70 horse sat for two years...what should I do first

[Swivelhart]

I am buying a boat with a 1977 (I think its pretty close in year) 70hp Johnson. It has sat for two years but was running great when parked. I am buying it from a 75 year old man. Anyway, are there any precautions I should take before attempting to start it. Do I need to squirt stuff in cylinders first or is that only if its been like a decade? Also are there any issues that can occur from sitting this long aside from nasty fuel related stuff?

 

[fireman57]

Re: 70 horse sat for two years...what should I do first

I don't believe that is a '77 it looks more like and early '70 model that had the selectric shift which required a part in the lower unit that would shift the gears electrically. They are getting harder to fine. If I bought this engine I would rebuild the carbs and put a water pump in it. Also change the lower unit oil. Do not buy it until youdo a compression test on it. The numbers should be within 10% of each other and preferable above 90.

 

[hidef]

Re: 70 horse sat for two years...what should I do first

It is a 1976 to be exact. You can go to the top secret files and read how to wake a sleeping outboard. I would replace all of the fuel lines with alcohol resistant lines as well as changing out the water pump.

 

[James R]

Re: 70 horse sat for two years...what should I do first

Shoot a mix of Marvel mystery oil and 2 stroke oil in the plug holes and tilt the engine up. Rotate the crankshaft with a wrench on the flywheel nut and let soak over night. Next day open the throttles and shoot the same mix into each of the carb throats whilst turning the engine over with the starter. Leave to soak again.
Next do a compression check. All cylinders should be in excess of 100PSI and within 10% of each other. while you do this you can do a provisional check on the sparks. Connect a piece of solid copper wire to a good ground and twist around the threads each of the plugs to ground them. Plug the plugs into the wires and look for spark when turning the motor over. Get someone to turn the key while you watch. If all looks good then strip, clean and rebuild the carbs.
With all this done the lower unit will need to be pulled and the pump impeller and oil will need to be changed.
Replacing fuel lines is also essential along with cleaning of fuel tanks. If you have a steel fuel tank get rid of it. Rust and dirt will do a number on your nice clean carbs.
Good luck on your project and keep us informed.

 

[jay_merrill]

Re: 70 horse sat for two years...what should I do first

Middle 70s looks about right. There should be a data plate on the port side of the transom mount. It will say something like "70EL76D," if it is a 76.

The motor looks like it has a tilt tube for the steering, plus it appears to be a 70hp motor, so it shouldn't have hydro-electric shift. That system ended in the 3 cylinder motors, with the 65hp motor of 1972.

Those motors were pretty well known for having compression values of up to about 150 psi, so ideally you should be seeing 130 psi or better. If the motor was well taken care of, you just may see such values. I agree with the 10-15% rule on differential and the motor should run OK with compression of about 90-100 psi or better, as long as the differentials are within tolerance.

Do the "waking an old motor" routine and enjoy - the OMC triples are great engines!

 

[Swivelhart]

Re: 70 horse sat for two years...what should I do first

Shot the cylinders with some junk and let it sit a day...turned the key with the warm up engine lever up a little and choked it...within seconds she fired right up (actually revved a little higher than desired but put the warm up lever back down quick) and idled beautifully.

 

[hidef]

Re: 70 horse sat for two years...what should I do first

It is hard to kill the old OMCs now just do all the recommended maintenance and that thing should run for years.

 

[James R]

Re: 70 horse sat for two years...what should I do first

Now don't forget what we said. You will need to dismantle the carbs and soak them in Gunk Carb and parts cleaner. Don't use the spray cleaners as they can damage your carb parts. Follow the instructions on the can. Why clean and rebuild with new kits? Because if you don't you can burn out a cylinder through poor lubrication. While you are doing this replace the fuel lines with new, for ethanol use, lines. Rebuilding the fuel pump doesn't cost much and can save some trouble down the road. Also change the oil in the lower unit and replace the water pump impeller. Impeller failure can result in a seized motor in the middle of the pond. Not a pretty sight.
Always use Stabil in your fuel to help keep those nice clean carbs clean.
Good luck and hope you have many happy hours out of your motor as we do ours.