Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: 1987 15 Sport w/F60 Yamaha mounting height

Posted by Dave1966 on 07/28/15 - 1:07 PM
#1

Could anyone who has such a set up share ideal mounting height as well as what prop they're running. I just repowered with a used (2010) F60...dealer has mounted all the way down which I think is too low.

Thanks

Posted by wlagarde on 07/28/15 - 1:32 PM
#2

2 or 3 holes up. Start with 3 holes up and if it aerates while rising onto the plane move it to 2 holes up.

Posted by wlagarde on 07/28/15 - 1:34 PM
#3

Also can you tell us your current WOT rpm and what prop you currently have.

Posted by Dave1966 on 07/28/15 - 2:04 PM
#4

I'm ashamed to say I don't know the prop size and the makings on the outside don't seem to indicate what it is. I guess I need to remove it to see if there are markings on the inside of the hub. As for current WOT...6,100+ish. If I raise the motor to the proper height, is my understanding correct that will need to increase pitch.? Perhaps I should anyway? I don't run the motor anywhere near WOT but would like to get the best/most efficient performance.

Posted by wlagarde on 07/28/15 - 3:04 PM
#5

The goal is for your WOT rpm to be at or near the upper limit of the operating range of the engine (6000 rpm; http://www.yamaha-motor.com/assets/se...2_1808.pdf) when you are running your lightest load. Since you are currently over-reving at WOT then you will need to pitch up. For every hole you raise the engine the WOT rpm should increase by ~ 200rpm or so. For every 1 degree you increase the pitch (for the same brand/model prop) the rpm will decrease by ~250rpm. Be sure to confirm the 6000rpm number via your engine owners manual.

The markings/numbers you are seeing on the prop might be a part number. Can you post it? Also, is the prop an OEM Yamaha prop?

Tom and others will be able to give you the best help with choosing a prop for your setup.

Edited by wlagarde on 07/28/15 - 4:00 PM

Posted by dgoodhue on 07/29/15 - 10:10 AM
#6

The mounting height depends on the prop. A yamaha SS or Stilletto prop will like 3 holes. Most aluminum props will happier with 2 holes up.

Posted by Dave1966 on 08/03/15 - 5:58 AM
#7

I'll get the makings I can see on the prop and post. The current prop is aluminum which I intend to stay with.

Posted by Dave1966 on 04/13/17 - 6:36 AM
#8

Sorry for the delay in posting prop detail... I intend to raise the motor to at least one up, possibly two. The prop currently on the motor is 10 5/8 x 12. I realize achieving max efficiency is a challenge but am wondering if this prop even gets me in the ballpark. I don't generally run the boat with a full load, usually two adults and 6 gallons of fuel. As currently set up (motor all the way down) the boat gets out of the hole well but I question efficiency at cruising speed. Any input is appreciated.

Posted by Phil T on 04/13/17 - 1:16 PM
#9

You need to raise the motor to 2 holes, then test for WOT rpm's. All the way down is just wrong.

It is not about going WOT, it is about tuning the setup for optimum performance at slow, medium and high speed.

If mounted 2 holes up with that load, you would want to reach 5500-5600 rpm's at WOT. 6K if all by yourself.

Posted by tedious on 04/14/17 - 4:57 AM
#10

Dave, I think you set a new record for the longest meaningful thread time gap!

Your motor is mounted way too low. Your lower unit is dragging in the water at all speeds, causing a loss of efficiency and potentially hard steering. You may also be noticing some porpoising when trimmed out for speed, and excessive splashing - those are also symptoms of being way too low.

First raise the motor two holes - you may be able to go up one more hole (to all the way up) but two holes up will work with almost any prop. Then go give it a test run, loaded fairly light. Based on your previous reports of performance, it is likely you are going to find you're able to go above the maximum recommended RPM (6000). Your motor has a rev limiter, so you won't hurt it, but I still wouldn't run it more than about 6100).

So now you will very likely need a new prop. You state that you want to stay with aluminum, yet you are interested in efficiency. Stainless steel props are certainly more efficient and perform better in general. Some people want to stay with aluminum because they have heard the old wives' tale that an aluminum prop will save your motor's gearcase in the even of a rock strike. That's simply not true - all props today, both stainless and aluminum, are made with breakaway hubs that work to prevent damage. If you hit a rock, you may or may not damage your gearcase with either type of prop.

So my recommendation would be to go with a good quality, stainless steel prop. You will likely want to go up in pitch, but be aware that pitch is only one factor - blade size and shape matter as well. In general, for 4-strokes such as yours, a prop with less blade area lets them spin up more easily into the range where they make their power. You'd certainly want to stay with 3 blades, not 4, for the same reason.

You may need to experiment a little to find the correct pitch, so if you can find a way to try before you buy, that would be perfect. Some prop manufacturers such as PowerTech offer both advice on prop selection, and a trade-in program to let you swap for a different pitch if needed. I went with PowerTech, purchased online from Dan's Discount Props, and was very pleased with the results.

Good luck with it!

Tim

Edited by tedious on 04/14/17 - 6:01 AM

Posted by Dave1966 on 04/18/17 - 12:22 PM
#11

Thanks for the input. I'll certainly start by raising the motor and go from there. As for a prop, I had intended to stay with aluminum for the reason you mention, perhaps I should reconsider. Thanks again for the help.