Mid-seventies Mercury 850 won't turn over with plugs in

[dabuilderman]

Hi, this just got this unit after sitting for 2 years. The friend who owned it last says it ran perfect last time he had
it out and he did nothing to modify timing, etc since then. It has decent compression (over 100 in all 4 cylinders)
I first removed spark plugs, sprayed lube in cylinders and let it soak in. Starter turns over nicely with plugs out with
10A current from a rolling battery charger. After re-installing spark plugs it is super-tough to turn over, even on 200A
boost setting on charger. It moves only a fraction of a revolution every time. Any ideas ??

 

[racerone]

Take starter apart for inspection.----Ohm test on armature.

 

[dabuilderman]

OK, so you are thinking weak starter ? thank-you RR

 

[dabuilderman]

All armature tests passed, but large piece of magnet broken off. I am guessing this is not good.

 

[racerone]

In the old days people used to tap a starter to possibly free up stuck brushes.----Starters like yours say ---" do not hit with a hard object " -----But people ignore that or drop starter on the floor.----Your location ?----Many shops might have starters in a bin and you might score an assembly with good magnets.----Or scour the internet for a cheap replacement from offshore.----An easy fix for me here.

 

[dabuilderman]

I just ordered a new 1 for $108. not bad. thanks !

 

[racerone]

At that price it is hard to go wrong.---But I would find an assembly with good magnets here under the work bench.

 

[dabuilderman]

New starter installed. Problem is still the same.

 

[dabuilderman]

Starting to think maybe plugged exhaust manifold. So much pressure

 

[faztbullet]

You trying this with a battery or just charger?

 

[dabuilderman]

Rolling charger, even at 200A boost no go

 

[faztbullet]

Need a battery