Cooling water question

[natecollins1]

I was working on a 4.3L Mercuiser w/ Alpha 1 Drive. The engine gauge is showing 160, but some steam is coming out of the exhaust water discharge. I used a temp gun and the front two cylinders are showing about 205-220 degrees. The thermostat is reading about 160 F. I changed the water pump impeller and made sure I realigned the water tube properly. I am still showing the same conditions with the new impeller. I checked compression in the #1 and #5 cylinder. They are showing 100 psi and 123 psi respectively. I also pulled the fresh water inlet hose to see how much water the lower unit was pumping in to the engine. At idle speed, if you look at the end of the hose you see that there is enough water to fill about half of the diameter of the water hose (hose is about 1-1/2 to 2" in diameter) and it flows at about the rate of a garden hose with a valve 1/2 - 3/4 of the way open.

Do you think that I have enough water flow to the engine?
Do you think I may have a scoring issue related to the piston(s) that may be causing the front of the engine to be running hot and steam to be generated?
Any other suggestions would be great.

 

[tractoman]

Re: Cooling water question

Did the plug in #1 look like it's been steam cleaned. 23lbs is a big variance in compression, and I am wondering if there is water entering the cylinder in #1making the steam? I am guessing you are on a trailer when you see the steam?

 

[natecollins1]

Re: Cooling water question

No the spark plug in #1 looked dry and pretty normal. I did not see any signs that is was "steam cleaned" or had any errosion/corrosion.

 

[zbnutcase]

Re: Cooling water question

Depending on climatic conditions, some steam is perfectly normal!

 

[natecollins1]

Re: Cooling water question

After the boat has run for about 20 minutes it starts running rough. You can tell that the engine rpm drops down to about 500-550 rpm and the owner says that it was running rough for him at high speed. There does not seem to be any fuel or ignition problems, I just notice that the front of the engine is definitely too hot (normally I am reading about 160-180 F on my temp gun around the exhaust ports of the engine block). I am seeing a lot more steam than is normal at the discharge water ports of the transom bracket.

Does anyone know roughly how much water should be flowing from the water inlet hose at idle? This will help to eliminate a water flow problem since I am getting some water, but don't know if it is enough.