1973 50hp Merc starts to bog down

[itchystarfish]

Hi all. I have a wierd problem that hopefully someone out there with experiance can point me in the right direction.<br /><br />I just purchased an older 14' K&C boat with a 1973 50 hp merc 500 with a thunderbolt ignition?. <br /><br />The previous owner told me he replaced the timing belt and he couldn't get it going. I picked up a manual and noticed that the arrows on the flywheel/mag didn't line up so I lined them up and behold she came to life.<br /><br />Now, here's my problem.<br /><br />The motor starts great, idles great, goes into forward/ reverse gear (merc control box)no problem, I give it gas and it's slow out of the hole (engine is smooth though, no hickups)and then at half throttle it starts to bog down.<br />I checked for fuel/ gaskt leaks and cleaned out all the lines and screens. Nothing changed even pumped the ball to see if it was starving for fuel,nothing. <br /><br />With the engine in nutral i lifted up the inside small lever on the control box, the motor has excellent response, revs out good too, I lower the lever all the way down and it idles nice, put it in gear and as stated above it's slow out of the hole and gags at half throttle.<br /><br />I don't think it is ignition/timing because it starts/idles real nice.<br /><br />I don't think it is the carbs because in nutral using the inside lever she revs nice and tops out real nice (no tach) but it is smooth.<br /><br />Could it be that the carb/mag needs to be syncronized? If so in the manual it says to retard the ignition driver, ignition driver is that the mag? and is retard left or right? <br /><br />When hooking up a hand held tach where do I attach the two leads too? <br /><br />Also I should mention the control box has some slack in it, when pushing the lever forward it goes about 15 Deg. before the throttle begins to engage. Could this all be a linkage problem needing an adjustment?<br /><br />Any help would be greatly appretiated.

 

[merc_500]

Re: 1973 50hp Merc starts to bog down

Hey itchy, i have the exact same motor as you only a '74. <br /><br />First off, sounds like you got timing set correctly. <br /><br />Second, the shift lever is supposed to have that slack in it. Mine does as well. <br /><br />What happens when you push the throttle past half when in gear? Does the motor start to rev up but not go anywhere? If thats the case then sounds like your prop is slipping.<br /><br />Does it start to chug and shake and want to stall until u slow it back down again? Than it sounds like a dirty carb. <br /><br />have u removed, cleaned and dissasembled both carbeurators? <br /><br />Do both cylinders have good spark, compression? <br /><br />Proper fuel ratio of 50:1? <br /><br />Let us know what u find.

 

[Barnacle_Bill]

Re: 1973 50hp Merc starts to bog down

Something to consider. I recently read a long thread about someone with the same problem. He had replaced everything on the motor and still had the problem. It turned out that his exhaust passage was nearly clogged closed. He was able to clear it by dropping the lower unit and digging the crud out of the bottom of the motor.