RPM on 115 yamaha 4 stroke

[Northlander]

How many RPM's should I be running top speed of 47 mph with my yamaha 115 4 stroke on a 17' Lund Explorer 2004 model? Im at 5500-5700 but someone said I should be running more RPM.
What should I expect to troll down too? Less than 2mph? On Gps ofcourse.
What are people finding out is their best pitch on a Stainless 3 blade prop and what type?

[Northlander]

Thanks guys. What are you all getting them to trol down to and what props are working best? Im getting 2.0-2.2 mph troled down with a 17 pitch stainless.

[This message has been edited by Northlander (edited 07-05-2004).]

[ChuckN]

Hey Northlander,
My dad has this motor on a Trophy 175 and it runs higher RPM's, like 5900. He only has the stock prop and I really don't know the size. Trolling is around 3 mph, too fast IMO.

That's a high rate of speed for that boat/motor combo!

[Diezel350]

Rpm range for the motor is 5000-6000 run it closer to 6000.

[wastewaterguru]

I have a 17 pitch on my 1700 Fisherman and get 43 or so gauge mph at 5900-6000 rpm with two guys/gear/and gas.

The main thing I like about the stainless is the quick hole shot. That is the reason I stayed with the 17 instead of the 18 or 19. If you use your boat at all for pulling tubers or skiers, I would say go with a 17 or even down to a 15 if your trying to get up an adult on skis.

Also, from a theoretical standpoint, a smaller pitch prop will troll down slower at idle rpm. I don't troll with mine cause I just don't think it's a good idea to run a motor that size at low rpm's all the time. Kinda like being stuck in traffic with your car.....it puts a lot more wear and tear on the motor.

With the lower pitch, you just have to be careful not to go over rpm's. When I had the 15 on mine last year and when I was light loaded, I had to stay at 80 or 85% throttle (36-38 mph)or trimmed down to keep rpms in check. But man did it get up and go.

The prop I have is a Turbo (brand name) and I got it from a shop off 694 on the upper west side of the cities. I can't remember the name of the shop off hand, but they had a return policy that allowed props to be returned (as long as undamaged) up to 60 days or something. So I bought a 19 and couldn't get rpm's high enough....traded it for a 15 and had a little too many rpms.....and then traded for the 17 and have been very happy with it.

[This message has been edited by wastewaterguru (edited 07-02-2004).]

[Northlander]

Thanks guys. Im running a 17 as well and get about 44 mph with 2 guys, gear and full tank. Turning between 5500 and 5700 rpm. Does that sound good to you guys?

[Surface Tension]

Steve I'd be dancing in the street with those specs.

[Double Barrel]

I've got one on a 1700 Angler.I get 5700 rpm's and 43 mph with an 18 pitch. I had a 20 pitch on it and got 44mph , but only 5200 rpm's.

[upnorth]

As long as your within the recommended top operating range of RPM you should be fine. Towards the upper end like you are is better, it puts less load on the motor while trying to get on plane and such. I wouldn't change a thing.

The best thing about a stainless steel prop is that it won't flex and distort on top end losing pitch like aluminum, gets you a couple of mph on the top end.

[Northlander]

Ok then I guess Ill keep things as is.