1993 Mercury Quick silver 90 hp

[harley98]

I recently took my boat to a dealer for service and they replaced the water pump in the foot. Plus while the other old one let go my engine over heated a little and they had to replace the head gasket. Now there is about 20lbs difference between the compression in the first and third cylinders. The first reads about 147, and second 136 than the third reads 127 about. I was told that it wasn't to good and might not last. Is this true and is there anything i can do to fix this ? What options do i have ? The engine only has about 50 hours on it. They cleaned all three carbs also.

 

[Laddies]

Re: 1993 Mercury Quick silver 90 hp

It sounds like the overheated I think that the rings may be sticking get some Powertune at your merc dealer and spray the cyls and let it set over niite and retest it then run it and fog it thru the carbs like it say on the can let it set overnight again run it, recheck compression and it should be alright

 

[Silvertip]

Re: 1993 Mercury Quick silver 90 hp

I can't believe at 50 hours the engine is carboned up so much that compression is affected. How long did you run it after the overheat? Did the engine die and then restart after it cooled? My feeling based on your limited info is that you did hurt the engine. How badly will be determined in the near future. You can continue to use the engine for another 5 hours or so and repeat the compression test. If its worse, you can prevent its total destruction by tearing it down and rebulding itl

 

[harley98]

Re: 1993 Mercury Quick silver 90 hp

I bought this boat from an old man that had it parked for a number of years and than i used it for about 2 summers until the pump let go and all this happened. I also had it parked for about 1 year. The engine didn't stall out or anything. I noticed that the pump had let go while i was out in the water and started going back to the dock when it started to loose power and blow some white smoke. I did make it back to the dock which took about 10 minutes and never went back out since. The only thing other mechanics did to it after was replace the head gasket and i parked it. I only decided to bring it to another dealer who i knew was more experienced in boats last week. They found other problems like badly tuned carbs and they also are replacing the water pump with a whole new kit. Also they found that it was taking in a little of its own exhaust dew to some sort of pipe that let go or was not properly installed at first on the inside. So they fixed all that so far. Everything seems ok now accept the low compression on one piston. I originally just thought that it was parked for so long before that old gas had it all gummed up everywhere so it really just needed cleaning and adjusting. It did i guess but now i'm scared the low compression is another whole ball game that just might be the end to this engine. Is 127,136 and 147 really that low or bad ? Or a difference of 20lbs of compression between the first and third ?

 

[Silvertip]

Re: 1993 Mercury Quick silver 90 hp

10% difference from low to high is considered ok. This is a tick over 15% difference. The engine may sound ok and even appear to run smooth but one cylinder that's down over 10% means the engine is not making full power and that something is wrong. Differences in reading technique, engine temp, when the test was done, crank time during the test, can all affect those numbers so I would use a different gauge and recheck on a warm engine. If the numbers are still the same, that cylinder has an issue. How long it will run one can only guess. Perhaps a long time. I would certainly use a pen light to look into the plug hole and see if there is any evidence of piston damage. And perhaps pull the exhaust cover to inspect the piston skirts for evidence of scoring.