1998 115 ELPTO Running Rough at certain trim positions

[codertimt]

Okay, I'm acting as proxy for my Dad with this post, so I might not have all the information needed for problem solving, but I thought I'd ask and see if there was any kind of consensus...so here goes.

My Dad just purchases a 1998 Ranger R77 with 115HP Merc. When puttering along barely above idle, if the motor is trimmed all the way down it will start stumbling/running rough...basically not getting fuel. He also had it cut out on him running down the lake when trimmed out fully... When not trimmed to the extreme in either direction, it's running great.

According to the seller, the boat mechanic he brought it to told him it was caused by the angle of the motor and was normal.

I agree it's caused by the angle of the motor, but it doesn't seem to me like it should be normal. Where should he start looking? Float level?

Also, from doing some searches on rough running 115's, I'm seeing references to this motor only using carbs 1&2 at low rpms. Does it drop 2 cylinders entirely at low rpms?

Thanks for any info/ideas.
Tim

 

[Laddies]

Re: 1998 115 ELPTO Running Rough at certain trim positions

Any float type carb that is tipped will cause the mixture to change, out is lean and in is rich. Just a a glass of water will spill as when filled close to the brim and tilted to the side.

 

[codertimt]

Re: 1998 115 ELPTO Running Rough at certain trim positions

Any float type carb that is tipped will cause the mixture to change, out is lean and in is rich. Just a a glass of water will spill as when filled close to the brim and tilted to the side.

Thanks for the response...

So, just to clarify, you're saying this is most likely normal, even at "normal" trim levels? It does tuck under the boat pretty far when trimmed down, so sits at a pretty decent angle... I don't know how far the motor was trimmed up when he experienced problems...it was before porpoising or blowout though....

I guess it's just kind of unexpected. Most of my experience has been with Johnson crossflow v4s. You basically had to trim the prop out of the water before it would stop getting fuel...

Again, thanks.
Tim

 

[Laddies]

Re: 1998 115 ELPTO Running Rough at certain trim positions

His problem you said was trimmed under at idle and that is causing the engine to stumble (load up) there is the possiblity that the floats are a little high (it's hard to hear from where I'm sitting) that could add to the problem but the dealer telling you thats normal is the truth, he is simply causeing the engine to flood why would he have to run it in such a unnatual position for, is there a problem with to much speed at idle or what?

 

[codertimt]

Re: 1998 115 ELPTO Running Rough at certain trim positions

His problem you said was trimmed under at idle and that is causing the engine to stumble (load up) there is the possiblity that the floats are a little high (it's hard to hear from where I'm sitting) that could add to the problem but the dealer telling you thats normal is the truth, he is simply causeing the engine to flood why would he have to run it in such a unnatual position for, is there a problem with to much speed at idle or what?

Come on, you're only like 800 miles away...maybe it's time for a hearing screen...

He doesn't have to run trimmed down...just kind of habitual operation... Running slowly out of the no wake zone, we're used to trimming down in preparation to take off once you clear the no wake zone. In this case you can only trim down fully right before applying significant throttle.

I definitely understand the theory, but I guess I wasn't considering normal trim levels to be unnatural....

Thanks again for your help. I'll pass the information along and let him decide what, if anything, he wants to do about it...

 

[j_martin]

Re: 1998 115 ELPTO Running Rough at certain trim positions

On a bass boat, with everything in the back and the motor tucked under, it's likely to flood a little. Normal operation would be to trim it level for no-wake, and tuck it in just as you hammer down for the blastoff. With a couple of head turns, you should be able to get a fix on where the trim indicator is when it's level.

At full trim out, though, I wouldn't think it should fail. If'n it were mine, I'd get the carb kits and go through them, just to be sure they have the right jets in them and everything is adjusted to the book. It could be 2 seperate problems, like flooding when tucked in, and running short of fuel at WOT.

hope it helps
John

 

[codertimt]

Re: 1998 115 ELPTO Running Rough at certain trim positions

On a bass boat, with everything in the back and the motor tucked under, it's likely to flood a little. Normal operation would be to trim it level for no-wake, and tuck it in just as you hammer down for the blastoff. With a couple of head turns, you should be able to get a fix on where the trim indicator is when it's level.

At full trim out, though, I wouldn't think it should fail. If'n it were mine, I'd get the carb kits and go through them, just to be sure they have the right jets in them and everything is adjusted to the book. It could be 2 seperate problems, like flooding when tucked in, and running short of fuel at WOT.

hope it helps
John

Thanks for the input. I will relay the information. After speaking to him again today, there might not be a problem at all at WOT anyway. Apparently, it didn't just die or anything, it just seemed to drop off in rpms... Well he noticed today that when he take his hand off the control, the throttle will creep back up...apparently it's a bit too loose. It's been quite windy and rough here lately, so it's quite likely the problem was just the throttle changing position on him...

Again thanks for the help.
Tim

 

[pops]

Re: 1998 115 ELPTO Running Rough at certain trim positions

My 1995 115 Mariner (same design) does run slightly rough if trimmed all the way down at slow speed. As JM posted, I try to keep it level at low speeds and trim down only for take off. However, I have never experienced any problems at WOT, regardless of how the motor is trimmed. I would say that any stumbling, etc. at WOT indicates some type of problem that could definitely be fixed by a competent technician.