1988 50HP not reving up

[Kidmon]

Help, I am new to boating world. I now have a 20ft. pontoon with a 1988 50HP force engine that seems to run great, it just does'nt seem to rev up. I can manage only 7mph on the pontoon at full throttle. The engine runs very smooth at all speeds but it just does'nt seem to rev up. (Sorry no tacometer on the boat) I changed the spark plugs, impeller, lower unit oil, new gas/oil mixed with Seafoam added. We ran the boat for 4 or 5 hours on the lake with no problems just slow speed. The gas tank does seem to build alot of preasure as it sits in the sun, the fuel line bulb does get hard as we pump it. Any help would really be appreciated, We love our pontoon but I know it will run a bit faster.
Thanks for your help Guys.

 

[Stanley1]

Re: 1988 50HP not reving up

If the gas tank is building up pressure that would seem to indicate that you do not have the vent open. This would cause your motor to be starved for fuel. Try opening the vent on the gas tank. There should be a knob in the center of your gas cap which when opened allows air into the gas tank.

 

[crazyinkc]

Re: 1988 50HP not reving up

I too have an 88 50hp on my 88 Sea Nymph 20ft pontoon and I have the same problem. I belive mine is the controls. They seem very cheap and sloppy. The motor end isn't much better. I see a lot of slop in the vertical shaft that drives the throttle cam and timing base. I get full advance on my timing but I cannot adjust the rod out to get full throttle. If you look at the carb throttle shaft you will see the double "D". it should rotate 90 deg. Mine only goes about 60 and that is the best I can do. I have tried adjusting the cables many times and no help. My shift cable seems to always go out of adjustment. I am going to buy a new set of controls and see if I can get it to do what I want it to do.

 

[Kidmon]

Re: 1988 50HP not reving up

Thanx for you help Guys.
It turns out that after a lot of testing with a ohm/vollt meter that I have a bad Trigger that only fires one one cylinder. The vent cap I am still trying to figure out because my tank has no vent in the lid anywhere so I am wondering if there is a vent system in the "Quick Coupling" for the fuel line. As far as the linkage my linkage is new and a very good quality it works great. The guy I bought the boat from just put it on and spent over $300 bucks for it. Thanx again for your imputs.
Ken