help me decide

[fins&gills]

buying new (used Motor) same price for both one is a 89 75 hp and the other a 85 80 hp both mercs both look good is there any thing that would make me buy one over the other the hp diff dosen't matter to me. someone told me the fuel econemy on one of these is not good, any insight would be helpful thank you

 

[emckelvy]

Re: help me decide

You should have compression checks taken on both, and if they are not virtually 'perfect' I wouldn't buy either.<br /><br />The '89 should be a 3-cyl model which would be somewhat more economical than the 4-cyl 80 hp. The 3's have some internal issues so if there's anything that doesn't seem right about the way it runs, I'd stay away from it. But they are a torquey motor, my skiing buddy had a 90 which had no problem pulling a slalom skier, and the 75 has the same displacement, just tuned differently. It should be somewhat quieter than the 80 due to the clamshell design of the engine cover. The 75 should also be oil injected if I'm not mistaken.<br /><br />The 80 is an older design and wouldn't be as fuel efficient, but if it's in very good condition it wouldn't be a bad choice, either. The 75 does have a better-designed lower unit with improved water pump. I replaced and impeller on one that had run 7 years and it was like new.<br /><br />Another thing of note: the 75 has a thermostat and will likely idle better in very cold water; the 80 has none.<br /><br />You might run both of them, and see if you prefer the idling & at-speed characteristics of one over the other; the 3 definitely runs differently from the 4.<br /><br />Anyway, that's just a few random thoughts, maybe some of the other fellers will have more to add.<br /><br />HTH and Good Luck........ed

 

[fins&gills]

Re: help me decide

internal issues???, also is one alot heavier than the other. compression is near perfect on both both look very clean and well taken care of. My thinking is five years newer five years better, all things equal cause they dont have odometers.

 

[KCLOST]

Re: help me decide

Weight shouldn't be much different from one to the other... Might check the specs to confirm...<br /><br />I'd pick the best "conditioned" motor... CHecking all the important variables...

 

[JB]

Re: help me decide

General Outboard (non-repair topics)

 

[emckelvy]

Re: help me decide

Late 80's/Early 90's "new-design" 3's and 4's have bottom-guided rods, i.e. the rod big end thrusts upon the sides of the crankshafts. In this motor, it caused problems with excessive wear on the crank and failure of the rod bearings. My buddy bought a 90 which had blown up because of this. Replaced the crank, rod, piston, welded up the case, and it ran like a champ!<br /><br />Merc changed the design of the motors in the mid-90's to a top-guided rod, whereas the thrust of the rod is taken up at the wrist-pin end, and the big end of the rod just 'floats' on the crankshaft. Apparently more durable and produces less friction for more power, too.<br /><br />That notwithstanding, probably takes many many hours for this design flaw to arise, if ever. <br /><br />You've definitely got to hear both motors run and if the 75 sounds great, it'll probably be a better motor all around than the 80. Just be sure to use non-alcohol fuel and a premium, synthetic oil. Wally's sells Penzoil full synthetic for a great price and have seen good reviews on the oil.<br /><br />HTH.......ed