1998 Merc 115 2cycle 4cylinder

[strids97]

Quick question, these motors run max RPM's of 5250. Has anyone ever tried adjusting the rev limiter to see if they gain any performance? Been messing with maintenance on my engine (new plugs, fuel filter) and just wondered, not brave enough to try it...LOL

[IAm4DaKing]

How is the transition from running on top 2 cylinders to all 4? Is it smooth or does your motor hesitate a little bit? Lower 2 kick in around 1600-2000 rpms depending on load? This is off topic but I wanna figure out the issue with my motor and have the same one you do.

[vicks]

Mine hesitates

[IAm4DaKing]

So does mine. With 2 people I can't get on plain. And its not a prop issue either

[06 SB]

It believe it is not adjustable. What boat are you running it on and what prop?

These motors will hesitate slightly as the two cylinders come on line. With a good lync&sync it will be barely noticable.

[IAm4DaKing]

Mine did too but I think I figured out the issue. First check fuel lines to make sure there is no air sucking in anywhere then check out carbs and stater, regulator, coils maybe. Could be allot of small things

[JOE54]

not adjustable

[TDobb]

Same motor except a Mariner. My fuel line going into the front of the engine split slightly and I think it is cause the fuel line is too tight when turned all the way starboard. Will be doing the fuel line tonight most likely.

[strids97]

It believe it is not adjustable. What boat are you running it on and what prop?

These motors will hesitate slightly as the two cylinders come on line. With a good lync&sync it will be barely noticable.

Mine doesn't hesitate, it's pretty instantaneous. I'm running on a Ranger R70 with a 22 Laser II. I'm just looking and curious if there is more with these engines or if what is there currently if that is it? Like I know with the older 2.5liter blocks they would continue to produce HP as the RPMS went up, just curious if you got these engines to say 5500RPMs would you gain anything.

It actually is adjustable, currently from the factory there is a hard plastic gew on the screw so it's not messed with but they can be adjusted. Just curious if I would gain anything. if not won't mess with it, if I would might try but don't want to damage engine either as trying to save for a new boat not put more into this one.

[06 SB]

All I heard from a local mechanic when I had it checked out was that there are harmonic issues with the motor above 5250. Much above that and it will go BOOM. If you cannot feel the hesitation then it is set up perfectly. You have the best you can get out of it already.

BTW, I hope you have changed out the original fuel lines on the boat. The ones from that area easily deteriorate.

[JOE54]

he was right idealy need to be propped right on 5250 with normal load

[strids97]

All I heard from a local mechanic when I had it checked out was that there are harmonic issues with the motor above 5250. Much above that and it will go BOOM. If you cannot feel the hesitation then it is set up perfectly. You have the best you can get out of it already.

BTW, I hope you have changed out the original fuel lines on the boat. The ones from that area easily deteriorate.

Actually just did the tank to water filter 2wks ago, what was in there didn't look original but everything from filter to engine was changed when I bought the boat 5yrs ago, and then again by Ranger dealer when I changed the original Yamaha that came on the boat out for the Merc. Yamaha died a month after I bought the boat.

If anything over 5250 causes harmonic issues I won't touch it, I just put a Hydraulic Jackplate on it earlier this year and still trying to find the sweat spot, but also realized i've just put too much crap in the boat...LOL keep adding more tackle without taking stuff out. Going to try and get some of that out and lighten it up some. 2016 I could easily get 50-51mph out of it by myself and 48-49 with another person and full livewells, but prop needed work last year and after I moved to my new house never really took much out that I had put in the boat so most likely on the heavy side. Best i can do now is 46 and the only change was the Jackplate which should improve it. Just making sure i wasn't missing out on anything else. I will just keep messing with my setup and weight distribution and go with that. Thanks for the info....appreciate it.

[JOE54]

light is fast, LITHIUMS

[strids97]

yeah those are expensive though :) just put all new batteries in last fall. I just need to get in the habit of not carrying so much stuff...LOL I have all my tackle organized so I can easily change things out depending on where i'm going but i still keep it all in the boat...just a habit I need to break. When I can get a new boat with a larger engine that has more storage won't be as much of an issue.