3.9 merc not run in 30 years

[burchdog]

I have my dad's old 3.9 merc in the barn. It has not been run in 30 years. I would like to give a try at starting it up and using it next summer but I am afraid to just fuel it up and crank on it. Is there some place that I can find a guide to help me with a proper technique so I don't just ruin the motor. I do know that the motor ran well when it was last used with no issues. I would like to do this my self to save money unless you guys think it is best if I take it to a professional. I have pretty good auto mechanical abilities, tools and work space.

 

[Bob_VT]

Re: 3.9 merc not run in 30 years

Welcome to iboats...

Read this as a start http://forums.iboats.com/showthread.php?t=158086

 

[Sea Rider]

Re: 3.9 merc not run in 30 years

Remove plug, raise engine horizontally to have piston at a vertical position squirt a good oil dose inside to be evenly distributed around piston & cylinder wall, pull rope, is engine seized ? if so you are probably done or will have 70% more work. if not, much better, check spare parts availability : impeller or complete WP kit, carb kit, pump diaphragams for such old model engine if planning using it for summer.

Happy Boating

 

[M9.9]

Re: 3.9 merc not run in 30 years

Hi Burchdog and all,

LAST RESORT TRICK: There's a little trick to freeing up an stiff engine (wont turn over with using pull start) but I have never tried it and your probably not going to find it listed in a repair book.

Remove the engine cover and pull start assembly exposing the the center flywheel nut. Support the bottom of the engine with a block or two of wood so that the engine is supported from the ground up. using a BRASS DOWEL (Not Steel) and a hammer, preferably a 5lb hand-sledge.
Centre the BRASS DOWEL on the top flywheel stud and give it one good whack. Be sure to go through the lubricating process FIRST as it may free things up enough. The Brass Dowel trick is uesd as a last resort as it should free-up the crank. If you use a Steel Dowel, the stud might mushroom and then you have a problem. If you use wood it will buffer the intended effect and may not do the job.

 

[burchdog]

Re: 3.9 merc not run in 30 years

Thanks to the three of you for your information. That is just what I needed and I appreciate your time. I tried to find this type of info by searching and looking at FAQs but never did, I have a lot to learn about using a forum. I will buy a good manual after I determine the engine is not seized and get going. If the engine is not seized this should be a fun winter project. Keep warm guys.