1986 Mercury 75 hp 4 cyl vs 1991 Mercury 75 hp 3 cyl.

[mgsolakis]

1986 Mercury 75 hp 4 cyl vs 1991 Mercury 75 hp 3 cyl. Which one is better? I assume the newer 3 cyl would be better on gas. Would the 4 cyl idle better? Do either of them troll well? The 3 cyl is oil injected is that a good thing? Which is faster? Which one is better? I assume the newer 3 cyl would be better on gas. Would the 4 cyl idle better? Do either of them troll well? The 3 cyl is oil injected is that a good thing? Which is faster?

 

[oldman570]

Re: 1986 Mercury 75 hp 4 cyl vs 1991 Mercury 75 hp 3 cyl.

Both motors are good for their use. Better idling on the 4 cylinder and both should idle about the same RPM. Fuel usage should be near the same. Oil injection is up to the mind of the owner. Both should use near the same prop and the WOT and speed near the same. Each motor has its faults, and parts can be found for both. Guess you have to make up your own mind on which is best for you. Use of a coin flip is just as good. JMO
Oldman570

 

[mgsolakis]

Re: 1986 Mercury 75 hp 4 cyl vs 1991 Mercury 75 hp 3 cyl.

Thanks Old man. I was hoping one might troll slower. But perhaps all of the old motors just troll fast.

 

[Texasmark]

Re: 1986 Mercury 75 hp 4 cyl vs 1991 Mercury 75 hp 3 cyl.

I had a 4 cyl. 85 of the early-mid '80's. It may have been "direct charged". I just don't remember. It was as fine an engine as I ever ran. Whether it is the old cross flow design, cross flow with direct charging, or loop charged makes a significant difference in fuel consumption. I currently have a 90 triple, loop charged, that is the big brother to the '91 triple 75. It is a fuel miser, course as I recall the 85 wasn't all that bad.

I would say that since the engines are only 4 years apart, the corrosion and all considerations are really more about what kind of care did each engine receive in it's lifetime. Idle rpm for the 3 cyl is 675 +/-. Don't remember on the 85, course your engine to prop gear ratio and prop pitch will come into play too. They do make after market deflectors which are a flat plate that drops down behind the prop to slow the boat while trolling.

If you are going to do a lot of trolling then I would suggest the triple. Oil injection systems have a lean 80:1 fuel to oil ratio at idle which will help in reducing plug fouling under trolling conditions. At WOT it moves up to 50:1 as the 4 cyl used with premix.

HTH,
Mark

 

[mgsolakis]

Re: 1986 Mercury 75 hp 4 cyl vs 1991 Mercury 75 hp 3 cyl.

Right now I'm using an Evinrude 75 hp Hustler and it's a great motor but it trolls way too fast. I actually tried that trolling plate but it slows the boat down to a crawl/almost no movement at all. I thought about cutting the plate down but then I figured maybe the 75 merc would be good. I know it would be faster because it would be rated at the prop.

 

[Texasmark]

Re: 1986 Mercury 75 hp 4 cyl vs 1991 Mercury 75 hp 3 cyl.

One thing for sure, the Hustler is loop charged and you would be hard pressed to beat it's fuel economy unless you had another looper.

Mark

 

[mgsolakis]

Re: 1986 Mercury 75 hp 4 cyl vs 1991 Mercury 75 hp 3 cyl.

Yes I think I am leaning to the loop charged 3 cyl Mercury 75 hp if I decide too change. I really like the Hustler it's just to bad it trolls so fast.