Re: Mercury 70 hp (3 cylinder)Advice Urgent
That should be a pretty good engine, the 70 was the less-stressed version of the 3-cyl's, and Merc pretty much had the initial design problems with these motors all fixed by the mid-90's. <br /><br />Providing the compression readings are all within 5 psi of each other I wouldn't worry. A leakdown test would be more accurate if the dealer is capable of doing one.<br /><br />By all means test run this motor in the water. It should start well, shift smoothly, not be fussy at idle and shouldn't die when shifted to gear.<br /><br />It should pull its rated rpm at wide open throttle.<br /><br />And shouldn't make any nasty, thrashy noises. <br /><br />A buddy of mine rebuilt a 1991 90 hp Three and I was impressed by its low end torque. Had plenty of snap for slalom skiing and was very economical.<br /><br />It was pretty quiet too, compared to my old Merc 1000!!!<br /><br />The Three's of course don't idle as smoothly as a 6 cyl but there's a diff between the normal shaking of an idling 3-cyl and one that's running badly so be aware of that distinction. <br /><br />If you don't like the idling qualities of a 3, look for a 4-cyl motor such as a JohnRude V4 which are very smooth at idle. <br /><br />But, can't recommend any of the later Merc 4-cyl's due to the 2-4 idling setup, they are problematic and have a strange surge at 1800 rpm when all the carbs kick in. The Threes don't have that, though.<br /><br />HTH & Good Luck........ed
