Force 50, 4200 RPM top speed.

[glennkil]

Appreciate any advice on the reason why my 1988 Force 50 will only run to 4200 RPM at full throttle. It starts perfectly, runs smoothly and blasts out of the hole but will not rev past 4200 RPM. Was 4000 RPM until I adjusted the trim with some well placed bolts taking Franks advice until I can repair the tilt and trim.

I have pumped the primer bulb furiously at full throttle but no difference.
I have checked the carb butterfly position with the engine off and the throttle pressed all the way to stop in the forward position and I am NOT getting a horizontal butterfly. it's about 75% open. Now the confusion.

Should you do the adjustments on the carb linkage with the forward control set to full throttle OR move the mechanism on the timing tower to full throttle and then check for horizontal butterfly?? Does this make any difference? I haven't peered down the carby at full throttle with iPhone torch on the water and don't really want to Will the engine running alter the mechanism and enable the last 25% of butterfly movement?

Is this likely to be the issue? I don't know what the prop is. Boat is nearly 16 foot and maybe underpowered with the little 50? It doesn't labour up to the current 4200 RPM, accelerates hard but that's it when get to that RPM. Many times I try and push the throttle forward and find its already on the stop. I haven't done a compression test but I guess its possible its low but runs so sweet and strong to the current limit.

I haven't cleaned the carby out either and am not sure I fancy pulling it apart and finding I need gaskets or parts that are notoriously hard to find in the land down under. Appreciate any help.

 

[pnwboat]

Sounds like there may be a linkage adjustment issue if the butterflies are not close to being horizontal.

Also the propellor pitch should be verified. If the blades have too much pitch, the motor may not have enough horsepower to operate at the recommended RPM's. There should be some numbers on the propellor that may be helpful in determining what the pitch is.

 

[jerryjerry05]

Have you tried to advance the throttle(at the carb) all the way once your up on plane?
How much does your boat weigh?
How big a load?
Size of the prop?

The rpm's should be about 5300-5500 at wide open.

This can be affected by all the things listed by me and pnwboat.
You can change the things above or change the prop to a lower pitch and that will increase your rpm's.

 

[glennkil]

Pnwboat and Jerry, thanks for the info. I am getting to those items regarding weight and prop pitch. Had boat out on water other night and wasn't that keen to lean over back of boat with cowl off and the thing screaming in my face with flywheel inches from it. Keen to know where you check for full throttle opening with engine off? By manipulating the throttle at the engine OR by pushing throttle at forward controls fully forward? Does the full throttle position change with the engine running by anything moving? I read on another post that a 50 will run perfectly fine on one cylinder but seem down on power. How true is that? If I disconnect a plug lead and try to start it do I need to short the lead out to protect the electronics? If I remove a plug lead while its running with my hands will I get belted?

 

[jerryjerry05]

The 50 can run ok on 1 plug but you won't get 4200.
Start it and pull the plug wires off one at a time.

The throttle should be able to open the carb all the way when pushed forward.
This can be done not running but the prop needs to be turned a bit when shifting into gear.
Otherwise the linkage can bind and even break.
When in F and all the way forward, push the throttle cam/roller further and see if it goes past where it's set.

 

[glennkil]

Jerry the plate only opens to about 75% horizontal. So do I lengthen the rod to allow full throttle to be achieved? Will this lift the idle speed though and will I need to back that adjustment off. Whatever I do I don't want to stuff up the gear selection adjustment because that was seriously painful to get correct. There is very little movement between forward, neutral and reverse and half a turn on the rod can make or break the selection.

 

[Nordin]

Glenn .... set the remote in WOT, hook off the throttle rod at ball joint (be careful not breaking the plastic part).
Length the rod soo the butterfly open up to horizontal.
Shift remote to neutral and then WOT again.
Check the butterfly..

 

[jerryjerry05]

The butterfly doesn't necessarily have to be level/flat to be at wide open.
Sometimes it goes past level and others it doesn't.

Top three posts have tip on making these run better.
Find the link and sink one and see if that can help.