1984 Rude 6hp runs great at idle but stalls when twist throttle

[catfishin_welder]

New plugs, new fuel line, fittings, primer bulb. Starts on 1st pull, runs perfect at idle but stalls when throttle opened up. I'm thinking maybe fuel pump diaphragm bad and not forcing fuel to carb fast enough?? If i prime carb then remove fuel line from pump to carb, start motor, twist throttle and watch for fuel flow to increase, is this proper way to troubleshoot fuel pump? Also thinking i may clean carbs top to bottom. Thanks for any input

 

[Bosunsmate]

Re: 1984 Rude 6hp runs great at idle but stalls when twist throttle

You could try that or try manually priming with bulb to act as a surrogate pump yourself.
If it stalls when you apply throttle id say the fuel bowl would still be full, maybe the extra pressure is flooding her.
Does the primer bulb hold firm with engine off?

 

[Vic.S]

Re: 1984 Rude 6hp runs great at idle but stalls when twist throttle

New plugs, new fuel line, fittings, primer bulb. Starts on 1st pull, runs perfect at idle but stalls when throttle opened up. I'm thinking maybe fuel pump diaphragm bad and not forcing fuel to carb fast enough?? If i prime carb then remove fuel line from pump to carb, start motor, twist throttle and watch for fuel flow to increase, is this proper way to troubleshoot fuel pump? Also thinking i may clean carbs top to bottom. Thanks for any input

I have the same engine. ( well at least a 6hp yachtwin)

If it stalls as soon as you open the throttle but otherwise would continue to idle happily I would think mostly likely that you will have to clean the carb.

If it dies slowly I'd suspect a fuel flow or pump problem.
Worth gently pumping the primer bulb as suggested to see if that will keep it going .. if does then very possibly it is the pump at fault.

My engine on my little sailboat:

 

[catfishin_welder]

Re: 1984 Rude 6hp runs great at idle but stalls when twist throttle

@ Bosuns...unsure of firmness of bulb haven't actually checked it. @ Vic...i believe the bowl may be full also as i can disconnect fuel line and motor will continue to run and yes same motor w shorter shaft. Are you guys suggesting that with motor running, I open up throttle and then pump bulb to see if pumps keeping up? I've had motor since new, very few hours on it but I've had it in dry storage for past 3 yrs. I always ran it dry on fuel before pulling out of water and fogged cylinders before putting it away for winter. I was concerned that diaphragm may have dry rotted or carb gummed
. I appreciate your replies!

 

[nwcove]

Re: 1984 Rude 6hp runs great at idle but stalls when twist throttle

has the carb ever been overhauled? you may be pleasantly surprised what a proper cleaning/rekit will do.

 

[Vic.S]

Re: 1984 Rude 6hp runs great at idle but stalls when twist throttle

Are you guys suggesting that with motor running, I open up throttle and then pump bulb

Yes . If the fuel pump is not working then gently squeezing the bulb should keep the bowl full and the engine should run OK

There are no OEM parts for the pump but aftermarket repair kits are available ( Sierra ??)

Rebuilding instructions at Rebuilding the OMC Fuel Pump


The real clue though will be whether or not the engine stalls as soon as you open the throttle. If it speeds up, runs briefly, then dies the problem is almost certainly a fuel supply one. If it stalls immediately or if pumping the bulb wont keep it going it is more likely to be a blocked main jet in the carb.

I guess the effects of ethanol in the fuel on diaphragms and hoses is something you have to be aware of ........ an evil still to hit us in the UK

 

[catfishin_welder]

Re: 1984 Rude 6hp runs great at idle but stalls when twist throttle

It stalls immediately but continues to run fine when i twist throttle back to slow

 

[the machinist]

Re: 1984 Rude 6hp runs great at idle but stalls when twist throttle

Is there a possibility that your throttle linkage to the timing plate is disconnected?