For what it's worth, on my 17 I run a 2hp Honda. It's just sips the gas at half throttle...a pint will last close to 2 hours depending, maybe more. It will do about 3.5 kts at about 1/3 to 1/2 throttle in still. I sometimes wish I had a little more power, but mostly it's fine. Full throttle will get you close to hull speed in still and lots of noise. I'd like 4 or 5 knots without the noise of full throttle. Is the 3.5 the ticket for this? Jazz On Aug 14, 2017 9:17 AM, "Steve Trapp" <stevetrapp@q.com> wrote:
David, You must be a senior citizen like me to remember the 25hp and 40hp motors used to water ski when we were in highschool. I always thought we ran those motors hard because we needed every bit of power to pull a water skier, and really did not notice much difference when I upgraded my dad's boat to 65hp except needing to buy more gas. Nowadays I am content with the 4hp on my M-15. Steve M-15 # 335
-----Original Message----- From: David Rifkind Sent: Sunday, August 13, 2017 2:10 PM To: For and about Montgomery Sailboats Subject: Re: M_Boats: 3.5 tohatsu for m17
On Aug 12, 2017, 12:44 AM -0700, jerry@jerrymontgomery.org, wrote:
I don't claim to know what I'm talking about, but I suspect that the motor doesn't really care how fast it's being run. I grew up with outboards and I remember carbon problems with motors that were not run fairly hard. 25s and 40s were as big as they got when I was in hi school, and when used for water skiing they would last all summer w/o changing the plugs, but if we did much fishing, new plugs every few days.
Very normal for two-strokes. All the factors--timing, carburation, cylinder stuffing--only line up at one speed, and they're usually designed so that speed is WFO (wide open).
I think it's interesting that on this Johnson 4 the speed lever is attached to the timing plate, not the throttle. Through most of its range the engine is running at what ought to be idle, with the timing retarded to reduce power. It's only at the very top end that the throttle plate starts to open.
That's how it kept fooling me. The engine started to sag because the mixture was wrong. I'd blip the throttle to keep it running, but because that doesn't actually open the throttle it died anyway.