1978 70hp seems seized - can I free it?

[suzukidave]

Have just acquired a boat with a '78 70hp merc that has been sitting for 6 years or so but "ran good" before then (sure it did ). Paid nothing for the motor but would like to get it going if possible. Throttle cable seems to work well and I can find neutral ok but I can't turn the flywheel with the rope start and haven't tried the starter as it has no battery. Starter teeth are not engaged and I can't see anything else blocking the flywheel from turning. I am assuming it is seized, unless it is normal for these things to be impossible to move with the rope. Given it won't turn at all by hand I am worried about applying the starter motor to it in case it can be saved. Is there anything I could put in there that could free it up or that might make the start up less traumatic if it does turn over(oil, liquid wrench, fogging oil etc...?).

 

[phatmanmike]

Re: 1978 70hp seems seized - can I free it?

hi suzuki dave.... i have heard of people pouring oil into the carb throat and also into the spark plu holes and tilting the engine around to various angles to spread the oil.<br /><br />try taking the plugs out , maybe it will relieve some cylinder pressure a lil, who knows...<br /><br />does the prop spin, you say you can find nuetral ok... but im not sure what you mean...<br /><br />try some of these and let us know..<br /><br />m ikey

 

[jim dozier]

Re: 1978 70hp seems seized - can I free it?

You've got nothing to lose by taking the spark plugs out and filling the engine with penetrating oil and letting it sit awhile. Put a breaker bar socket wrench on the flywheel nut to turn it slowly. If you can loosen it up it may run but there is no telling how deep a groove may have rusted in the cylinders unless you take it apart. If you get it turning you could do a compression test to see if its worth fooling with.

 

[suzukidave]

Re: 1978 70hp seems seized - can I free it?

By "I can find neutral" I meant that I had confirmed I was not stuck in gear. The prop turns in neutral both ways and one way in gear with a click. I will try liquid wrench from all directions and a breaker bar. I know it may be a lost cause but if I can free it up I would at least know it is the cylinder not the crank.<br /><br />The lower end feels fine but maybe I will drop it down to make sure that's not the problem.

 

[Chris1956]

Re: 1978 70hp seems seized - can I free it?

Dave, It is possible that the drive shaft is seized in the lower gearbox. Also, if you do repair it you will want to replace the impeller anyway, so drop the lower unit. Now if the motor still doesn't turn, oil it up well. If that doesn't do it, pull the transfer covers and look at the cylinders. This should "tell" you which one (or all) are rusted. Then put a brass rod through the spark plug hole and tap the top of the piston. Tap firmly and it should break loose. I think this is better than using a breaker bar since if you guess which piston is seized, there is no strain on the crank, rods, bearings etc. Good luck<br /><br />PS you may be able to inspect the cylinders thru the transfer ports, and know what needs attention.

 

[suzukidave]

Re: 1978 70hp seems seized - can I free it?

Chris, thanks. A brass drift tapping the cylinders through the plug holes is a great idea but what are the transfer ports exactly and how do I remove them?? <br /><br />Also, I will do a search but is there any trick to dropping the lower unit on these? It's dead simple on my Suzuki which is all I know.

 

[Chris1956]

Re: 1978 70hp seems seized - can I free it?

Dave, To drop the LU, put the motor in neutral, and remove five locknuts(visible) and a bolt hidden under the zinc tab behind the prop. You will need to remove the bolt that holds the zinc through the hole in the midsection(1/2" socket and extension), above the prop.<br /><br />The transfer covers are on the starboard side of the motor. They are usually ribbed, verses the smooth water jacket covers. The usually have (up to 8) 1/4-20 SAE bolts holding them to the block.

 

[suzukidave]

Re: 1978 70hp seems seized - can I free it?

ok, penetrating oil did not free it up at all so I pulled the transfer plate. The top cylinder is obviously rusty and toast. It is on the upstroke and I can see in behind that piston arm etc is heavily coated in rust. The middle cylinder is fine. The bottom has a small amount of rusty looking grit deposit in the port area but I can't tell if it bad or not because it is on the downstroke and so I can only just see the head. I tried a brass drift through the plug holes on the top cylinder but could not free things up.<br /><br />I am thinking with all the visible rust in behind the cylinder there is a good chance of crank damage? It therefore seems to me I am better off to go for an exchange power head than to get this thing rebuilt locally. I will post separately on that.

 

[Gold Bear]

Re: 1978 70hp seems seized - can I free it?

suzukidave <br /> <br />Sounds like the exhaust cover was leaking before the engine was laid up, resulting in the rust you see. <br /><br />One bit of advice, if you are using a brass drift bar, be sure the piston crown is near the middle of the bore (not near the top or the bottom) because there is relatively little up and down travel as the crankshaft throw goes around, and striking the piston is going to put severe pressure on the piston, rod, bearings and crank.<br /><br />It sounds like it's time for a tear down.<br /><br />Good Luck,<br /><br />Gold Bear

 

[suzukidave]

Re: 1978 70hp seems seized - can I free it?

thanks gold bear. hopefully the rust absorbed the strain from the tapping . I am leaning towards a powerhead swap so someone else can do the tear down.