Logo
FULL SITE MENU

little trouble with a 70 horse

C

coryv4

New member
i have a 1975 evinrude 70 horse 3 cylinder. it start runs and idles out of water with muffs on, but when its in water it will not stay running. to start it in water you have to flip the warm up switch and choke it then remove the choke. it will idle for a few seconds then die. if you try to put in in gear it immediately dies. all 3 cylinders have 145psi carbs are clean all the wires are good. like i said out of water the motor doesnt misses a beat. by the way, im new to the site and am looking forward to some good info.


thank you.
 
Hopefully it is a very LEAN adjusment of the idle mixture screw with a TOO SLOW idle speed. That is usually the result of setting them up on a trailer.

Resetting the idle mixture slightly RICHER & possibly a faster idle speed makes the engine a rock solid runner. Try It

I can adjust my motor so slow on a trailer, that I can feel each pulse of power very slowly. It will die everytime I shift it in the water.
 
If you have no idle mixture screws. Raise the idle speed so that when shifting in the water. You get a soft mechanical clunk as you go into gear. A soft clunk will not destroy the gears.

If that still causes stalling. Post back.
 
i tried raising the idle to even to what i think "i own alot of 2 strokes sleds and atvs" sounds about 3k rpm and it still idles for a few seconds in water and it will die immediatly when putting it in gear reverse or forward. i should add this, the engine seized 5 years ago and with a little 2 stoke oil dumped in it freed up so it wasnt a bad seize. my cousins were using it and it locked up on them they didnt have much to say so i dont know if it cold seized from not letting it warm up or if they were running it wide open all day. but like i said it has 145 psi in all cylinders.
 
Does spark jump a 7/16" gap on all 3 ??---------That is the only test result for spark that is acceptable in my book.---------Has the flywheel key been checked ??
 
racerone said:
Does spark jump a 7/16" gap on all 3 ??---------That is the only test result for spark that is acceptable in my book.---------Has the flywheel key been checked ??
Click to expand...

i will check spark gap and fly wheel and get back with you guys. is there an adjustable timing on this motor that could possibly have moved?
 
The timing on these motors is fixed at the factory.----Really should not need adjusting for the life of the motor.-------But then again owners do start adjusting / guessing and make mistakes by making adjustments.-----They often do this with the hope that it will magically run better.
 
A seized engine is SUPER HOT and cooks anything mounted to it. Done 2 times ?

Racerone
How about a severly overheated fuel pump mounted on the engine ? Diaphram & those tiny rubber check valves. When I remove those tiny check valves some just pull apart.
 
cyclops2 said:
A seized engine is SUPER HOT and cooks anything mounted to it. Done 2 times ?

Racerone
How about a severly overheated fuel pump mounted on the engine ? Diaphram & those tiny rubber check valves. When I remove those tiny check valves some just pull apart.
Click to expand...

seized only once. i dont know what i did but i was messing with some random stuff pulled the fuel pump off it was clean put it back on backed it in some water and now it seems too work. tomorrow i am going to launch it and have a boat follow me just in case.maybe when i pulled it apart clog fell out or somthing.
 
coryv4 said:
im pulling the motor and doing a leak down. im suspecting an air leak or maybe even water leaking in the motor.
Click to expand...
That's a very good guess. If it seized from overheating, it has warped the exhaust cover baffle plate, allowing water to squirt into the exhaust ports. That is a common thing with overheated 3 cylinder loopers. Besides that, it may have (probably) scored some piston skirts, which affects crankcase compression. Short end of the story is the motor is sick, not running equally on all 3 cylinders. I've given a couple of possible scenarios, now you have to do some troubleshooting and find out what it really is.
 
fdrgator said:
That's a very good guess. If it seized from overheating, it has warped the exhaust cover baffle plate, allowing water to squirt into the exhaust ports. That is a common thing with overheated 3 cylinder loopers. Besides that, it may have (probably) scored some piston skirts, which affects crankcase compression. Short end of the story is the motor is sick, not running equally on all 3 cylinders. I've given a couple of possible scenarios, now you have to do some troubleshooting and find out what it really is.
Click to expand...

i pulled the exhaust cover off and shined one of the cameras in there and they is no scoring or scratches. all the cylinders sounded like they were running evenly and all the plugs were dry.
 
bumping an old thread. all cylders are prime. crank bearings and what not are all good. i did a leak down not a single air leak. carbs had a acid bath and everything adjusted by the book. and still the same problem.
 
Back
Top