1999 115hp Merc Problems Please Help

[bbjohn74]

I have a 99' 115hp Merc that I have owned for about 2 years now and it seems that it never has run very "well". I'm not sure how long it sat before I bought the boat, but it started right up. It is on a 24' Pontoon boat. I thought after a good tune up and clean gas it would run fine. I have replaced the fuel filter and plugs several times now and it seems to run a little better. But about two weeks ago I replaced the fuel filter again and I had a hard time keeping it started. Once we ran it around for a little bit, it started running fine. But as always when I am idling around it runs like a tractor. It feels like it is missing on at least one cylinder. When I am giving it gas taking off, it really kicks in hard at 2500rpm. As I give it more gas you can still hear it trying to spit and sputter then after that it is fine. I have read some of the other posts about these and some of you mentioned that there were some years that Merc went to 2x4 type system. Meaning it runs on 2 cyl. at idle to 1800rpm then all 4 cyl kick in. What controls this ? Any ideas what else I should look at ? I know this is long and I appreciate any help. Thanks, John

 

[Drybo]

Re: 1999 115hp Merc Problems Please Help

I'm not the expert, someone jump in and help. I do know to check/ change fuel bulb see if it stays hard, check fuel pump diaphram(common problems , both easy fixes). Squeeze fuel bulb at idle to notice rpm change. There's more help if they will check out your question.

 

[emzle]

Re: 1999 115hp Merc Problems Please Help

No expert here either, but i just worked on mine for a month before finding a bad CDM module. I agree that you do need to make sure the fuel pump, primer bulb and filters and spark plugs are all funtioning correctly. I would also check the timing, and idle mixture settings (a manual too). They are notorious for rough idle, but will tune in pretty good with the right settings.<br />#3 and #4 cylinder kick in when the fuel mixture is suitable for combustion, around 1800 rpm. Good luck and look for some good help here from some great people.<br />mark

 

[BikerBoater]

Re: 1999 115hp Merc Problems Please Help

Have you rebuilt the fuel pump? Inexpensive $10 and may be your problem "fuel pressure".

 

[bbjohn74]

Re: 1999 115hp Merc Problems Please Help

I have not rebuilt the fuel pump yet. It seems to run fine once warmed up and half to full throttle. It's idling that it doesn't like. Thanks for the advice I will check everything as soon as possible. It's finally getting on my nerves enough to make me want stay on it until it is fixed. And who the H#!! came up with the idea of 2x2. Sounds like more problems than it's worth to me.

 

[tengals123]

Re: 1999 115hp Merc Problems Please Help

have you checked your timing and carb synch??<br /><br /><br />cheers