199 40HP 2 stroke Merc stalls at low idle

[Otis313]

Frustrating... that's the best word I can think of without using profanity.

I have a 99 2-stroke 40HP that has problems stalling at idle. If I move the idle lever up half way, it starts no problem at all.... warm or cold. When I reduce the idle speed to drop into gear is when it stalls .. If I reduce speed VERY slowly to idle, sometimes it does not stall. I end up having to drop the lever and shift really quickly into Fwd to RVS and add gas to keep it running. Causes some real headaches when docking or in tight spots.

Runs at WOT no issues, but if I decelerate quickly it will stall. Decelerating slowly before shifting to neutral usually stalls, but not always.

Hoping this may be something simple like idle RPM setting that needs to be bumped up a bit, but wondering if there could be more to investigate here?

Thoughts?

 

[Silvertip]

Re: 199 40HP 2 stroke Merc stalls at low idle

Have you mucked with the idle speed and idle mixture screws? Did this issue just come up? Is the boat new to you? Details - details - details.

 

[Otis313]

Re: 199 40HP 2 stroke Merc stalls at low idle

Have you mucked with the idle speed and idle mixture screws? Did this issue just come up? Is the boat new to you? Details - details - details.

The boat is relatively new to me... I bought it in the late fall of 2011 and used it a bit last year. There were some rough running issues with popping and coughing, in addition to stalling and the mechanic suggested it may be water in the gas tank. Boat is a 1999 Legend V178 with built in tank that was only half full when stored the previous winter so it made sense to address that before anything else. I ran 2 tanks of gas through it with a water remover additive while at the cottage last summer and it eliminated the popping and coughing but stalling at idle was still an issue. When I got the boat out again this summer, I added the water remover again and it took care of the popping and coughing again after the first tank but the idle stall issue was still there.

No, I have not yet adjusted the idle or mixture screws. Whats the best approach here to ensure they are set properly? Looking for stuff I can check myself before forking out cash and taking it to the mechanic .

Cheers... Jon

 

[Toddboat]

Re: 199 40HP 2 stroke Merc stalls at low idle

I would make sure the idle circuits in the carbs are clean as a whistle before playing around with the idle screws. A good carb cleaning, particularly after long storage, is a must. If that alone doesn't do the trick, then buy the manual and run through the link and sync procedure. It should tell you how to adjust idle speed... in the water!

 

[Polara Pat]

Re: 199 40HP 2 stroke Merc stalls at low idle

I'm having a similar issue with my '93 Merc 40 so I'll be watching this thread to see how you sort it out. The advice given so far seems really sound. You can download a manual then print off the sections that you need. The "link and sync" section is critical so start there. How do your plugs look? Mine are getting pretty oiled down so I'm planning on removing my oil injection and running a good new bit of mixed gas just to confirm that my injection system isn't providing too much oil. This issue has been pretty frustrating for me as well and has ruined a handful of otherwise good boating days. Hopefully we can get to the bottom of it.

 

[55evinrude]

Re: 199 40HP 2 stroke Merc stalls at low idle

idle circuit is the first thing to check, when a motor "pops" it means its running lean generally caused by gummed up idle circuit passages and you will notice if you choke it the popping will go away.

 

[Otis313]

Re: 1999 40HP 2 stroke Merc stalls at low idle

Re: 1999 40HP 2 stroke Merc stalls at low idle

Was at my marine service place to pay the storage bill, and mentioned the problem to them. They offered to check it out for me and see what they could find. The mechanic reported he found some of the carb linkages were loose, so they were corrected and he bumped up the idle speed a bit as well.

Hope to get it on the water this weekend and will report back if the problem has been resolved.

 

[Otis313]

Re: 199 40HP 2 stroke Merc stalls at low idle

Well, the idle issue has greatly improved... started, idles and shifted much better. It only stalled on me once all day. The downside is that it seems to have created another problem. The boat felt sluggish right from the first application of the throttle. We used to get 44kph at 5500RPM but on Sunday I was only getting 36 or 37kph and 5100RPM at WOT.

Dropped the boat back and asked them to have another look at the carb and settings.
Will post another update again once I hear back.

 

[Polara Pat]

Re: 199 40HP 2 stroke Merc stalls at low idle

Well, the idle issue has greatly improved... started, idles and shifted much better. It only stalled on me once all day. The downside is that it seems to have created another problem. The boat felt sluggish right from the first application of the throttle. We used to get 44kph at 5500RPM but on Sunday I was only getting 36 or 37kph and 5100RPM at WOT.

Dropped the boat back and asked them to have another look at the carb and settings.
Will post another update again once I hear back.

Get a quick compression check while your at it.

My news isn't so good. I found #2 and #3 down around 35 pounds so I tore off the power head and I could clearly see with the exhaust cover off that #4 has a broken ring and serious welded deposits on top of the piston. Looks like I'll be dry docked for a while.

Good luck with your project and sorry about the thread hi-jack.

 

[Otis313]

Re: 199 40HP 2 stroke Merc stalls at low idle

No worries Pat, if you're having a similar problem, then its no hijack. Ill ask about a compression check while they have it apart.

just pray my issue is not as serious is yours... Sorry to hear the bad news - Good luck with the repairs. Hope you're not out of the water too long.