Next step--- took the boat out today....

[93nitro]

Ok got the decarbing done last night. Changed the fuel filter and rechecked compression and seem to have less compression now than I did before the recarb. Top 100, center 100 and lower 60psi. Whats going on??? When I took it out the motor fired right up and idled great. Let it run for about 5 minutes to warm up. Hit the throttle and it died. Restart and took off slowly. When I tried to get on it, it died again just as before. I could still feather it and get it to WOT. After doing this it idled terrible and did the rest of the time I had it running. I am lost on this motor now. Please help.

 

[Frank Acampora]

Re: Next step--- took the boat out today....

Although my opinion may be unpopular with some people on the forum, there is a reason I do not like seafoam and do not decarb my engines with it or any other treatment, and do not add these "snake oils" to my gas either: It is NOT uncommon for engines to show worse compression and performance after a decarb treatment. In fact, somtimes the treatment will cause significant damage.

However, There are circumstances where I would recommend it as a last resort before going on to more expensive repairs

You can try squirting a couple of ounces of straight TCW-3 in the carbs while the engine is at high idle and see if this brings up the compression numbers a bit.

 

[steveclv]

Re: Next step--- took the boat out today....

I am in agreement with Frank - in 95% of cases, these engines do not need decarbonizing andas you found, you can lose compression because of it. The only time I have ever found the need to decarbonize an engine is when I was getting preiginition and that was in 1974 before the oil quality was anything like as good as it is today. The carbon that builds up around the rings and pistons helps to seal them and removing it reveals the wear in the rings, ovality in the bore etc that was hidden by the carbon deposits.

The very nature of an oil burning engine means that it will build up a layer of carbon - that in itself is not a bad thing. Only when it gets excessive is it a problem and with modern oils that is far from likely.

Having said that, I doubt that the low compression is causing your problem. What else have you done so far to the engine? Have you replaced the fuel pump diaphragm, checked the fuel pick-up strainer, checked the timing at WOT, checked the idle mixture?

If there are other threads pertaining to this it's a good idea to keep the original thread going so that we can see what else was tried.

 

[jerryjerry05]

Re: Next step--- took the boat out today....

Do another compression test.Low compression will cause poor performance.You need all 3 cylinders to operate right.
Still bad compression? Remove the head.Check for a bad head gasket or a damaged cylinder.
No amount of repairs you do will make it run right if the compression is off and a difference of 40# is OFF!
The only time I add anything to my gas is if the boats gonna set for a long time. Fortunatly it doesn't set.
I use Power Tune about once a year,maybe more if I use it a lot.
Are the plugs all firing good?Any water or milky oil on the plugs?That's a sign of a bad head gasket.J