Can not get my boat over 2,300 Rpm in the water omc 2.5L 120hp

[If_the_boat_floats]

I am about out of ideas... I posted a similar post a while back still havent got the issue figured out. Here is what I have done. I have compression tested it 120 on all 4 cylinders, I have replaced spark plugs 3 times, they were getting carboned up, I have replaced the plug wires, I have replaced the coil, the cap and rotar look great, adjusted the points they were .006 too closed, I have adjusted the timing to 4? btdc, I cleaned the advance weights they seem to be operating properly, I replaced the fuel line and anti syphon valve, i have replaced the fuel pump and filter, I have replaced the oil in the gear box upper and lower I have cleaned the carb and rebuilt it... only things I have left to question... i don't have a timing light with advance. my boat is an omc it has a black carb on it.... could this be off or a mercruiser 3.0 and could it be too big for the engine? What size is the correct jet size for a 2.5l? I'm really wanting to get the last couple weeks of summer out if this boat... it does run better than it used to. Just can't go over 2300rpm... it did plane out one time and got to about 3,900rpm that was prior to all that being done. all i had done at that point was fuel system cleaner and new plugs. After i went to shore and fired it up it ran like crap... found my distributor to be loose timed and I ended up running it out of gas that day but it never planed out after that. it boggs at WOT runs best at three quarter throtle. the boat runs great out of the water in my driveway with muffs...

 

[If_the_boat_floats]

This is the carb I know it's not the one that came on the engine

 

[zigbat]

I am not an expert by any means, but when my boat wouldnt get to the proper RPM
it was because the cables/linkage was out of adjustment and the linkage hit the cable before the carb was wide open..
Have you checked to see that the throttle plates are opened fully when its wide open..
If not maybe that would be a jump off point to figure out the problem...

 

[If_the_boat_floats]

Yeah unfortunately I have checked that.... also when i go to WOT it bogs out.... and my accelorator pump does work too... I'm wondering on if that carb has bigger jets or if my float could be causing this I dunno

 

[Scott Danforth]

its almost never the coil

use a dwell meter to set the points after you file them the feeler gauges get you in the ball-park.

set timing at idle, in gear, and in the water.

clean the carb. BTW, the carb is a transplant.

replace the bushings on the carb linkage that bolts down to the bell crank on the manifold. that is a common issue with old OMG's and the throttle not opening.

 

[If_the_boat_floats]

its almost never the coil

use a dwell meter to set the points after you file them the feeler gauges get you in the ball-park.

set timing at idle, in gear, and in the water.

clean the carb. BTW, the carb is a transplant.

replace the bushings on the carb linkage that bolts down to the bell crank on the manifold. that is a common issue with old OMG's and the throttle not opening.

as far as the throttle not opening i have looked at that in my drive way would it be in anyway different on the water... also do you know the jet spec... im wondering if i need to go down on my jets... ive heard of other people having rich problems and going down

 

[Scott Danforth]

most likely its not your jets. reading the plugs will tell you if your lean or rich. cant go off what someone else's problems were.

I would start with making sure your timing events are proper. start with a dwell meter and go from there.

second, get a carb kit and completely soak all the components, then pass wires thru every passage. make sure you change the inlet filter to the carb.

I know on my OMG, if the dwell was off, it ran like crap.

 

[VE8EV]

I am about out of ideas...
...and I ended up running it out of gas that day but it never planed out after that....

I know you said you replaced everything but it sure sounds like some kind of blockage from crud sucked off the bottom of the tank...

 

[If_the_boat_floats]

I know you said you replaced everything but it sure sounds like some kind of blockage from crud sucked off the bottom of the tank...

and thats another thought ive had... i gave up and took it too a shop today... lol ive put so much time into it this summer im done for now hopefully they will figure it out.

 

[If_the_boat_floats]

most likely its not your jets. reading the plugs will tell you if your lean or rich. cant go off what someone else's problems were.

I would start with making sure your timing events are proper. start with a dwell meter and go from there.

second, get a carb kit and completely soak all the components, then pass wires thru every passage. make sure you change the inlet filter to the carb.

I know on my OMG, if the dwell was off, it ran like crap.

when i brought it to the shop he said something abut jets as well