johnson 115 prop

[cheyanne]

Hello to all.
Once again looking for all the help and advice for this newbie here.
Had a few issues with the idle of the johnson 115, and after reading and getting advice from various members I got the 115 running and idling very well. Runs very well now
There is a bit of a water leak from one of the hoses where it is spilt but that is an easy fix.
So to my question........
The prop......
Reading all relevant data I should be getting between 4,500 and 5,000 RPM , but I only manage to get MAX 4,000.
It takes an age or more like forever to get up on to plane, and even then I really don't think it is right up. The trim is right down and I try to adjust slightly but still no extra revs..............
Speed......well maybe about 18-20 mph, according to the GPS.
From what I can see on the prop I see the following.

On the outside I can see 2210 stamped in between 2 of the blades.

On the shaft connection where the prop is bolted on, I see.... 13 3/8 x 17"

I think I should be getting at least 5000 rpm and speed of at least 25 maybe 28mph.

It is a 3 blade prop, alu. Has I admit seen better days. Maybe replace but what with???

I would welcome any and all suggestions and advice,

Thank you

 

[86 century]

Re: johnson 115 prop

I cant find that number.

The 13 3/8 17 is the diamiter and pitch.

 

[steelespike]

Re: johnson 115 prop

We need to know the year,brand,style and size of boat, year of the motor.
I can tell you that 15" and 17" are typical size of props for that motor in typiocal applications
it is intended for. 16-18 ft. Pretty sure your not on plane Can't be sure about you possible max rpm till you get it on plane
One or 2 people added at the bow might get it over the hump for an indication of its true max speed and rpm.
It's very likely you still have a motor issue.
The boat could have problems as well.Perhaps it has absorbed a load of water or a dirty or rough bottom?

 

[cheyanne]

Re: johnson 115 prop

Ok.......
It is a 1973 Mako 19. Center Console with t top.
The motor I believe is 2001 Johnson 115..........Just changed the 2 water hoses I mentioned this evening
When we do 'appear' to be up on plane full throttle is topping out at 4000 rpm. But it just takes so long. ( going to rename it Sea Slug)
We did try a body up front and whilst it was ok the rpm never went over 4000, (maybe a whisker)
Looks dry inside insp hatch at rear.
Bottom feels reasonably smooth, not very, but certainly not lumpy.

 

[steelespike]

Re: johnson 115 prop

Near as I can tell your boat is about 1500 lbs A 17" prop would be normal and rpm close to the 5,500.
I think you have issues other than a prop.Boats of similar soze sometimes produce speeds approaching 40+.
Slowest I saw was 2200 lbs and ran a 15" prop at 5850 (newer motor)36 mph.
If your not quite on plane a 15 might get you on plane and assuming it turned 5500 make speed about 36.
But in my opinion the 17 should plane well and turn around 5500 and 40 mph.
If you are on plane then a 15" prop is only going to add 300 to 400 rpm. And if you go any lower you'll be in pontoon prop territory.
I think you need to check the motor; could be as simple as missing a cylinder.