Merc question…..80s motor

[reivertom]

A friend of mine is looking at a mid 80s Mercury 35hp for his fishing boat. He asked me if they were good dependable motors and I really couldn’t tell him one way or the other. I’ve not heard anything about these year models, so I thought some of you guys had experience with them. Thanks, Tom

[jerry-ahrens]

I own a 1988 25 myself. Now I know you were wanting opinions on the 35 hp model, but I can give you a few thoughts on my 25 anyway. If you want speed, they will deliver. In my opinion, they are more finicky than a Johnson or Evinrude of the same period., and more difficult to work on, at least for the inexperienced anyway. They require a lot more attention to the sync and link set up, in other words the linkages, carb adjustments, timing, etc. However, when properly tuned and set up, they are a nice running engine. What impresses me most about them is the power! At full throttle they are screamers. I guess I’m an OMC man and a little biased maybe.. I bought this particular Merc 25 on a 16 ft. Jon boat [from Craig’s List] for a project, as the motor would not run. Now that I have it running again, I am enjoying blasting up and down the lake with it. I may just hang on to it a while..
One other bit of advice I can offer, is make sure you use ethanol free fuel if at all possible in these engines. This is just my personal opinion, but I know from experience that the carb on this particular motor can and will gum up if not cared for properly. In other words, don’t put it up for the season with the carburetor full of gas [with no stabilizer] and expect it to start easy next spring. I have had to go back and re clean previously rebuilt carburetors on these motors from poor or improper storage. Just something to keep in mind on any outboard.

[reivertom]

Thanks, I am a OMC guy too, but if a motor is a good one, I am not worried what the cowl has on it. My buddy wants something he can fix or get fixed if needed, and one that will get him there and back. I figured if those year models were "stinkers" I would have heard something by now. I just don’t know anybody that has smaller hp Mercs around here. Thanks.

[billw]

I think the mid-eighties Merc 35s were just GREAT motors. Just about as bullet proof an engine as Mercury ever made, in my opinion. I used to service a LOT of them, we had one on our work boat for years and I even owned on myself, on a Boston Whaler. Performance on a 13 ft Whaler was close to their fifty hp, while using about half the gas, if it has a thermostat installed. (Some did, some didn’t; but one can be easily added.) And this was all on salt water, too. I can’t even imagine how good they would be on fresh. DO put an impeller in them every two years, though; and if the condition of it is unknown, just put one right in, no question. Compression should be 120 and up. Spark should jump 3/8" and up. You might want to check that the lower unit WILL come off. They had a funky drive shaft-to-crank shaft seal that would let go. (Always replace with the impeller) SOMETIMES, we’d get one with the driveshaft stuck in the power head; but that was fairly rare.

Long live American manufacturing!

[reivertom]

Thanks for the replies. This is definitely NOT an area that I know anything about and I will take it all in and digest it a while.

[chinewalker]

I’ve got three of the 35hp twins in my shop right now, all purchased from local marinas, all falling into the 1985-1986 range. One was a running take-off. 135 psi in both holes, it’ll get basic tune-up stuff. Second had eaten one of the rod bearings at the crankshaft. Suspect it was due to moisture (poorly winterized? water in gas?) issue resulting in stuck bearings, then run, then melted bearing, then, well, enough knocking where they finally figured something was wrong and stopped running it. It’ll get rebuilt, as the bores are okay and I have another crank, bearings & rod for it. Third looks like it overheated and scored a piston, enough to stick a ring. Nothing broke, so it, too, will eventually live again. None have broken cranks, and the two that died had owner-neglect issues, not design issues. Over the years, I’ve had several of these big bore twins, from about 1979 & up. They seems to have ironed out most of the bugs by that point. I also have a much earlier 1969 35hp and 1966 35, and both are solid runners.

[reivertom]

It looks like it might be a good choice….even for an OMC guy!

[billw]

My old boss, that owned the work boat , was a die-hard OMC guy from the sixties. He still has his 1966 Johnson diploma hanging on the wall. That 35 Merc (an ’83) convinced him Mercury had come a long, LONG way. He liked it a lot.

Long live American manufacturing!

[jeff-register]

These twins were built for in house testing on the assembly line. They functioned so well they were introduced to the general public in the outboard form. Mercury is very sensitive to being stored correctly & all outboards require service. Be sure to refill & the gearcase with fresh lube as well. Keep the fuel clean & mixture correct using quality oil.

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