2000 Tige 20i - Heavy carbon on spark plugs, hesitation

[jgdethloff]

Good news on the injectors!

Just some input on the ECT: I did test the resistance of the ECT with the engine cold (the ECT at ambient air temperature.) The resistance in OHMS was exactly what it should be to with the corresponding outside air temperature.

Regarding the ECT test: are you are searching for why I have carboned up plugs, and hesitation with this test? So if I take the boat out today (with the reduced oil level) and everything runs fine, then is there any concern regarding the ECT? OR does a failing ECT = the low fuel pressure at the fuel rail? OR did we determine that the fuel pump is on its way out by the fact that the injectors are good and not leaking?

Thank you!

[boatwakes]

At this point the fuel pump would not be a focus point but rather an eyebrow raiser. Something to consider, and I'll have to dig out the manual to get the values, is the ect may never show the correct resistance near correct operating temps. Again, it has to show the ECM 140* in order for the pulse width to narrow to operating parameters. The carbon build up, black smoke and hesitation are pointing to overfueling which is controlled by a few things with the ect and mat being the foremost in regards to injector pulse width.
Where are you located?

[jgdethloff]

Thanks Boatwakes,

I went ahead and ordered a new ECT - for $25 it is easier just to be sure. Is there any difference in a MAT that I can pick up at Autozone for a GM car/truck motor and a MAT by Quicksilver/Mercruiser? I can pick one of those up for $20 instead of $60 for the Quicksilver part.

I live in Jacksonville, FL

[boatwakes]

Nice! No difference! What's the part number?

[jgdethloff]

So I went to NAPA and bought new: ECT, MAP, MAT and installed them. I also put in new NGK plugs. Went out on the river for a test this afternoon and same thing- rich, rich, rich...

BUT, I have an answer. The temp guage worked fine on my sea trial- Right around 175. When the hesitation started, the temp guage was not registering. Actually, it would register every once in a while and then go back to the bottom. I thought it was either the sending unit or a loose wire on the guage... I replace the sending unit today AND made sure the wires were tight... it did the SAME THING- at the dock, it showed that it was warming up. But once I got underway the temp went back down very low! When I would come off plane and idle, the temp would go up to 175 then right back down to very low. Very inconsistent- I'm betting the thermostat is bad- THUS the ECT is reading low temps and making the boat run super rich like it would when warming up!

If you think it might be something else, let me know- otherwise, back to NAPA!

[jgdethloff]

New thermostat today. New gaskets with it. The only thing I didn't replace is the plastic sleeve. The local boat shop didn't have it in stock. There is a small "tit" on the plastic sleeve that broke off when removing it, however, I don't believe this affects anything. The temp gauge appears to be held in place firmly. I checked that the gauge I remove AND the new gauge are oriented correctly. The temp gauge is STILL fluctuating up and down.

When I a under power, it tends to show no reading. When I back off power, the temp gauge comes up to 175 and then back down. I can, in neutral, give it gas and then back off and it makes the temp gauge go up and then back down. When you grab hold of the hose that goes to the exhaust manifold, you can feel water flowing out suddenly when the temp gauge goes down.

When you shut the motor off and then turn the key to "on" it registers temperature consistently! What do you think is going on???

[jgdethloff]

WNYTige had a thread that says he had the same broken "tit" off the plastic sleeve and when he replaced the sleeve with a new one with the "tit" the temperature fluctuations went away! At this point I am uncertain if I broke the piece or it was like that when I pulled it out. I'm ordering a new one and will report back unless someone has a better suggestion!!

[jgdethloff]

I found a local store that had the sleeve. While I was there, I picked up a water pump because I read in another forum someone had a bad water pump and their boat had the same symptoms. When I got back to the lake, I replaced the thermostat sleeve. Boat still fluctuated in temperature.

I pulled the water pump and then pulled the impeller cover off the back of the water pump. THE IMPELLER WAS CRACKED IN HALF!! Replaced the water pump and all is good!

[WYTige?]

That is good new!! Been following this and hoping you would find a solution. Well done!

[TeamAllen]

Good work. Glad you found it and updated the post for others.

[boatwakes]

Holy crap!!! Nice detective work and that is something I wasn't expecting. Right on!

[Ewok]

Nice work! I guess it's a good example as well that if you're doing general tune up work and it a new to you (used) boat and you're not sure on the condition of the impeller it's a good idea to change it out.

[jgdethloff]

Here are a couple pictures of the old water pumpIMG_7352.jpgIMG_7353.jpg

[boatwakes]

Thats even more bizarre, thats the circulating water pump!!!! WOW!