need help with choosing prop

[55evinrude]

Hey everyone! I just got my new 2011 Mercury Sea Pro 25hp outboard and a 2012 16' Ultracraft! I am in need of choosing a different prop than the one that comes with the motor. the boat weighs 280 LBS and the motor 110 LBS so about 330-340 with gear and fuel. sometimes it's only me in the boat so add 160 LBS but sometimes there is up to 750 LBS of people and other things in the boat.

So with just me in the boat and the gear including the boats weight: 500 LBS

with an average amount of weight in the boat including the boats weight: 1100 LBS

the current prop I'm running is 9.9 diameter by 11 pitch 3 blade aluminum!
(going by sound the motor is reving to high)

Mercury's prop suggester on there websites suggest 13 pitch with 10.375 dia 3 blade aluminum
or 14.5 pitch with 10.25 dia 3 blade aluminum for the amount of weight im running.

What do you guys think I should run? sorry im new to selecting props

Nathan

 

[pootnic]

Re: need help with choosing prop

Your going to need a tach(google tiny tach),gps speed and boat style will help us also.
That being said,I don't think your to far off with the 11 pitch.
You may be able to go higher when by yourself but I think the 11 would be close if any weight added.

 

[55evinrude]

Re: need help with choosing prop

thanks for the reply. I am already looking at the tiny tach i just have not ordered it yet! and i will gps the top speed soon. I'm thinking that i might try a 13 pitch and if its not as good i might stay with the 11 pitch. also the boat is a 16' basic aluminum with a 25 tiller ( i will post pics) . once again thanks

Nathan

 

[steelespike]

Re: need help with choosing prop

A nice big 16 ft. if you can get us a carefully setup wot gps speed we can get a rough idea of your rpm.

 

[pootnic]

Re: need help with choosing prop

I have know idea on this other then what I've read and youtube but some people say removing the resistor plate behind the carb will bump the hp up to a 30.Again DON'T try this just because I said it but might be something to look into.
Nice boat and motor combo...boat kinda looks like a crestliner utility.

 

[55evinrude]

Re: need help with choosing prop

I am planning on gpsing the top speed this weekend. and pootnic I know all about the restrictor plate I ordered the 30hp gasket already and am removing the plate this weekend, i also think i will have to re adjust the timing but i am working with another member on this forum (Sea Rider) on figuring it out!

Thanks I also think it does look like a crestliner. It's a very heavy duty boat and can carry up to 1250 LBS rated for 40hp but the 25/30 seems like enough

Nathan

 

[steelespike]

Re: need help with choosing prop

We had a new bare 18' Crestliner utility in 77 with an old Gale 25 on it. It would plane easily with 6 adults.
And we did ski with a 100 lb adult spotter. No special props or setup.
Wish I knew then what I know now.It's still in the family with a 88 50 tiller Evinrude now.
the big footprint of that relatively light 18 really helped the 25 do well.
I'm sure your 16 will do the same.

 

[55evinrude]

Re: need help with choosing prop

yea my 16ft planes pretty good with lots of people in it also. but i would just like to get the correct prop to keep the engine running at the correct rpm's

Nathan

 

[55evinrude]

Re: need help with choosing prop

UPDATE: well i had the boat out today and i took the gps. With just me in the boat and with the trim set right it went 32mph and with 3 people in it and a couple things it went 26mph. What do you guys think? Do i need a bigger prop as it seems like the motor may be reving a bit to high? Maybe try 13 pitch. Anyways thanks!

 

[pootnic]

Re: need help with choosing prop

Is anything changed from the first post?
It seems like a nice speed both alone and with a load.
If it is a 11" pitch that your using now maybe that will be the better prop with a load and a 13" might be better by yourself or lightly loaded.
We could get a ruff idea of WOT rpm's using your numbers giving but that tach will tell you what prop is best for sure.

 

[steelespike]

Re: need help with choosing prop

If your running an 11" prop at 32 mph; unless your slip is extremely low your over 7000 rpm Ouch!
I guess the motor doesn't have a rev limiter.
6000 is the max.Of course using speed to determine rpm isn't the best. You really need that tach.
Just going on your research it does seem a 13 is in order. I sure would stay away from wot till we verify the rpm.

 

[jimmbo]

Re: need help with choosing prop

UPDATE: well i had the boat out today and i took the gps. With just me in the boat and with the trim set right it went 32mph and with 3 people in it and a couple things it went 26mph. What do you guys think? Do i need a bigger prop as it seems like the motor may be reving a bit to high? Maybe try 13 pitch. Anyways thanks!

Is this with or without the gasket/restrictor plate mod?

 

[55evinrude]

Re: need help with choosing prop

this is without the mod. I have not done anything to the motor it's still bone stock at this point.

Nathan

 

[55evinrude]

Re: need help with choosing prop

UPDATE: got the tiny tack installed and got 5800-5900 at wot 32mph with jjust me in the boat so approx 500 lbs including gear and boat and motor. So i guess i do not need a new prop thanks guys!