Johnson vs Merc

[cesandroid]

Hey everyone gotta choice between a 78 merc 85hp or a 86 johnson 90hp. Both I’m told in good shape, the 90 was rebuilt before current owner who has paper work. Both around the same price. Any thoughts on choice? Thanks

 

[jimmbo]

Both are fine engines if maintained. However there are major Differences between them. Mainly Displacement. The Johnson has 50% more Displacement(99.6 vs 66.6 for the Merc) which means a lot more Torque. The Johnson is also Prop Rated, and the Merc is Crank Rated. Top Speed should be within 3 mph. The Merc will be a little better regarding Fuel Economy, because of the smaller Displacement. Do both have Power Trim? Here the Johnson has a better design.
Merc has a 2.3:1 Gear Ratio, the Johnson 2:1
Both are old... Mercs often have problems with the Wiring on the Engine. Mercury used a Wire with an Insulation that crumbles as it gets old. They must have bought enough of the stuff to go to the Moon and Back, as for Decades, Mercs have had this issue, and need rewiring, or new Harnesses.

 

[cesandroid]

Hmm okay thanks. Yes both have trim and tilt.

 

[jimmbo]

Only you can decide which to buy. I have owned both Mercs and Johnson-Evinrudes, and I can say they a both Good, or both Junk. The Mercs tend to be a little more Finicky when it comes to tuning, but that is because of more Hp per cubic inch Displacement. If you plan to use the Boat for Skiing, Tubing, the higher Torque Johnson has an Advantage

 

[Faztbullet]

Depends on what you are going to use it for and type hull

 

[cesandroid]

15 foot tri-hull mostly fishing cruising.

 

[airshot]

Sounds like a lot of hp for a 15' tri hull ??? Tri hulls haven't been made for many years so the odds of having a hull with internal rot on stringers and transom is quite high, unless you are currently rebuilding this hull. Not tryin to burst your bubble here, just want you to be prepared....

 

[jimmbo]

Not a tri hull, 15 ft, rated for 90hp. Purchased from dealer as is in 82

 

[cesandroid]

This boat is rated for 100hp. 70 does okay but is getting tired.

 

[JimS123]

My experience with Mercs in that time frame wasn't good. Today, their 4-strokes are bulletproof.

A JohnnyRude in that time frame would have been my choice. But, you said "rebuilt". That would be a deal breaker for me. Obviously, a PO didn't maintain it well.

Personally, I'd keep looking. But that's just MY opinion.

 

[jimmbo]

But, you said "rebuilt". That would be a deal breaker for me. Obviously, a PO didn't maintain it well.

Pretty much every OMC Crossflow V4 will break a Piston Ring. There is an Unwritten Law that says they Must, regardless of how it was or wasn't Maintained