1975 Rude 50 hp will not stay running at Idle...... UPDATED

[rentprop1]

almost everything on this engine has been replaced except the rectifier and the coils, it will start right away using the warm up lever, when the warm up lever is lowered slightly after 3-4 min, it runs so rough it almost stalls, if I lower the lever all the way to engage the prop it almost dies, but will go into gear and run, but even rougher till about 1200 rpm's then its almost perfect, will run for about 4 min then just die.....will be very hard to start , but will re start under the above conditions.....once or twice more,,,then will not start for about 30 min......
.........new impeller and good water flow, medium amount of white smoke from the oil mix....fuel is new/ no ethanol properly mixed, no chance of bad gas, fuel system was checked and lower carb opened up just slightly....the shop had it running fine for 10-15 min in the test tank, but at home in the tank or at the ramp dies like above.

also mechanic said I should not use the ears to run this motor at home, whats up with that ??

 

[tashasdaddy]

Re: 1975 Rude 50 hp will not stay running at Idle

Re: 1975 Rude 50 hp will not stay running at Idle

they do not like muffs. check you compression and spark on both cylinders, when the motor is cold, and right after it shuts down. read the single needle carb adjustments, in the TOP SECRET file, top of forum.

 

[wayne h]

Re: 1975 Rude 50 hp will not stay running at Idle

Re: 1975 Rude 50 hp will not stay running at Idle

i agree with running a compression test on the motor .its the first step of a tune up that no one ever does . if you have compression and spark the only other thing can be fuel .what plugs are you running ? Champion L77JC4 or QL77JC4 plugs set at .040 . The original plugs were Champion UL77V plugs but they have no heat range and are subject to fouling. i would bet that one of the carbs is fouled . have you tried to pull a plug wire off on one of the cylinders and run the engine at idle to see what carb might be the problem .

 

[a70eliminator]

Re: 1975 Rude 50 hp will not stay running at Idle

Re: 1975 Rude 50 hp will not stay running at Idle

I may be all washed up here but here goes.. you say it smooths out at above 1200R's but won't idle, to me it sounds like you low speed adjustment is too lean or too rich either way your engine will not idle, it will just spit and spat a couple times and die if too lean, or it will just plain load up and die if its too fat, and foul your plugs too. At the 1200 and above range your into the high speed jets and out of idle circuit. This is just my thinking. Have you played with the low speed adjusters?

 

[rentprop1]

Re: 1975 Rude 50 hp will not stay running at Idle

Re: 1975 Rude 50 hp will not stay running at Idle

my son said back when they checked it, the comp was 137 and real close on the other cyl........

after the 3 restart attempt thats when the spark would disappear for about 30 min then re-appear

 

[rentprop1]

Re: 1975 Rude 50 hp will not stay running at Idle

Re: 1975 Rude 50 hp will not stay running at Idle

ok today we messed around with the motor, I think the problem is with the advance to start lever ( warm up lever )....when you first start the boat the lever is used and the motor usually fires after about 4-6 seconds of cranking, after letting it warm up 3-4 min, when you lower the lever back to the normal idle is where the engine starts to run really rough and finally dies.

could the issue be with the adjustment in the control box ( throttle ), or at the engine, is there proper way to adjust that warm up lever ?

where do I start, the carbs or the lever ??? I really lost here........thanks

 

[tashasdaddy]

Re: 1975 Rude 50 hp will not stay running at Idle

Re: 1975 Rude 50 hp will not stay running at Idle

sounds like contaminated carbs. have you replaced all the fuel lines with alcohol resistant fuel lines? read the TOP SECRET FILE.