Prop for 25 hp Merc on Tracker pro 175

[kamper]

I have a 2003 25 hp Mercury 2-stroke (2.25 gear,5000-6000 rpm) on a 2002 Tracker pro crappie 175 the guy I got it from stripped the inside so it just has an open floor the motor is a tiller handle. I'm looking for prop so I can get in the upper end of my rpm range. Right now I'm running around 5200 rpm's (tiny tach) and 22 mph (gps) with lots of slip 20 some percent. The prop I have is a Mercury prop #QA2106R P13 10.38 inches.
This last weekend I built a jack plate and raised the motor 2 inches to get the motor closer to the proper height but with the added height and the prop I wasn't able to adjust the trim pin to the middle and have the prop still bite. So my numbers were around 5100 and 21 mph. The motor still needs to go higher I have water coming up the front of the motor but with the prop I don't think its possible to go higher and still have it bite in less its trimmed all the way down.

I would like to go to a SS prop is possible. Any ideas on props and pitches that would possibly work with my set up on an under powered boat. I'm not in a hurry so I'm not worried about going faster than the low 20s. Just would like to have less slip and proper end of the rpm range.

 

[steelespike]

Re: Prop for 25 hp Merc on Tracker pro 175

Where is the anti vent plate in relation to the bottom?
According to 2012 specs the boat is over 1000 lbs and rated for a 75. Needless to say a 25 is way outside the package. Which I think would account for some of the slip.
Perhaps something about the bottom or on the bottom is disturbing the water in front of or near the prop. Just to clarify the prop is a 10 3/8 X 13?
I think you need about an 11" prop to get closer to the max rpm.
Consider a 4 blade, though it might eat up some top end might require a 10" pitch.
Usually manual trim one notch isn't quite enough and one more notch is too much.
You could buy or make wedges to make half a notch possible.

 

[kamper]

Re: Prop for 25 hp Merc on Tracker pro 175

Yes the prop in 10 3/8 x 13 and aluminum. The bottom of the boat has a slight v in it and the anti ventlation plate is about 1/4 of an inch below the bottom of the v. On the right side of the v the bottom is bent up some, looks like it hit something at one time maybe a 5 inch area is affected maybe an 1/2 inch hook. Is there anything that I could fill it with? Would the hook in the bottom affect the prop when it was 2 inches lower?

I'm guessing the boat is a little lighter that 1000 since all of the interior as been stripped but its still way under powered.

 

[steelespike]

Re: Prop for 25 hp Merc on Tracker pro 175

The dent in the bottom could be acting like a trim tab making the boat lay down too much.Perhaps you could press the dent out somehow a rig a brace to keep it out as it might "oil can" (pop back in).If the dent is all or partially in front of the prop it could cause problems.
Is the prop in excellent condition?Its Usually suggested that the plate be visible at speed not necessarily above the water but
very close.Of course this could vary depending on the boat and motor.
We had a 18 ft Crestliner Voyager utility. About 375 lbs dry.With an old Gale 25 it would plane easily with 6 adults.
Easily about 1000 to 1200 total load. This was with no special setup or prop selection.
The reason it did so well was the large foot print helped it get up on the water. And of course the relatively light hull
helped as well.
You do have the advantage of the large foot print unfortunately its a little heavy to start with.
Might be interesting to weigh the whole thing.Scrap yards usually have a scale and will weigh for a small fee.
A 4 blade prop will resist venting have good hole shot, stay on plane easier at reduced throttle,seem smoother and
respond better around the dock.

 

[kamper]

Re: Prop for 25 hp Merc on Tracker pro 175

I think the dent is acting as a trim tab. The boat does best with most of the weight in the back. I will see if I can push it out. It's right at the transom weld line so I don't want to mess up the weld.
I can only find one 4 blade prop that is SS and 10 pitch and it's a power Tech. Any one know of any others that will fit a 25 merc

 

[kamper]

Re: Prop for 25 hp Merc on Tracker pro 175

I was able to pop most of the dent from the bottom of the boat then I filled the rest in with jb weld to make it smooth. Don't know how long it will last but it is working for now. The boat rides different now so it was affecting the preformance.

I ended us with a power tech SRA3R11PM25 with just me in the boat it is running at around 5800 rpm and about 23 mph. I still need to raise the motor about a half inch to an inch to get it at the right height so I may gain a few rpms.

The prop preforms much better than the old one and has lots more low end power now.

 

[jestor68]

Re: Prop for 25 hp Merc on Tracker pro 175

Have you measured the height of your transom? The Tracker web site shows the 175"s as having a 22" transom height; while the 16 ft has a 21" transom.

Does your 2002 model have a shorter transom?

 

[kamper]

Re: Prop for 25 hp Merc on Tracker pro 175

I just tried to measure it but I'm not sure of the proper way. Depending on how you measure you can get 21 or 22.

 

[jestor68]

Re: Prop for 25 hp Merc on Tracker pro 175

That's interesting. With a 20" shaft motor, you AV plate should be above the keel by 1 or 2 " with the motor mounted down on the transom. There should be no need to raise it at all.

Do you plan on doing water sports with your fishing boat? There are plenty of 3 blade SS props that will get you more top speed than a 4 blade.

 

[kamper]

Re: Prop for 25 hp Merc on Tracker pro 175

Jestor68 I got a chance to do some measuring tonight it looks like the transom is about 21 inches to the bottom of the modified v. The shaft length on the motor measures out to be 22 inches (measured from the top of the clamp where the motor sits to the AV plate) I measured my Yamaha 70 the same way and got 20 inches. I'm not sure why the 25 merc has such a long shaft.

If the motor is mounted normal the av plate would be about an inch below the bottom of the boat. I have the motor mounted on a DIY jack plate that raises the motor about 2 1/2 inches. If I remember right water rises about 1 inch per foot behind the boat. My AV plate starts about 2 foot behind the boat so I still need to raise the motor some to get the Av plate at the top of the water.

No I'm not trying to do water sports with my underpowered fishing boat I was wanting a 4 blade prop to help with my huge slip problem. The SRA prop 11p I got from power tech has a lot of cup and has got the slip down to 14% and has tons of bite.