Suzuki DF25A Propeller Experience

jtsull

First post.  Like to share my experience changing the prop out on a 2018 DF25ATL.  I sorta tricked out a 14' Tracker Grizzly with a new DF25A, micro-jacker, side console and beavertail pods.   After break-in I was getting about 27 MPH but the tach was over 6200 RPM so I decided to get a SS prop and jump up from 10 pitch to 12.  Reading numerous posts from various forums and articles, I read you lose about 200 RPM / pitch when going up in pitch.  So 2 pitch changes may get me to 5800/6000 and maybe faster??  I installed it and what a mistake.  At idle speed up to 2000 RPM the engine vibrated badly and there was some sort of clicking coming from the transmission.  At full throttle the RPM were down to 5600, the engine seemed to be laboring and I lost top end down to 24-25 MPH.   I worried I bent the shaft by tightening too much.  Got it home.  The prop seem to rotate fine with no deviations.  I pulled it off and installed the original prop back on.  Back out on the water everything is back normal.  No vibration, no strange noises from the lower end. 
I think the moto to the story is don't mess with small engine props.  Can't compare the results to the big ones.  Not sure if I just got the same size/pitch in SS the results would have been more favorable.  Shell shocked now to try... 

Alex from GA

You need to have the stainless prop checked for balance and pitch.  Someone might have dropped it somewhere.  Also have it repitched one size less to get it in the proper RPM range.  I might be too big in diameter.

RiverRat22

Exactly what props did you use?  Not all props are designed the same, so there's a lot more to it then just the pitch number.

Did the stainless prop have a removable hub kit?  A lot of those are known to have some "prop rattle".  I wonder is that is the noise you are talking about.

jtsull

Thx for the replies.  The engine came with a 10 1/4 x 10 aluminum prop.  Because it was topping out above 6200 RPM I thought more pitch is justified.  I bought a Solas 10 1/4 x 12 ss prop.  So the diameter did not change - just the pitch and whatever effect changing to a SS does.   Perhaps the new prop was badly out of balance.  The noise I was hearing seemed to be on the top of the lower end.  Between the powerhead and lower end.  Once I reinstalled the original prop and tested it again in the water, no more strange noises or bad vibration.  
I wonder if I just went with the same spec prop in SS would I have gained anything?   Obvious difference is the SS prop is quite a bit heavier.

snookaffinity

The stainless in the same pitch should lower you RPMs some. Isn't 6000 the specified high RPMs for that motor?

RiverRat22

Solas props run steep, so what you have there is more like a 13-14 pitch.  I've never head of a prop causing noise from the midsection. A 10 or 11 Solas is probably a better fit.  Don't be afraid to call these prop companies before you buy, a lot of them have people there to help you pick the best prop for you.
A 25hp motor is going to be very sensitive to weight so make sure you are doing your testing with the load you will be using most often.  You might be at 6200rpm by yourself, but another person in the boat could put you right at 6000.
Performance wise, on a low hp boat, stainless and aluminum will perform about the same.  The durability of stainless is the big difference if you run shallow a lot. 

jtsull

5600 - 6000 is the recommended range.  I'm a little beyond that so I thought I would be smart. 

I agree RR22.  Yes, that is with me alone and the motor raised and trimmed for max speed.  (I have a micro-jacker).   
Thinking I'll just hold off until I bump something running swallow and need a prop rather than want one.....