4.3 TKS Shutting Down After Warmup

[Kdubsc]

I have a 2005 Mariah SX18 with a 4.3 TKS. I don't have the serial number handy, but the engine is a 2004 manufacture. I purchased the boat this summer and had all bellows and the lower shift cable replaced, along with impeller. Also had trim senders replaced. Everything was Quicksilver straight from a dealer, with work done by an independent shop. Now to the symptoms.

The boat fires up and runs fine on muffs and in the water initially. After idling out to open water, she runs great until things warm up. Maybe 10 minutes in, she occasionally stumbles, sometimes to the point of shutting off and dieseling until the alarm sounds. She immediately fires back up with no hesitation. This can occur just a few times, or a dozen times, and is sometimes triggered when adjusting trim. However, if we go dock up at a restaurant and dine for 30 minutes or so, she fires up and the issue never presents itself again the rest of the day.

I can't say for certain that this all started after the maintenance that was done. Prior to that, I had only been on her twice, once for the test drive and once more for a few hours in which we never had these issues. Some things I've done have included cleaning battery connections and making sure they're tight, cleaned cannon plug (wasn't dirty), tested battery (brand new deep cycle with 600+ cca), removed trim pump assembly to clean and replace with 10W30, and a not very thorough inspection of other wiring thus far.

The trim operates normally, as best I can tell. It does drop the dash voltage from 14+ down to 12 or so when operated under way. Confusing part is that the shut down happens sometimes on its own, and also sometimes at my command via trim adjustment. Doubly confusing is that the problem always resolves itself and never reappears until we put her back in at the ramp another day.

Any ideas? I've researched the heck out of every available post on here. I do intend to do a thorough inspection and cleaning of wiring. Wishful thinking was a bad battery, but that tested out. Coil comes to mind, but seems once it got hot, it wouldn't stop causing issues over the course of the day.

 

[Kdubsc]

I wanted to add that even though it's a deep cycle and not a starting battery, it restarts the engine without effort every time. And on some occasions, a dozen times before the problems dissappear. So seems the battery is good and that the alternator is supplying enough to charge. Still seems like an electrical issue to me. Maybe not caused by trim pump operation, but surely exacerbated by it.

 

[alldodge]

Sounds like the carb needs work. Dieseling is caused by incorrect timing, running rich, idle to high or running hot

After the motor warms up see if the TKS plunger has fully extended

TKS plunger measurements
Cold = 20.6 mm to 22.2 mm (13/16 in to 7/8 in)
Warm = approximately 31.75 mm (1 1/4 in)

 

[Kdubsc]

Sounds like the carb needs work. Dieseling is caused by incorrect timing, running rich, idle to high or running hot

After the motor warms up see if the TKS plunger has fully extended

TKS plunger measurements
Cold = 20.6 mm to 22.2 mm (13/16 in to 7/8 in)
Warm = approximately 31.75 mm (1 1/4 in)

I'll check that out. Still mysterious that it works itself out over a trip. She runs around 160 to 170 on the temp gauge as well.

 

[Kdubsc]

Sounds like the carb needs work. Dieseling is caused by incorrect timing, running rich, idle to high or running hot

After the motor warms up see if the TKS plunger has fully extended

TKS plunger measurements
Cold = 20.6 mm to 22.2 mm (13/16 in to 7/8 in)
Warm = approximately 31.75 mm (1 1/4 in)

Also, not that the tachometer is 100% accurate, I noticed she idles at 500 rpm when warmed up. Seemed to stay the same in gear and out. I believe the labeling on top of the flame arrestor calls for 650 rpm. Not that I'd think that would cause me to lose power and diesel while running 3,000 when trimming. Wishing I got the old center console I was looking at now.

 

[Kdubsc]

Going to trailer boat home this evening to play around with it. I'll add that I think the TKS is working properly. It has the hissing noise as we idle out to open water. This eventually goes away, which I assume is the plunger doing what it was designed to do.

 

[alldodge]

Timing should be 10 BTDC set in base timing mode.
Plugs MR43LTS gap at .045

 

[Tassie 1]

To me the stalling etc etc at idle/ low rpms sounds a lot like a problem l had with a 5.7 MPI a few years ago.

i don't know whether the system in question has the Idle Air Control. ( not going through 658 pages in the manual ) but if it has l would do some research into that,

l may well be wrong though.

 

[Kdubsc]

To me the stalling etc etc at idle/ low rpms sounds a lot like a problem l had with a 5.7 MPI a few years ago.

i don't know whether the system in question has the Idle Air Control. ( not going through 658 pages in the manual ) but if it has l would do some research into that,

l may well be wrong though.

