cyls.

Head gaskets aren't to bad, under 100, very cheap when compared to a 3000 rebuild for an overheat! You can download your service manual from links found in the 'sticky' at the top of the forum, and do the job yourself. Headgaskets are one of the easier jobs. But TEST first! Repost your findings.