Merc 125 improvements?

[hughie93]

I have a 2000 Merc 125. I can't find any aftermarket performance items for this motor. I've done a few small things, (Jack plate, setback, prop, and steering.) The trouble is, I would like to get rid of the rev limiter, or put an adjustable one on. Exhaust box would be another. I currently run a 15' checkmate. Any help would be greatly appreciated. Thanks, Chris

[natzx7]

I have heard of people talk about bypassing the 2 - 4 mode but I have never seen it done. Anybody?
welcome to the board hughie93 :D

[Raceman]

I don't know much about those motors except for the fact that a neighbor has one on a pontoon, but the local machinist, who has done powerheads for years, some for Merc's old Pacemaker program, says the cranks in em are the weak point and they won't live in performance applications, especially when trying to raise the RPM's.

[Markus]

Chris,

Raceman is right. Supposedly, there is a resonance problem not too far above 5200 RPMs (or wherever the rev limiter kicks in).

The Merc. inline 4s were designed for the U.S. walleye market, thereby the 2+2 trolling mode. It is not built for performance, and as far as I know, there are no performance bolt-on parts available unless you count propellers and reeds.

If you want more power, get a 2.5 liter V6 Mercury. That is a way better design. Or you could go with a Yamaha V4 and start modifying that (or an OMC V4 unless you are afraid of the quality issues with OMCs).

As you may have noticed, Mercs Optimax engines in the 75-125 hp range are not based on the current 3/4 cylinder monocast design. Instead they went with a 3 cyl 1.5 liter block using as much of the 3 liter parts as possible.

[Vicious One]

Sell it and find a 135 v-6, or and older inline 140-150. You can't do a damn thing to those motors, and the crank will break if spun past 5700 or so. Not to mention they sound like they are going to fly apart at that rpm. I have an 88 100 i use for fishing and it works great, for fishing.Capt Insane-o out.:eek:

[Jeff_G]

We looked at it for racing in the Formula V class. We can remove the rev limiter, change the 2/4 set up, do port and head work and all the other things for high performance. Unfortunately we can't get past the crank issue. They WILL break anywhere close to 6,000. So we abandoned the project. I really wish it would have worked would have given us new motors for the class.
We are still looking though.

[Looper]

My friend has one that I work on on her whaler. How do you get rid of the 2/4 set up? It is not a very smooth transition when trying to get on plane or pull a skier. I though it had bad coils/power pack until I found out here about the "feature".

[MX-14]

I run a 3 cyl Merc 90 at 6800 all day....today for example!! It sounds good and handles it. I was told not to go over 6200 or I would break the crank, so I have been trying to break it.... not yet. :cool:

[MX-14]

I ran at 7100 for about 2 minutes today...not on purpose, I took my eye off the tach.

[natzx7]

I've got a brand new 2002 125 for $4900 if anyone is interested -last one. -Nat
I also have a new leftover 99 135 that somebody stole the carbs and top cowl off :mad: :mad: :confused: It is a 25" counter rotator I will sell for $3975. If you need the carbs and cowl I can get them for extra but if someone has these parts laying around it would be a good deal for somebody.

[hughie93]

Thanks for all the input. I began to have some doubts when it was difficult to find parts for. In hindsight, I should have popped for the 2.5 or kept playing with the 2 straight sixes I had in the garage. I'll just keep plugging with what I have. Thanks again!--chris:)