Reading my original post I guess I didn't come across clear enough. It idles fine, although at a lower RPM than recommended. Its while running 3,000 or so RPM that she dies on me. She planes off great and after maybe 5 minutes will start the routine. Stumbles, starts shutting down and diesels. Sometimes she will calm down if I quickly reduce throttle. This happens on its own, but also when trim. Starts right up no problem, with no cooling down period. It occurs numerous times. If we dock her and go grab a bite to eat at a restaurant, she fires right back up and never gives an issue the rest of the day.

Occurred yesterday, and we were a half mile into what is probably a 6 mile ride across the lake. Did it over and over to the point I was going to turn back. After lunch, we drove the entire 6 miles without any hesitations. Seems if it was a heat issue it would continue to present itself as the day gets hotter.

 

[Kdubsc]

I haven't found much in the way of corrosion while checking wiring. I did polish the all battery cables to a shine and tighten them good, although none were really that dirty. Also pulled the distributor cap and noted that it was original to the engine. Screws still had paint caked in the heads. Inside was even marked 11/14/2004 in marker. The contacts inside the cap had some junk on them, so I lightly sanded it away. May replace the cap if I go with a tuneup, either now or when winter hits. Haven't pulled any spark plugs yet, but will this week. Plug wires look new, although everything in the 15 year old boat is that way.

 

[Kdubsc]

One last thing for the night. At cold start, she ran about 1,000 RPM on muffs. Could clearly hear the TKS plunger allowing air in. After warming up, the rush of air ceased and she settled down to 500 RPM. I know idle is supposed to be set in the water, but the idle RPM was 500 in water as well after warmup. Also sprayed a little carb cleaner in carb. Didnt look too dirty from above, but who knows how it is inside. I'd suspect it has never had work, but the screws seemed marred as if someone had cracked it open before. I'll probably look at a rebuild this fall.

 

[Kdubsc]

Pulled one plug for inspection. It doesn't appear too bad, but what do the experts think? Also, its a 41-932, which appears to have been replaced by 41-933 some time ago. I'm guessing these are original, or have been in there a while. Any issue going with the MR43LTS? I read elsewhere that the plug currently in it contributes to dieseling. Not sure how true that is, but worth a shot.

Edit: Info on arrestor actually dictates MR43LTS. Guess I have the "wrong" in it currently. Will switch to what they recommend. Maybe it has had a tuneup at some point after all.

 

[Kdubsc]

Also got a look at the plug wires. Still have the Mercruiser part tag on them and they are original 2004 wires. I planned to replace along with plugs, but a tuneup definitely appears in order.

 

[alldodge]

Your running rich and the plugs would clean right up on their own if the mix is leaned out.

Yes the 932 took the place of 933, and LTS are the plugs called out in the manual. The MPI manual call out the 932

 

[Kdubsc]

Your running rich and the plugs would clean right up on their own if the mix is leaned out.

Yes the 932 took the place of 933, and LTS are the plugs called out in the manual. The MPI manual call out the 932

Ignorant question. Is a rebuild the only option to clear up the mixture? Its probably due for one, but Ive never done a rebuild. Not afraid to take my time and order the proper kit, but if there is anything else to adjust in the meantime I'd try it. Still considering the plug change. I probably need a new cap as well. I used very light sandpaper to remove deposits on the inside. I should've taken a pic, but each contact had a fair amount of buildup.

 

[alldodge]

Running rich for a carb motor is only controlled by the carb
Things that can change it is if the main jets were changed. Most would not change the jet but they might find one for another motor and install it on yours. Can also be by float level to high or float sinking

 

[Kdubsc]

Running rich for a carb motor is only controlled by the carb
Things that can change it is if the main jets were changed. Most would not change the jet but they might find one for another motor and install it on yours. Can also be by float level to high or float sinking

Picking up a Sierra carb kit today. Dealer didn't have Quicksilver kit. Never done this before, but willing to try if that may help. I'm also curious to see inside the carb and clean it, which requires the gaskets anyways. Any advice besides dont screw it up?

Also, seems like a trace of gas is able to wick through the gasket in front. Not much, but any is obviously not ideal. Another reason to at least take her apart.

 

[alldodge]

Use fishing line or a then wire to clean out the small passages, and follow the manual so far as settings

http://boatinfo.no/lib/mercruiser/manuals/mercruiser41.html#/0

 

[Kdubsc]

Got carb apart. Not at all dirty. Seems it was serviced not long ago. Wouldn't expect it so clean after 15+ years. Float level was a bit off and I adjusted it per specs. We shall see how she runs with the new plugs and carb work.

 

[Kdubsc]

By no means spotless, but I expected worse.