Hey, I was just reminded… Recently I added the high thrust propeller to my 5hp Tohatsu/Nissan 4 stroke.
I got one of those digital tachometers which work on inductance around the spark plug wire. Very cool.
First of all, there's no way I could run my idle speed at 1100rpm like the Seloc manual states. I'm running around 750rpm, and so far it's fast enough it doesn't conk out on me.
I used to hit 2150rpm at WOT with the factory prop. The only marking on that prop was an 8 in a square, stamped on one of the blade roots.
With the 3 bladed elephant ear high thrust prop, I'm now able to hit 2340rpm at WOT, for 6.2 knots - well over my theoretical hull speed.
At idle, in gear, under load, I have that 750rpm, at about 1.4 knots.
Coming into the slip, when I throw it in reverse, the boat will actually slow down and stop now. So, that's a nice bonus.
Boy, that 8 1/4" diameter is reeeeeel close to the anti-ventilation plate, but it fits with maybe 1/4" clearance. At idle speed, probably because of the close tolerances, there's a weird new harmonic vibration you can feel in the boat, a whumpwhumpwhump.
So far, I motored maybe 4 miles for 2 no-wind motor cruises this past weekend, under 1/2 throttle (didn't measure rpm for actual 1/2 speed, oh well) at about 4.2 knots. No problems to report, so I guess that resonance isn't causing problems YET.
If you have an outboard on your displacement sailboat, and you still have the factory prop, I bet you'd see a big improvement if you swap into a high thrust prop. Mine was only $90 with shipping. Not a bad upgrade.
I got one of those digital tachometers which work on inductance around the spark plug wire. Very cool.
First of all, there's no way I could run my idle speed at 1100rpm like the Seloc manual states. I'm running around 750rpm, and so far it's fast enough it doesn't conk out on me.
I used to hit 2150rpm at WOT with the factory prop. The only marking on that prop was an 8 in a square, stamped on one of the blade roots.
With the 3 bladed elephant ear high thrust prop, I'm now able to hit 2340rpm at WOT, for 6.2 knots - well over my theoretical hull speed.
At idle, in gear, under load, I have that 750rpm, at about 1.4 knots.
Coming into the slip, when I throw it in reverse, the boat will actually slow down and stop now. So, that's a nice bonus.
Boy, that 8 1/4" diameter is reeeeeel close to the anti-ventilation plate, but it fits with maybe 1/4" clearance. At idle speed, probably because of the close tolerances, there's a weird new harmonic vibration you can feel in the boat, a whumpwhumpwhump.
So far, I motored maybe 4 miles for 2 no-wind motor cruises this past weekend, under 1/2 throttle (didn't measure rpm for actual 1/2 speed, oh well) at about 4.2 knots. No problems to report, so I guess that resonance isn't causing problems YET.
If you have an outboard on your displacement sailboat, and you still have the factory prop, I bet you'd see a big improvement if you swap into a high thrust prop. Mine was only $90 with shipping. Not a bad upgrade.
