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Calling all 2 + 2 Merc./Mariner Owners

V

Vlad@

New member
Own a 1989 100hp Mariner and still can't solve the poor mid-range performance issue on this 2 + 2 engine.

Engine starts right up, runs and sounds like a new engine below 2000 and above 4000 rpm. Between 2000 and 4000 stumbles and loses power. Slam the throttle forward the accelerator pump deliveries the fuel to #3 & 4 cyl. and it takes right off, move the throttle forward slowly and it will take about 5 seconds for those two cylinders to kick in. Bring the throttle down from WOT and as soon as hits 4000 the problems begin.

Rebuilt the entire fuel system, pump and carbs twice thinking I screwed up the assembly, new plug wires and switch box. Tested all electrical components, with the exception of the stator and link and sync. the engine half a dozen times.

I understand these engines are known for poor mid-range performance, but I was hoping someone that has experienced the same issue and resolved it could share their fix. I've run out of solutions.

This engine is becoming an obsession and think my wife is going to divorce me and take the kids. I love my Mariner.
 
Make sure you did not mix up the carbs, get the factory(MERCURY) service manual and set it up (link and sync) step by step according to the book, no short cuts.......



THIS HAS TO BE DONE IN THE WATER!!!!
 
I have the same engine and let me tell you the best thing I ever did was replace the carbs with 115 carbs. I picked up a complete set of 115 carbs on ebay for cheap. I then rebuilt them and installed. It's like a new motor!
 
A good friend of mine has the 115 2+2 motor. It is in excellent shape. I have tried to fine tune it for him and gotten it the best that I could. As I am sure you know, only the top two carbs have an idle mixture screw. Seems as there is a fine line between a sluggish, stumbling idle (jets set too rich) and a decent idle (jets set a little leaner.) Either way, the idle is lackluster at at best. What I noticed is that if I richen up the carbs, the midrange improves some, but if I keep them as lean as I feel they need to be for a smooth-ish idle, then mid-range suffers even more.

He says pulling skiers is a nightmare!! He has to hammer on it to get the other 2 cylinders to kick in and get the hole shot he needs. If he does not slam the throttle, it is similar to what you have going on where the motor will be sluggish and then suddenly take off like a bat out of hell.

I guess, in my experience, what I am saying is those motors can only get as good as they can get. The symptoms that you describe are the same that he has on a professionally rebuilt fuel system. The way that he gets around it is to just lay into her to get on plane, and then ease back off the throttle to 3-4000rpms for cruising. That is much more effective that easing the throttle into the cruise zone.

Don't drive yourself nuts over this motor. They do what they need to, but are a poor design (IMO) and were very tough to tune properly. Don't be losing any wives over this engine!!!
 
I have owned that motor and it is still one of my favorites. Don't let people tell you they don't idle well because they are a smooth idling motor. I used mine for tubing,skiing and fishing which included a lot of trolling. They have very good mid-range power. Look at post #2 and get the factory service manual. The rough idle will usually come from the bottom 2 carbs leaking and those cylinders trying to fire. You also need to check the stator that is a weak spot on them.
 
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