1997 Mariner 115 2+2 wont go above 2,000 rpm

[rcwannab]

I have a 1997 Mariner 115 2+2 (serial#: OG498217) on a 17' Alumacraft.
It has been flawless for me since I acquired it in 2002.

I removed the outboard last winter to complete transom replacement.
I just got it in the water 8/18/18 and the motor started up great, idles fine, and runs flawlessly up to about 2K rpm.
I can bury the throttle, but nothing additional from the engine.
Throttle cable adjustment is good, has spark, has compression, prop hub is good, all carbs appear sync'd.

Figure I'll start with the carb rebuild. Looking for suggestions towards diagnosis.
Thanks in advance.

 

[TenE3072]

I had a 91 mercury 100 hp 2+2 that had the same issue and it was caused by a spring and ball connected to a line going into the cylinder. It was there to lube the other cylinders when running on the 2 cylinders. I would look at the spark plugs and they were wet. I had to take the spring out and stretch it so it would hold the ball in. I made a thread a long time ago but cant find it. It was a part I could not find on normal diagrams but was able to see it on the manual at the boat repair place.

 

[TenE3072]

Found the topic

https://forums.iboats.com/forum/eng.../136294-even-stumped-my-mechanic-update/page2

 

[rcwannab]

Thank you for the input I will look into this.
The knowledge base and willingness to help on this forum is fantastic!

 

[rcwannab]

TenE372 - I found this in the service manual

 

[rcwannab]

Removed the four carbs last night in preparation for carb cleaning and rebuild.
Interesting observation this morning the two top carbs had drained some mixed gas and the bottom two drained what appears to be mostly oil.

 

[rcwannab]

Cleaned accelerator check valves, rebuilt fuel pump and rebuilt carbs. Engine starts better than it ever has. Idles too high and needs to turned down. First couple trys on the water advancing throttle would get to approx 1800 rpm and then just dog. Finally it coughed and sputtered and got up to 5000 rpm. As I ran more it seemed to improve, however what used to be a seamless transition from two to four cylinders kicking in is now very noticable. Will lync and sync. But getting better