1-cyl vs 2-cyl

[Thomas Gilg]

My quest for a drift boat motor continues. In my prior query "4hp vs 8hp", you all convinced me I should be looking more towards 8hp than 4hp.

Looking at some stats (HP - lbs - cyls-displacement):

4/6/8 HP Yamaha - 48/83/83 lbs - 1-112cc/2-197cc/2-197cc - 15"
4/6/8 HP Mercury - 55/55/84 lbs - 1-123cc/1-123cc/2-209cc - 15"
4/6/8 HP Nissan - 57/55/82 lbs - 1-123cc/1-123cc/2-209cc - 15"
4/6/8 HP Nissan - 60/57/84 lbs - 1-123cc/1-123cc/2-209cc - 20"
2/5/8 HP Honda - 27/60/92 lbs - 1-057cc/1x127cc/2x222cc - 20"

(Mercury and Nissan use Tohatsu power-heads)

I'm really atracted to the the 50-lb class 6hp motors vs. the 80-lb class 8hp motors, and at this point I'm really looking hard at the 6hp Mercury. However...

All of the 8hp's are 2-cylinder, while many of the 6hp's drop to 1-cylinder, including the Mercury. Are there any smoothness or quietness or power or reliability differences between 1-cyl and 2-cyl?

Also, a single displacement (123cc Merc) supports multipe hp's (4/6 Merc) per different tunings. A co-worker tells me the lower hp motor for a given displacement will have a nice even torque curve across various rpms, where-as the higher hp motor at the same displacement will have a torque ramp from low to high rpm. Again, are there any meaningful differences here? For trolling, is it better to have a motor that can generate good torque at low rpm than not?

The 6hp Mercury at ~57lbs sounds adequate power and weight wise. I'm looking for last minute things that would cause me to reconsider.

Thomas Gilg

[treegolfer]

I have a 4HP Yamaha 4 stroke single that is a great trolling and low RPM motor, very quiet and smooth. That being said, the higher the RPM the worse it vibrates. It rattles everything in the boat including passengers. I really wouldn't want to try to run up a river or across a lake in any kind of a hurry. If I was going to use a motor for anything other than trolling or emergency use, it would be a twin cylinder.

treegolfer

[StickFish]

The one lungers do vibrate - buddy has one and it shakes his 16 Osprey pretty good

[FastActionRodTip]

my 2005 8hp Johnson 2 cylinder 2 stroke weighs 61 lbs...very nice bulletproof motor

[FastActionRodTip]

definately stay away from the single cylinder models...basically a paint shaker with a prop...2 cylinders provide counterbalance/smoothness and makes for a less tiresome day on the water

[ArtB]

I bought a used boat last year with 40 & 5 hp Nissans, the latter single cylinder four stroke. I was a bit dismayed by the vibration on the 5 at first but I have gotten used to it and it trolls all day on about a pint of gas. It is on a drop-down mount which may absorb some vibration. I would say that if you want a good kicker at a very reasonable price, go for it.

[ondarvr]

If cost is not a factor and you can lift it, go with the 8hp, you will like it better in the long run. If you can't or have big problems lifting the 8, then the smaller motor will work. Most of the 8s have larger lower units and props, that means more thrust and better control. I've used all sizes on my DB and bigger is better in this HP range.
In the past most of the single cylinder motors were desingend to be light, cheap and for limited use. One reason for the jump in weight when going to an 8hp, is that it is built to be used harder and for a longer period of time.

[ET]

Maybe in your case the 2-stroke is the way to go.

I ran a 2-stroke, 2-cylinder, 6hp Johnson for years. It was bulletproof and light. A friend has a new 2-stroke and it is very quiet and smokefree. Less expensive too...

I now love my 8hp, 4-stroke, 2-cylinder Yamaha, but the 83lb dry weight would deter me from calling it "portable".

The first company to make a 4-stroke, 2-cylinder, 8hp motor that weighs 50lbs is going to dominate the market.