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View Full Version : Yamaha F115 Jet / SS Impeller Update!!

reelfine
05-14-2005, 12:32 PM
When I first got my boat (18' North River Scout) w/ the Yamaha F115 4-stroke jet, I was a little disappointed in the performance; primarily the time to plane (on-step) and its ability (or lack thereof) to stay on plane at lower speeds.
:shrug:

I asked around about performance upgrades for the motor, and some people suggested a stainless steel impeller. When I asked some service shops about it, the answer I generally got was "that motor is too small to run a stainless steel impeller and get any benefit out of it". It wasn't a matter of ignorance, just that the motor is semi-new and no one seemed to have a lot of experience with trying out upgrades on it. However, someone finally directed me to Glenn Wooldridge at Wooldridge Boats since he seemed to be the expert on stainless steel impellers. After talking to Vince at Wooldrige, he indicated that he thought that there would be plenty of benefit derived from installing a SS impeller, but still cautioned me (and rightfully so) to not expect any "miracle" cures, since the SS impellers still were primarily designed for larger, V6 motors.

Well, unhappy with the existing performance, and knowing that it would drive me to trade-in/sell before too long, which I did not want to do, I decided to just take a $400 risk and have it done.

This morning, I took it in and had Wooldridge install a SS impeller in my motor and then headed out to Lake Washington for a comparison test.

It was a #$((*&!(* MIRACLE! :dance: :yay:

Here are the before and after stats that I took. Note that the times were taken using a wristwatch, so its not scientifically precise, but definitely indicative of the change. On-step here means "the time it took from boat at idle to on plane":

Before:
On-Step: ~6 seconds
RPM's required to stay on plane: 5100
Top Speed (WOT/GPS): ~32

After:
On-Step: ~2 seconds (or less)
RPM's required to stay on plane: 3900
Top Speed (WOT/GPS): ~36

I know that I have previously been pessimistic in other threads about installing a SS impeller on a 115, but I HEARTILY advocate its use now.

I will NEVER own another aluminum impeller, unless it is for spare parts purposes.
reelfine
05-14-2005, 12:33 PM
btw, Grant Wooldridge was nice enough to take the time during the install to explain how to install, remove, sharpen, shim, etc... so that I can inspect the impeller and do simple maintenance on it myself.
dogwood
05-15-2005, 05:56 PM
reelfine -

Thanks for the post. I too have a 115 4stroke on a 19' scout. Love the fuel economy and not having to mix oil/gas. But with the 4 stroke, you really sacrifice quickness. I often wondered about a stainless impeller. I think I will look into this some more.

-Craig
5 Salt
05-15-2005, 07:26 PM
I wonder if same is available for Yamaha F90 Jet?
reelfine
05-15-2005, 09:01 PM
I don't know, but if I were you, I would give Wooldridge a call and ask. I know that there is some sort of cutoff point where it just won't work period, but I don't know what that is (and I forgot to ask).
No Luck
05-16-2005, 08:55 PM
What would be the difference between aluminum and stainless be in a jet just less flex our what? I have a 130HP Honda on an 18 foot North River flat bottom sled.
reelfine
05-17-2005, 09:17 AM
The main difference is that a SS impeller has 4 blades instead of 3.

Aside from that, SS is a more durable material, so it doesn't tend to nick or wear as badly as an aluminum impeller.
No Luck
05-17-2005, 06:30 PM
Reelfine

Do you think it would make much difference with my 130 Honda?
porter
06-19-2006, 08:21 PM
I know I'm bringing up an old thread. There is one testimonial that a stainless steel impeller is worth the expense. Has anyone else made the conversion. I have a 150 hp power head = 105 at the jet.
dogwood
06-20-2006, 10:53 AM
I did it and noticed a difference on my 4-stroke 115. It still doesn't compare to the hole shot of a 2-stroke but it is an improvement.

Craig
reelfine
06-20-2006, 11:18 AM
I'll add in that this was in an unloaded boat with just me. Adding people does bog it down significantly. I still feel the SS impeller was a worthwhile investment and would do it again, but there is no doubt that a 4-Stroke jet cannot compare to a 2-Stroke jet. If I were to do it again, I would go 2-Stroke.

I'll also add that according to Wooldridge, the SS impeller was developed for the "big" motors (150hp) and above. The effect on an inline 4 is a bonus, but your biggest gain will be on the 6-cyl. motors.
dogwood
06-20-2006, 05:19 PM
I'll add in that this was in an unloaded boat with just me. Adding people does bog it down significantly. I still feel the SS impeller was a worthwhile investment and would do it again, but there is no doubt that a 4-Stroke jet cannot compare to a 2-Stroke jet. If I were to do it again, I would go 2-Stroke.

I'll also add that according to Wooldridge, the SS impeller was developed for the "big" motors (150hp) and above. The effect on an inline 4 is a bonus, but your biggest gain will be on the 6-cyl. motors.


:yeahthat: I found the exact same to be true. I would also go two stroke or at the very least go to the 150 4-stroke with the stainless impeller. If it wasn't for the fuel economy of the 4-stroke, I would definately go 2-stroke.

Craig