mid 70's merc 65 hp any good?

[mnhunter2]

Just got a 65hp merc for free from a buddy that thinks it has a scoured piston and i know nothing about this motor/model and was wondering if it would be worth repairing?

 

[Chinewalker]

Re: mid 70's merc 65 hp any good?

I think you'd be hard pressed to find a Mercury mechanic who would praise those first years of the Merc triples in the early/mid 1970s. They scored a lot of pistons... They had the habit of forming steam pockets in the water jackets, which resulted in hot spots in the cylinders. There are fixes for this, so you might want to seek out a long-established Merc guy in your area to show you the ropes...<br /><br />On the upside, when they worked, they put out good power for their size. They must be propped to the high end of their RPM range in order to last. They are not good barge/houseboat motors because of their gearing, but they did make decent ski motors on lightweight runabouts.<br /><br />- Scott

 

[emckelvy]

Re: mid 70's merc 65 hp any good?

Your best bet with a 3-cyl (unless it's very very clean and shows absolutely no sign of overheating) is to part it out on eBay!<br /><br />Watch out for cracked cyl blocks because of the above described overheating issues.<br /><br />I you feel like practicing, you might be able to get away with a 'quick and dirty', minimal rebuild but I wouldn't throw a ton of money after it. A used piston from any power-ported Inline Six or Big Four will fit this motor.<br /><br />Also check the lower unit for signs of water in the oil. This may help you make a decision about whether or not it's worth fixing. The early 650-3's did not have a stainless driveshaft, so were prone to rusting-out at the seal area under the water pump body. This is fixable but not necessarily cheap. Either with Speedi-Sleeves (cheapest), or lower unit disassembly for shaft repair or replacement.<br /><br />The older, 4-cyl 650 was a much better motor. The 3 was just cheaper for Merc to mfr. so they phased out the better motor.<br /><br />HTH/G'luck...........ed