Mercury 40elpto has got me stumped..need help

[hawkf250]

Hey guys, Im stumped on this one. I see alot of motors come my way with low power issues and usually it is carbs or spark or fuel ect. but this one has me. A guy brings me this motor which is a mid 90's? beljum mercury 40elpto oil injected. He sais one day was running like a champ, the next day it wouldnt go on plane or break 2500 RPM. I took it in, checked spark, good blue spark to all 4 plugs soaked and cleaned the carbs, full link and sync checked compression and fuel delivery. All checked good compression was a little on the low side but good and even. Put it in the water Idles perfectly go to WOT it will rev to 2500 rpm and that is it. However it doesnt sound like its bogging or trying to dye its almost as if it is just at half throttle or something. I re-checked the link and sync and the butterflies are opening straight like they should. Im thinking that the advance on the timing is not correct or not advancing at all. What would be the symptoms of that or would one thing a bad trigger maybe? Or am I way off on this. Please help, I dont know what else to do.

Thanks

 

[jimdd810]

Re: Mercury 40elpto has got me stumped..need help

I would check the fuel pump first. I had one that did what yours is and would idle all day long and not get over 2000 rpms.

 

[hawkf250]

Re: Mercury 40elpto has got me stumped..need help

I will check that in the morning and post my findings. Thank You

 

[milehighboater]

Re: Mercury 40elpto has got me stumped..need help

pull the prop, make sure it is not binding up.

 

[Faztbullet]

Re: Mercury 40elpto has got me stumped..need help

If fellow does a lot of trolling check to see if a chunk of carbon has built up/broken off and blocking exhaust can....

 

[hawkf250]

Re: Mercury 40elpto has got me stumped..need help

Ok... here's the update, and thank you all for the quick replies and great sugjestions. Still havent fixed it but I am getting closer. I checked the fuel pump, it is good. pulled the prop, no restrictions and am getting good exaust flow. I changed the plugs and cleaned the wires and took if for a ride, still same problem. Then I treid the old pushing the chocke trick again (primer soleniod) and at first nothing at all, but this time I guess out of frustration, I just held it in a while longer and slowly rpms began to climb....so now Im back to the carbs, which is just as frustrating. I let them soak for two days, put a full rebuild kit in them with all of the little orfice caps and all, and blew it out with compressed air and got good airflow through all passages. what else could be restricting flow?

 

[Dave1027]

Re: Mercury 40elpto has got me stumped..need help

Still sounds like fuel pump or a restriction in fuel line or tank. Have you checked the primer bulb while running? Is it collapsed? Have someone squeeze it while under load to see if RPMs pick up.

 

[hawkf250]

Re: Mercury 40elpto has got me stumped..need help

Yes, while I was running it I was squeesing the primer bulb to see if that made a difference and it did not, also I put a clear filter on to see if I was getting any bubbles and was not. The primer stayed nice and firm through the duration of running it.

 

[jimdd810]

Re: Mercury 40elpto has got me stumped..need help

is your vent completly open and free of restrictions? Sounds dumb but if I had a dollar for every time i went out to check a customers boat and found the vent closed or plugged id be a rich man.

 

[CharlieB]

Re: Mercury 40elpto has got me stumped..need help

An internal split/flap in a fuel line between the primer bulb and the carbs will restrict fuel flow and limit RPM without sucking the bulb flat or show bubbles in the line near the carb.

Pull the fuel line from the carbs, point it into a suitable container, fire up the motor or squeeze the primer, and observe for a weak fuel stream. If not a strong pulsed stream then start pulling the line and testing flow farther back till you get a good stream, replace the faulty section.

 

[hawkf250]

Re: Mercury 40elpto has got me stumped..need help

Ok Problem solved.... Sorry it took so long for me to get back to you. You all were right. it took a little more digging but sure enough a faulty check valve in the tank outlet, leaking primer bulb (new but still bad..ERRR) and a restriction that was in the lower carb. fixed all of that and she's back to full power. Thank you all for the great input I guess sometimes the simple things throw us from time to time.

 

[talltails22]

Re: Mercury 40elpto has got me stumped..need help

I have the same motor same action and as hard as it is to believe it was the fuel connection sucking air. Pull them off and really reset them and good to go, as least it was on mine. would run all day at what seemed 1/3 throttle

 

[123roger]

Re: Mercury 40elpto has got me stumped..need help

When you say "it was the fuel connection", do you mean where the fuel line connects to the motor?

 

[talltails22]

Re: Mercury 40elpto has got me stumped..need help

On mine it was the connector at the tank. It seemed to be seated even through pumping the bulb and such, motor ran but all of a sudden would slow down , it could run like this all day perfectly. Later on further inspection the connector just slipped off. Now I treally seat the connector and then pull to make sure it is FULLY snapped on, and had no further issues, hope this helps as it can be very frustrating/ costly