1994 150hp merc surging at 4000 rpm

[Panaseaya]

Please help!! I have a 1994 150hp merc outboard that has been giving me some problems. The motor will maintain about 4,000 rpm when it will usually hit 5,500 with no problem. I can back off of the problem and floor it and it will hit the 5,500 makr before dropping back down to 4,000. I had the dealer replace the water pump the poppet valve after he said that the poppet valve may be the issue causing everything. Since I got it back for the shop, I tried it out once again with no difference. My next step was to replace the primer bulb, replace the plugs, and rebuild the fuel pump. Tried it again with no difference. Can anyone suggest what my next step should be? I have ordered some carb rebuild kits thinking that may help, but before I break them down, I would like some input as to what else may be causing the problem. Should I check the spark on my plugs even though they don’t look fouled and are new? If so, where would I find a spark tester? Sorry for all the questions, and thanks for the help.

 

[Panaseaya]

Re: 1994 150hp merc surging at 4000 rpm

sorry, I meant back off of the throttle, not problem!

 

[LubeDude]

Re: 1994 150hp merc surging at 4000 rpm

I can't help but think that it must be some type of a fuel problem. You seem to have addressed everything but the vent in the tank. Critters like to build nests in the vent tube. Check it out.

 

[Panaseaya]

Re: 1994 150hp merc surging at 4000 rpm

Well, I finally made it home and checked the screens on my Fuel overflow spout and they are not obstructed. Is there a check valve that may be behind the screens that I can't see that may be sticking?

 

[Panaseaya]

Re: 1994 150hp merc surging at 4000 rpm

I forgot to add, I changed the water seperator and fuel filter before doing any of the above to rule out those issues.

 

[andy6374]

Re: 1994 150hp merc surging at 4000 rpm

IF you rebuild the carbs and it does the same thing, I would have to guess that you are losing spark intermittently. Sometimes this happens when an ailing switchbox gets hot.

 

[MercFan]

Re: 1994 150hp merc surging at 4000 rpm

Other things to check are blocked fuel strainers at the carbs. Debris floating in fuel tank. And air being sucked into the air line. Check fuel line fittings between tank and fuel pump.<br /><br />But it's always good to rebuild the carbs, that rules them out in future.

 

[Panaseaya]

Re: 1994 150hp merc surging at 4000 rpm

I just wanted to say thanks for the help. I've gotten the surging problem fixed, but now have an oil problem. The surging problem was the carbs, I rebuilt the carbs and now she'll run good! Now I have an oil problem which I think I can figure out based on the info found on the search pages. Thanks again, you've all been a great help.