1981 Evinrude 70 hp

[Dave64]

When I tried this motor out it ran find. Got it home put the muffs on it and it over revved at idle throttle, I turned the key off when it got to 4,000 rpm.
Noticed it wasn't pummping water. Put new water pump housing and impellar in. Now it's pumping a good stream. Runs good in the drive-way with the muffs on and idles find. I don't think this motor was used very much in the past six years, and proably wasn't winterized. I put a can of Sea Foam in the gas tank and took it to the lake. I got it away from the ramp and out in the lake and it seemed to be running fine so I opened it up and top end was about
2,000 rpm. Did the Sea Foam break so much dirt loose??? Should my next move be to take the carbs off andf clean everything???? Also I can't get it to idle when in the water. Any information would be appreciated.
Thanks

 

[Daviet]

Re: 1981 Evinrude 70 hp

Start with a compression and spark test, those engines would run great on two cylinders while on the hose. If spark and compression are ok, you are probably going to need to overhaul the carbs.

 

[jtexas]

Re: 1981 Evinrude 70 hp

seafoam is good stuff but it won't clean a dirty carb; for that it has to be disassembled.

Here's a couple recent examples of the dangers of revving an outboard motor on the muffs:
http://forums.iboats.com/showthread.php?t=430070
http://forums.iboats.com/showthread.php?p=2871136

 

[Dave64]

Re: 1981 Evinrude 70 hp

Thanks for the info. Compression was 90 to 95 and the spark looked good. Should I get carb kits and rebluid while I got them off?
Thanks again,

 

[kenmyfam]

Re: 1981 Evinrude 70 hp

No harm whatsoever in giving the carb's a service. It can only help and if not been done for a while with untreated gas in there you may be surprised at what you find in there.

 

[Dave64]

Re: 1981 Evinrude 70 hp

The compression was 90 to 95 and the spark was good. I don't really know what the compression should be. Is that good? If I take the carbs off should I rebuild while I got them Off?

 

[eavega]

Re: 1981 Evinrude 70 hp

Was it 90-95 on all three cylinders? If so, your numbers should be good (actual reading seems a bit low, but you can always chalk that up to the tester or technique as long as they are within 10%). Your next step would be to tear down, clean, rebuild carbs, then link-n-synch. If it is a clogged jet that should solve your RPM issues as well as your poor idle issues.

Rgds

E

 

[jtexas]

Re: 1981 Evinrude 70 hp

agree, on that vintage I would look for upwards of 110, but all 3 between 90 & 95 should be ok. Once you have the carbs off the motor, it only makes sense to install the kits, about $12 apiece on iboats. Follow the "carb cleaning and rebuilding" link from the "top secret file" at the top of this forum.