89 Merc 115 not going past 2000 rpms

So I have an 89 Mercury 115 2-stroke. Serial Oc106309.*

Ran normal for most of the weekend. Slow trolled for a bit and when I opened it up it wouldn't go past 2000 rpms for probably 30 minutes. Bumped up to 3 grand from 30-40 minutes and then opened up all the way and ran faster then it has since I've owned the boat. So about 50 minutes of limited rpms then ran like a taped ape.

Recently changed the impeller and temp sender. Had a very brief alarm go off at the beginning of the second day of our trip that was a solid beep for several minutes, went off and then screeched and chattered for a couple minutes a little later

​​​​​​​Thanks for any help!

So you kept running it with the overheat alarm going off.-----Motor complained and chattered ??------Best to do a compression test.------Perhaps shop for a new motor !

It was very brief and I had water from the tell tale and the block was not hot. Just checked compression 2 weeks ago.

Cleaned all 4 carbs and replaced both fuel filters. Took it to the lake where it seemed to be running normal but ended up getting stuck at 1500 rpm later in the day and was running very rough.

Trailered it and pulled the plugs, all 4 which were fouled with oil residue. Cleaned them with some carb cleaner and a rag and went back out. Was immediately capped at 3000 rpm with the throttle wide open, so better but still garbage. Called it a day after that.

Any ideas?

I rechecked compression which is 90 psi across all cylinders. Spark is great off the plugs. 260 volts across each coil. Throttle linkage is clean and operating normal. All carbs open in sync with the throttle. Does this mean I have a fuel issue?

Being a 2+2 carb setup, is it reasonable to think the issue is with the bottom 2 cylinders?

Metallife89 said:

I rechecked compression which is 90 psi across all cylinders. Spark is great off the plugs. 260 volts across each coil. Throttle linkage is clean and operating normal. All carbs open in sync with the throttle. Does this mean I have a fuel issue?

Being a 2+2 carb setup, is it reasonable to think the issue is with the bottom 2 cylinders?

Click to expand...

I am interested in what you find as well. I have an 87 Mariner 115 with similar issues. Only other thing I plan to check is the fuel delivery. That will be a couple weeks before I can get to it......

Tore fuel pump apart and the diaphragm were hard like a speaker cone. Replaced them so we'll see how things go this weekend.