1976 70hp evirude"2000"rmp only?

[eric65]

i have recently purchased a small boat with a 70 hp evinrude and cannot get to more then 2000 rpm while underload. it will rev great while not under load, but while running in lake can only go about 10mph. any ideas where to start?

 

[cdoliver]

Re: 1976 70hp evirude"2000"rmp only?

a new-to-me engine I would
1. check compression
2. clean/rebuild carbs
3. change plugs using the correct reccomended ones
4. change lower unit fluid
5. check spark
6. change water pump
7. decarb

most likely you have a gummed up carb if it has set for any amount of time

 

[eric65]

Re: 1976 70hp evirude"2000"rmp only?

ok will do thank you. i have replaced plugs, and checked lower unit fluids. the motor has lots of power, just wont go over 2000 rpm. is there some kind of restrictor or rev limiter that im not finding?

 

[red10]

Re: 1976 70hp evirude"2000"rmp only?

i have a 1975 70 hp evinrude and being that old the coils develop cracks and start arcing so my guess is you have a bad coil, had same issue with 50 johnson, running on 1 cylinder wouldn't go over 7 mph. An easy way to check if its arcing would be to leave the hood off and fire it up at night and look for the pretty blue light.

 

[countvlad]

Re: 1976 70hp evirude"2000"rmp only?

i have recently purchased a small boat with a 70 hp evinrude and cannot get to more then 2000 rpm while underload. it will rev great while not under load, but while running in lake can only go about 10mph. any ideas where to start?

theres no doubt in my mind the high flow jets are clogged up... i would either try to do a decarb, which might be too late, or definetly rebuild the carbs....

http://forums.iboats.com/showthread.php?t=158076

when was last time that there was a decarb done or carbs rebuild? exactly i thought so... keep us updated good luck