18' G3 F60 Yamaha Low RPM's

[hbulle13]

Hello,

I have a new 2009 18' G3 Pontoon boat with a F60 Yamaha 4 stroke.
Usual load = 3-4 people, 20Gal gas, 100lb's gear

From the dealer it came with a 10 5/8 x 12 Prop (3 blade alum.).
On dead calm water, it ran about 19MPH(spd gauge) at 4200 RPM WOT

The dealer checked and my throttle is correctly set.

I replaced the prop with a Turning Point Hustler 12 1/2 x 8 (3 blade alum.) and my numbers came out to 20MPH at 5000 RPM's WOT ( in reverse it is VERRY slow now. my trolling motor is faster.)

The dealer said that the motor is supposed to run between 5-6000 RPM, and the ideal point in my setup is about 5700 RPM.

Of course I would like to have as fast speed as possible , but my main concern is getting it to the correct RPM's before I get too many hours on the engine.


Any suggestions as what prop to try next, or anything else I may have missed.

 

[EGlideRider]

Re: 18' G3 F60 Yamaha Low RPM's

I wouldn't change the prop again until the motor is well broken in, maybe 30 or 40 hours.

An 8" pitch sounds awful low to me. If the RPM's don't come up after the break in period, I would be back at the dealer. It is their responsibilty to deliver to you a properly rigged boat.

 

[DMAN1968]

Re: 18' G3 F60 Yamaha Low RPM's

Have the dealer check the tach settings...I think you might find the problem there. An 8 pitch prop should have seen a much larger increase than just 200 rpm.

 

[hbulle13]

Re: 18' G3 F60 Yamaha Low RPM's

It was an increase of 800 RPM's. I think part of the problem with the new prop, is I didnt have it tight enough. When I took it off, I could almost unscrew it with my fingers. I've tightened it and will try it again later today.

Thank you very much for your responses.

 

[DMAN1968]

Re: 18' G3 F60 Yamaha Low RPM's

Sorry for the misread. Still, I would have the tach checked as a pitch that low on a 60 should be well over the max rpms. It could be as easy as turning the tach setting to coincide with your engine.

 

[EGlideRider]

Re: 18' G3 F60 Yamaha Low RPM's

I agree with DMan that you should confirm the accuracy of your tach. Your dealer can connect a computer to your motor and tell you the max RPM's that your motor has turned. He can also tell you the length of time that it has been run at other RPM's.

 

[Silvertip]

Re: 18' G3 F60 Yamaha Low RPM's

Something is very wrong with your numbers, the tach, the prop, or the engine. I have an 18 foot Misty Harbor with 40 HP Suzy 4-stroke. It spins an 11x11 three blade prop and tachs 5500 with five adults and an 8-year old. An F60 on that boat should have no trouble spinning an 11 or 12P prop IF it is a high thrust motor (2.33:1 gears). If it's a standard F60 (1.85:1 gears) that is no motor for a pontoon. Check the post about the guy that's at the end of his rope trying to make a non-big foot Merc 50 work on a pontoon. Same issue. You need a big prop and different gears on workboats, barges, and pontoons.

 

[lakegeorge]

Re: 18' G3 F60 Yamaha Low RPM's

I have the F-60 Yamaha also and it swings a 14 x 11 alum. prop at 5600 rpm on a 21 Sweetwater at 21mph by gps.
You should get more rpm's and run in the low to mid twenties with the right prop.
I would try the 14 x 11 I'm very satisified with my results.

 

[rickdb1boat]

Re: 18' G3 F60 Yamaha Low RPM's

Sounds like a standard gearcase if the prop you're running now is only 10 5/8" diameter..

 

[hbulle13]

Re: 18' G3 F60 Yamaha Low RPM's

My engine is an F60 with the 1.85 gear ratio. I dont know that a 14" prop would fit.
How do I go about telling the dealer that the motor shouldn't be on that boat... If that is the problem?
Thank you all for your time, I will contact the dealer with all your posts and suggestions and get back to you.


Brian

 

[Silvertip]

Re: 18' G3 F60 Yamaha Low RPM's

Yamaha and Mercury both have low ratio (high gearing) on their standard engines. The idea is that high prop speed combined with a small diameter prop produces the desired result on a planing hull. That is exactly why they also offer a High Thrust (Yamaha) and Big Foot (Mercury) lower unit. Work boats and barges are non-planing hulls and therefore need a lot more push. Just like your tow vehicle, it needs deeper (higher rear axle gear ratio) for towing than for economical cruising. So the Yamaha High Thrust and Mercury Big Foot engines have 2.33:1 gears in a larger lower unit that allows installation of props up to 14 inches in diameter. Outboard on pontoons operate in very turbulent water so the prop needs to big and needs to sit lower in the water. Standard Yamaha and Merc engines should therefore not be selected for this duty. Chances are you will not get any sympathy from the dealer since he/she is likely to say "we do that on all our boats". Well -- that doesn't say much for the integrity of the dealer.

 

[CBR75]

Re: 18' G3 F60 Yamaha Low RPM's

I just purchased a 2009 Suncatcher 188C with the Yamaha F75. We had it out for the second time this weekend and it ran 23-24mph (spedo) at 5700 RPM WOT, 3 blade aluminum 13" diameter prop. I don't know enough about different prop pitch and sizes to speak intelligently on the RPM situation, but I think you are right where you are goinig to be as far as MPH with this set up. While the High Thrust Yamaha may very well be a better motor for a pontoon the 2008 and 2009 G3 catalogs do not even list them as engine options for the Suncatchers so I don't think you have the wrong motor for the boat so to speak. Yamaha's web site has a performance bulliten on an 18foot Quest pontoon with the T60TLR (high thrust) and it topped out at 20.1 MPH @ 5700 RPM. I agree with DMAN and would start with having the tach checked out. Have you had it back out since you tightened up the prop?