1979 140 Mercury sitting for years

[Rhoss]

Hi. New to boating and new to two cycle motors. My question is: with the spark plugs out turning motor with wrench I get multiple resistance that feels like compression. Not sure if I'm being clear but as I turn the motor it is easy and then tight. Repeat, repeat......Is this normal or do I have an issue?
Thank you for any help you can give me.

 

[jimmbo]

Welcome to iboats

There is crankcase compression(needed to transfer air-fuel mix to combustion chamber), that is probably what you are feeling

 

[Rhoss]

Thank you. That leads to my next question. The boat battery is dead so I put my shop charger on it but when I install the plugs it struggles to barely turn over. I tried jumping it from my running truck with no difference. Will I need to invest in a new battery just to see if it will start?

 

[jimmbo]

Will I need to invest in a new battery just to see if it will start?

If the battery is bad. However, the problem may be corrosion/poor connections. Clean and tighten all connections. You may have an internally corroded cable. If you have a voltmeter, do some basic voltage drop tests. If not, try bypassing the solenoid. Just beware of Polarity. Also sparks, beware of them near gas and batteries

 

[Rhoss]

I bypassed the solenoid and the motor started. Now I'm not afraid of spending money on needed items as its not a lost cause. This motor had sat for over 10 years! As a point of interest I used SeaFoam Deep Creep to free it up before trying to start the motor.
Thank you very much for your generous and accurate advice, I appreciate it.

 

[jimmbo]

First thing then to spend money on is a new water pump impeller.

 

[Rhoss]

That is number one on my list. Any other items you would suggest?
I'm using a 3 gal portable tank with new hose and bulb to bypass the inboard fuel tank and fuel lines while testing.

 

[jimmbo]

What condition was the oil in the gearcase? Clear amber, dark, or something looking like coffee with cream? Get rid of any old fuel in the tank. Fuel mix, use TCW-3 oil mixed 50:1

Never run the engine out of the water, unless in a tank with the waterpump submerged or on the a set of muffs. It only takes a few seconds to destroy the impeller.

 

[Watermann]

Weak battery and worn out starter will definitely make for a struggle to turn the motor over. That 79 should have a rope coil for hand starting on the flywheel, give a mighty tug and see how well she spins.