20 HP outboard ques?

[basadochi04]

I have a 1973 mercury 200 20hp 2 stroke and I am wanting to know what would changing the prop pitch from an 11" to a 9"? The 11" that is on it is a 2 blade and the 9" is a 3 blade does this matter? I am just wanting to get my 14ft. john boat up on plane faster. Daddy told me I needed to get a bigger motor like a 25 or 30 horse, but this motor was bought brand new and kept in really good condition by my grandpa and it runs very well. any help would be appreciated

 

[rndn]

Re: 20 HP outboard ques?

A 3 blade will help get it on plane better than a 2 blade. You really should not drop in pitch by 2 inches unless you know what your outboards rpm's are at wide open throttle. Your motor was designed to run in a very specific rpm range and changing the pitch without knowing what you are currently running could do damage to your motor. If you don't have a tach see if a marina that selld props will check your motor for you so you know if you need to stay with the same pitch, increase, or decrease.

 

[rndn]

Re: 20 HP outboard ques?

By the way, Welcome to the forum!!

 

[steelespike]

Re: 20 HP outboard ques?

Does the boat struggle to get on plane or do you just want it to be quicker?
What kind of load?
Is the throttle opening all the way?Does it seem to go well once on plane?
Have you tried trimming in a notch?Moving weight forward will help.
If you could get a GPS speed reading that would help some.You might want to do a compression check.

 

[basadochi04]

Re: 20 HP outboard ques?

It struggles to get on plane but once on plane it will move pretty good. I have moved the battery and the heavier anchor to the front and it still has a little trouble even with my brother up front. I am pretty sure the compression is ok because my dad put new rings in it a few years back. If I drop down to a 9x10p quiksilver aluminum prop would that mess with the revs to much? I just want it to get on plane easier and maybe just a little fast without having to buy a new motor. I like my antique Merc.

 

[steelespike]

Re: 20 HP outboard ques?

If It struggles with the 11 give the 9 a try.It should jump on plane It will run
about 400 rpm higher.Just be aware it may be maxing the rpm.If it is a bare bones 14 Jon I would think it could get it up pretty good with the 11 with one aboard.If you ask a marina if they could just check your rpm with the 9
they might for a reasonable charge.