[Kromrider]

I recently bought a 19 foot boat powered by a 1975 135 HP engine. At first the engine ran fine although it was a little hard to start. After about 20 minutes the engine started to loose power and we limped back to the dock and brought the boat home. We pulled the plugs and all four plugs were fouled. we changed the plugs and took it out a second time and had the same results ran okay at first but then lost power and we limped back to the dock. again all four plugs were fouled. I checked over the wiring and everything seems to be clean and tight. I am thinking it may be some type of ignition problem or loose wires as the problem the second time out started after we crossed some wakes (bumped). Any suggestiions?

[ezeke]

Using a 50:1 87 or 89 octane fuel to TC-W3 oil that is a synthetic or synthetic blend will help. BRP XD-50 has a built in carbon treatment called Carb-X that will help you to keep the system clean; synthetic oils have a higher flash point.

First, do the de-carbon treatment to clean up your engine because if the plugs are fouled, so are the rest of the firing chambers: http://forums.iboats.com/showthread.php?t=158076

Make sure that your thermostat is working, because nothing fouls quicker than a cold engine in my experience.

If you don't use the Champion UL77V plug, I would highly recommend that you use Champion QL77JC4 gapped at .04 until you get back to us with your compression readings.

[Kromrider]

Okay i spent all day Sat working on the boat. Seafoamed the engine both ways. Did a compression test on the motor and all four cylinder were within 5 pounds of 150. I used the fuel cell I bought to rule out any gas tank issues. I got 6 gallons of fresh gas mixed with TC-W3 synthetic oil. I changed the plugs and headed to the lake for a test ride. Engine started right up and we did a full throttle run accross the lake with no problems. We stoped to put out the tube and had a little trouble restarting the engine. I tried to go and the engine would stall as soon as we increased the throttle. we were able to restart the motor and limped it back to the dock. any time we tried to increase the rpms it would stall. all four plugs were fouled and I a convinced it is some kind of ignition problem. Any suggestions?

[ezeke]

Have you had the thermostat changed?

Look on the top of the engine block, next to the lifting eye, and see if there are wires running from there to the terminal block.

Also see how many wires are running from the choke solenoid to the terminal block.

The four coils on the the rack at the top are subjected to a lot of heat and are a frequent problem. They can function normally when cold and break down when warm. If they are discolored, cracked, swollen or melted, it would be good to replace them. The newer replacements are better.