1971 mercury 500 50hp dies when put in gear!

doughboy19 · Mar 28, 2009

I have rebuilt the carbs, adjusted the floats, rebuilt the fuel pump, the reeds looked fine(from what I could see when cards were off), have 115 psi on all cylinders (4 cylinder), have great spark on all the new plugs, all wiring has been replaced, motor idles almost perfectly, no tach

. When ran with ear muffs on shifts in to gear runs and revs fine. But when set in water dies after put in gear either direction. Throttle and shift cables have a little play in them. I have a manual on the motor, but need some help!???? Any ideals?

Yepblaze · Mar 28, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

Tie the boat off to the dock, and adjust it on the water. In and out of gear.

doughboy19 · Mar 28, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

Thanks for the quick reply, I tried to but no matter what still goes dead when put in gear and cannot start with in gear due to neutral saftey switch. If I idle up it grinds into gear.

Yepblaze · Mar 28, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

Are you adjusting the idle mixture screws?

Are they responding as would be expected?

quillKing · Mar 28, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

hey doughboy-I have the same EXACT symptoms. runs great with the muffs-high idle, forward, reverse. but i drop it in the water, put it in gear and kills. you've tried everything i was thinking of doing. lot of knowledge out there and i bet sooner or later someone will help you out. i'll be watching your post.
good luck!

doughboy19 · Mar 29, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

idle screws are working just fine stumble one way then stumble other way just in between. I tried to retard the distributor just 1 notch and seemed to miss a little but without throttle and shift cables attached I could put in gear and would run, but i don't think timing is correct that way and I dont wont to mess up the motor(sputtering).

doughboy19 · Mar 29, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

I did notice with the throttle and shift cables on the fast idle throttle had to be moved half way up before any movement. Do these cables stretch out over time? Could this possibly be my problem? And why would I have to make the engine sputter before it will pull, instead of making it idle right? Please help?

potterp · Mar 31, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

Don't know much about outboards but I had the same problem with my 4.3L V6 mercruiser. It was because of the shift cable being stretched. When an I/O kicks into gear it kills half the cylinders so the load isn't too hard on the engine. With the cable stretched it wouldn't kick in quick enough so it would die everytime I put into gear. Had to get a new cable.
Not sure if outboards do the same but I thought I would mention my senario.

doughboy19 · Apr 2, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

potterp thanks for the input. It does make alot of since. Someone told me that I might have too much slack between when it shifts into gear and when then primary pickup starts moving thus dead engine. I'm going to get new cables.

CharlieB · Apr 3, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

Merc did not use an ignition interrupter on their outboards. New cables will not cure your problem. It is normal for the throttle to advance timing a little before the carb linkage begins to move.

Idle mixture is still too lean. On the hose adjustment to best idle, halfway between the lean and rich stumbles, is still almost 1/4 turn too lean for when the motor is put into the water. Back the idle mixture screws OUT 1/4 turn,it should then idle in the water.

Once in the water, readjust idle mixture to best idle while IN forward gear. Test acceleration in gear, any bog or hesitation then further richen/open idle mixture screws an additional screwdriver blade slot width and retest. Repeat as necessary until ALL signs of bog or hesitation is gone.

cubic123 · Apr 3, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

Had the same problem with my 115 HP Merc .Marina set the idle .Problem is the muffs cannot duplicate the load as in a lake so they had to guess a little and adjust .Fixed the problem .

doughboy19 · Apr 12, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

Thanks for the replies. I have found by the good advice to richen the carb and guess what it works but know the problem is lose of power at top end kinda sounds and feels like it floods or bogs down untill i let off the throttle. But if i lean up it will not idle in gear. So win and lose I guess! Any more advice? Yall are hot and on the right track keep'em comin'.

CharlieB · Apr 17, 2009

Re: 1971 mercury 500 50hp dies when put in gear!

A lost of power at WOT can be a weak fuel pump or a dirty main jet.

Continued operation of a lean motor WILL MELT A PISTON.

Test by squeezing the primer bulb to increase fuel pressure, if the fuel pump is weak the engine will pick up. If so rebuild the pump.

If NOT, then rebuild the carbs, make SURE the jets and all passages are clear and CLEAN.

1971 mercury 500 50hp dies when put in gear!

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