2001 2 stroke 15 Mercury

My 15 hp merc has a 9x9 prop now, on a 15.5' open v tinnie, total weight is never more than 900-1000 lbs with the largest load.

new to me set up, last summer

I'm thinking I need a prop with more pitch (there is a 9x10 1/2 listed for this motor) because at around 7/8 to full throttle (maybe less than 7/8) the motor speed is the same to my ear. So I usually run it less than WOT

I know I should put on a tach and check out WOT rpm's, and will do that this spring .

But I was wondering if anyone here has the same motor on a similar light loaded boat, and if you use a 9x10 1/2 or a 9x9 prop on it.

It just seems to be a little under pitched to me

I think about these things now, when it's still winter, and am looking forward to getting out in the boat again haha.

thanks for reading and any input

Well I don't have the same motor or boat but I have a 87 15hp johnson with a 9.5X10 on it and on my 14ft tinnie V hull she does real good up to about 1000lbs and not to much after that I cant get it on plane. I usually run with 750-850lbs and the motor does well but could probably do better with a 9X9. You won't gain much speed if any going up just one pitch. I bet your running the correct prop. I have thought about putting a 9X9 on mine so that I could plane with my wife and both kids in the boat but decided to just put a larger motor on. I highly doubt you are running over the WOT recommended RPM and you will drop a couple hundred by going up in pitch.

thanks for the reply

here's the prop chart from the manual that got me thinking about a prop change.


Propeller Information Chart -15 HP
Wide Open Throttle RPM: 5000-6000


Typical Gross
Boat WGT.
(LBS)
Typical Boat
Length
Speed
Range
(MPH)


prop weight length speed mph
9x 10-1/2, Up To 1000lb Up To 16' 18-28
9x 9, 600 – 1500lb 14' - 18' 14-24
9x 8, 800 – 2400 15'- 20' 15-25
9-1/4x 7 1000 – 3400 16' - 22' 8-18
9-3/4x 6-1/2 1800+ High Thrust Reverse

I'm using a 9x9 now.

This is the first Merc I have owned, and the revs just seem a bit high compared to the OMC motors I've ran in the past.

I'll just have to wait to see what the rpm's are now, to see if it's worth the change.

LOL it's snowing today, so it'll be a while!

Well it looks like you have the correct prop on already unless you run with less than 600lbs most of the time. Chart looks about correct, being that it shows over 1000lbs being to much for a prop like I have on mine. I think my max RPM on my Johnson is 6000- 6250 though. I am lucky to hit 4500-5000 RPMs with 1000lbs or more though.

We also got 6 more inches of the white stuff last night here I am itching for the weather to break and the spring pike bite to start.