Been troubleshooting an issue on my ski, it was bogging down, running very rough, and top speed would surge. I eventually pulled the plugs, found the center cylinder spark plug was melted and after a compression test, discovered 0 compression on that cylinder(other two were at 170). I'm trying to figure out what first off would cause something like this since I've been told these engines are pretty solid(part of why I didn't get the 230/300). Second off, what are my options? I've rebuild car engines, but no experience with PWCs. Pretty bummed right now. Engine has 106 hours.
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2020 GTX 170 with 0 compression on #2
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Milehighguy303
Active Member
It does seem very confusing and the engines are generally very reliable. I wish I had a good answer. I think the fuel injector may have failed and run lean and increased heat in the cylinder? Not sure… With no compression, you likely have valve damage too. I can’t imagine your piston rings and cylinder wall being damaged severely, but hard to know. Unfortunately you need to pull this engine and tear down completely to inspect the valves and cylinder.
mkov608
Active Member
I feel your pain! My 2017 GTR (58 hours) melted a piston on cylinder 1 last fall. I rebuilt the engine, new block $1,700.00 big ones, 1 new piston, all new bearings, all new rings, and lets not forget the crazy amount of o-rings and seals. I also replaced the #1 cylinder fuel injector, and the CTS. The cylinder head had to go to the local machine shop because melted parts of the piston damaged the valves and valve seats. Everybody that I discussed the damage with went right to a lean mixture in that cylinder. I took the #1 and #2 cylinder injectors to Pensacola, Fuel Injection for a bench test and flow comparison. They said the #1 injector flow rate was identical to the #2 at 5 different pressures, but suggested it may have been a temporary clog/restriction that cleared out.
The reason I changed the coolant temp sensor is from what I read in the service manual. Sea-Doo engine computers run the engine lean when they are cold so the engine reaches operating temperature faster. So, that made me wonder ... what would happen if the CTS failed in the "Cold" state? In theory, the ECU would continue to lean out the fuel/air mixture because it thinks the engine is still cold. I pulled my CTS, and measured the resistance at different temps, and the numbers were not in line with the service manual. So, I changed it. My first trip to the boat ramp, I connected my CanDoo Pro to the ski and monitored engine temp. It hit 195F.
The owner's manual says you can run 87 octane gas in my ski, but the majority on the forum say you shouldn't'; so I pumped all the gas out of my tank and refilled it with 93 octane ethanol free gas before I fired up the rebuilt engine.
She's back together now and running well. Total cost was about $4K for parts and special tools. The most expensive tool was the jet pump/engine alignment tool.
The reason I changed the coolant temp sensor is from what I read in the service manual. Sea-Doo engine computers run the engine lean when they are cold so the engine reaches operating temperature faster. So, that made me wonder ... what would happen if the CTS failed in the "Cold" state? In theory, the ECU would continue to lean out the fuel/air mixture because it thinks the engine is still cold. I pulled my CTS, and measured the resistance at different temps, and the numbers were not in line with the service manual. So, I changed it. My first trip to the boat ramp, I connected my CanDoo Pro to the ski and monitored engine temp. It hit 195F.
The owner's manual says you can run 87 octane gas in my ski, but the majority on the forum say you shouldn't'; so I pumped all the gas out of my tank and refilled it with 93 octane ethanol free gas before I fired up the rebuilt engine.
She's back together now and running well. Total cost was about $4K for parts and special tools. The most expensive tool was the jet pump/engine alignment tool.
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