81 70hp merc

[Barry&Lori]

> How much to rebuild a 1981 3 cyl Merc O/B ? Providing there isnt any<br />> internal scoring beyond normal wear and tear ?<br />><br />> What happened : Buddy and I just got his boat in the water and got about<br />> 3/4 way around the lake and the Merc made this internal rattling sound for<br />> about 10 seconds then it just died , just like it was out of fuel. It<br />> wouldnt fire at all afterwards .<br />> Got the thing home and the TOP piston is coming higher towards the spark<br />> plug hole that the other 2 . Also there is NO compression in the top<br />> cylinder. When you turn the flywheel by hand it jerks when the top piston<br />is<br />> at the top of its stroke . There is also a tiny bit of melted aluminum<br />on<br />> the spark plug . The top piston is also bright aluminum color where the<br />> bottom 2 are dark . My friend would really like to know what the cause of<br />> this was ? Dont want to rebuild it then be worried about the same thing<br />> happening again .<br />> It was flowing water good out the hole in the back , wasnt missing , the<br />> compression BEFORE was the same on all 3 cylinders . Any thoughts or ideas<br />> would be much appreciated . Thanks

 

[12Footer]

Re: 81 70hp merc

I hate when that happens

<br />If it was not too hot to touch,you can deduce the cooling system wasn't the cause,and given that the telltale was telling.But even so, some areas in the water jacket might have been blocked. It doesn't<br />take long for a "melt-down" to occur when the cooling system fails.<br />Not enough oil in the gas mix could cause this, or using the wrong oil type.<br />Should be NMMA certified, TW-C3 2cycle oil,<br />mixed at 50:1 (1 part oil to 50parts fuel).<br />Sorry to hear about that. It's going to be between 1000 and 1400 to repair. Given the age of the engine, it might not be worth rebuilding,esspecially if it has allready had a rebuild at one time or another in it's long life.<br />If it were mine, I'd look in the local paper for a same model/year motor in good condition, and change-out the entire motor.<br />I would keep the old soldier in the garage for spare parts.There is a WEALTH of parts on it still...Starter,lower unit,prop,fuel pump,carb.I could go on and on.<br />Another option is to "part-out" the old girl on E-Bay, or in the local marine trader magazines.You could quite easily get enough money to buy a good used outboard.<br />Good luck, and again, my condolances.