Initially runs good then bogs out after 20 minutes

[Nicksmind]

Hello everyone. Wish my first post was a better one and Thank you in advance for your assistance.

I am new to the forum and SeaDoo. I just purchased a 2001 Challenger 1800 with the Mercury 240 efi. I purchased this boat a couple weeks ago and my first run on the water was great until I shut it off and then it wouldn't start back up till it cooled for a half hour or so. Once it did fire back up it ran good for another 10 minutes and then started bogging out a bit at full throttle then three quarter and then at half. I took it home and started testing stuff. I hooked it up to the hose and after a few minutes you couldn't see the neighbors house from all the smoke.

Just another tid bit of info the boat sat for two years and a couple weeks before I purchased it the owner had $3200 of work done to completely revamp the fuel system. Based on looking at the receipt it looks like all the pumps, filters and everything was changed out to bring the boat back to running order.

Well I went through and changed the air temp and head temp sensor and adjusted the tps. Took it back out on the water and it smoked a little bit, but not near what it was on the hose. It ran out of the hole great right up to 55 and after kicking around about 20 minutes at half throttle it started to slightly surge at cruising speed. A few minutes later going to full throttle it started bogging down, then at 3/4, then anything above half throttle it bogged. all this happened within 5 minutes back to the dock. When back at the dock I shut it off and it did fire back up, but seemed to be smoking a lot more again. I took it home and did a compression test. all plugs looked ok, and all cylinders tested 108-110.

Any ideas if it might be a vapor thing, tps going bad, or something else. I checked fuel flow on the hose and it seemed ok, but not sure if it things settle and after running a while it clogs.

Also has anyone checked to see if you could retrofit mercury tps indicator 804298t to work on our motors?

Thanks again.

 

[Dr Honda]

What you are describing is an overheating issue.

First... it's almost impossible to run the Merc engines on a hose. The majority of the water will go out the pump. So... unless you have a big hose, and good volume... it will over heat. (Just a warning on that one)

Second... have you checked the buzzer, and temp sender?


The Merc engines do smoke... especially when not loaded. (ie, out of the water) And... they will smoke when first started in the water. So... what you are describing is normal. BUT... you can check the link going to the pump, and make sure it's set proper.

Lastly... bogging a 2-stroke is EXTREMLY bad. Since the oil is transported into the engine via the fuel... running lean is a death blow. Because of that... I would start with a compression check. (Cold engine, and open throttle) You are looking for 125~135 psi.

 

[Ken Inman]

Have you checked spark on all cylinders when this happens. Could be a trigger or switchbox breaking down under heat.

 

[Nicksmind]

I haven't checked spark yet when warm, but when cold at idle on the hose it doesn't seem to change on any cylinder when pulling the plug wires. idle seemed a little rough before I adjusted the tps. I had changed the temp sensors and the motor was cool to the touch when I was looking it over after it shut down the first time. I know the sensor and the buzzer works. I'm thinking the tps is intermittently working or one of the new fuel pumps they replaced is the issue. I really don't want to have to replace the tps.

 

[Nicksmind]

now I think I've figured it out. I'm pretty sure its a problem with the TPS indicator. I'm going to start a new post to see if anyone has tried an alternative as I couldn't find any post that confirmed an alternative used.

 

[Dr Honda]

I spent a year looking for a replacement. The issue is... the TPS used is a 10k unit. That's very unusual. Normally they are 6k or less. There is physically the same. It was for a Jag. But it's the wrong value. I was thinking about making a digital replacement... but the time and effort wouldn't have been worth it for the few engines that are still out there.

But... unfortunately... the replacement is $500. (just friggen ridiculous) If you dig around ebay... you may find a good used one. Also... there was one with a round plug that can be used. Just have to solder on your connector.