major speed issue

[MarsPA]

I posted this in the tracker section of bassboat forums in the top speed section....then just found that there's an actual "props" forum, so I'm copying here to see if I can get some more insight or recommendations:

2016 Tracker TXW 175, 20HP Merc Fourstroke....top speed 7.5mph!!! Whoooohooooo!!!!!!

I bought this boat from a seller telling me he got just over 20mph with the 20 horse...I was happy to hear that. Turns out, with a half tank of fuel and no one with me, I'm getting 7.5 in good conditions. A more comfortable cruising speed at 3500rpm is about 5. We have a 20hp restriction in PA on most small lakes (including the one I'll spend 90% of my time on), so upgrading to a larger engine isn't a possibility. Can anyone advise anything that may help. Even if I could get 14-16 would be a huge improvement.

​Dharr had given me some advice to check for a spun prop, which I'll do next time on the water... That would be a great easy fix if I'm lucky enough that that is my problem, but I'm guessing that i just have an issue of an underpowered motor for the boat, so I'm hoping to replace the prop (whether the hub is spun or not) and see if I can get the boat to move at all. 6 mph moving down the lake is unbearable.

I currently have what I assume is the stock 3 blade prop, the only print on it says 10p (I assume 10 pitch?), and i measure the radius of the prop to be 4.5" making it a 9" diameter (though I could be off and it's a 9.25 or something...tough to measure accurately). I've read that a 4 blade is better for underpowered motors pushing heavier loads (my boat is, I'm guessing, 1600 lbs on average with people and gear, plus engine and fuel....21 gal tank that I'm trying to keep at 1/4 full, though that hasn't affected speed at all). I also read that a higher pitch will improve top end speed, but the props I've found that seem to be recommended for kicker motors (again, underpowered for vessel) seem to be 4 blade 5 or 7 pitch. I'm new to this, and the prop thing is confusing.. Any advice would be appreciated. I'm currently looking at a Solas Amita 4 10" prop with 5 or 7 pitch (is the best guess I'm coming up with), PN 5113-100-05 or 5113-100-07....but the Solas website is not showing that 4 blade as an option, so I'm wondering if the 10" won't fit. They are recommending a 3 blade 7 pitch (stating a 6 pitch is preferred but they don't have one) in 9.25 diameter.

Also, possibly worth mentioning (and supportive of a spun hub theory) is that I get 5.5ish mph at 3500rpm, then at WOT I'm only gaining 1-2 mph (topping out at 6.5-7.3 mph). Not sure what that WOT rpm is, but I'm guestimating 5500 or so (the motor is rated to be WOT 5400-6100 rpm). I'll check that RPM for sure next time on the water.

I'm REALLY hoping that the final answer to this isn't "I'm screwed...live with 7mph". The guy who sold me the boat claimed 20-22mph, but I'm sure not seeing it. The bow never lifts and I just trudge through the water.

Thanks for any advice anyone can offer.

[21XDC]

I'd try a prop with more blade area... Like what a pontoon boat uses. That is a lot of load for a 20 hp motor. Sounds like it's slipping instead of pushing. A splitfire is what I'd be looking at if they offer the pitch you need and fits your LU... https://www.boatpropellerwarehouse.c...r-48-8m8026650

I'm not sure if this prop fits or if one is offered that does.

[skennedy]

I have a 25 mercury 4 stroke I v been using for years and it pushes heavy loads of decoys ,gear ,dog and two guys no problem . Those motors run so quiet and smooth if it’s not you may need to have it checked out . Sounds like it s running on one piston .

[Dubee]

How fast did it run during the test drive

[AllyFishing]

^^^^^haha......I know where you're going with this!!!

[AllyFishing]

https://www.trackerboats.com/boat/motors.cfm?boat=4569

It lists the average speed of a 25HP at 23-25 MPH. It does not list the speed of the 20HP. so based on that I'd say 7MPH there's something wrong

[21XDC]

Not necessarily. If the boat could plane off, I could see the gain in speed. He’s just not getting the boat up on plane.

[MarsPA]

21XDC....Thanks! i'll look into that, it fits what I was thinking on going to a four blade, and it's a little smaller than the 10" Solas (which is why I'm guessing Solas doesn't list theirs for my motor)...I just wish that one came in a lower pitch than the 9.5 since what I have on their is a 10. Much appreciated.

I'll contact Spitfire and see if they may offer that in other pitches.

[MarsPA]

skennedy.... I don't think that's the case....it sounds quiet and smooth, it's just doggishly slow. Before I took the boat on the water I took it straight to my marine mechanic to have him go over everything, and he thought the motor was fine....but that was in shop, he couldn't put it in the water.

[MarsPA]

How fast did it run during the test drive

Thanks Dubee....also super helpful. I invite you to try to test drive a boat in Pennsylvania in February next time you're up here. It's a 2016 boat in excellent shape gone over by my mechanic. I did the best I could.

[skennedy]

It sounds like no power to me when it’s under a load . take it back to your mech and have them hook it up to there Dyno The problem should show it’s self there . Those little 4 strokes have a ton of low end in them your not getting power to the prop .

[skennedy]

I have three props for mine I have one of the smallest S/S props that I don’t use that I would sell at a reasonable price if you hav3 to go that route. I think it’s a 9.5 pitch

[MarsPA]

Thanks Dubee....also super helpful. I invite you to try to test drive a boat in Pennsylvania in February next time you're up here. It's a 2016 boat in excellent shape gone over by my mechanic. I did the best I could.

You may be right on this.... I got to the lake yesterday and found that my WOT is lower than I was guessing. I was at 5.35mph at 2850rpm, 6.9mph at 4200 rpm (feels like half throttle), and 8.05mph at 4600 rpm which was my WOT. 4600 is well below the 5400-6100 rpm range shown for the motor.

[skennedy]

So if your getting the motor up to 4200 and only moving at 6 mph woundering if you haven’t spun a hub . I’m really not sure if those smaller props have a pressed in rubber hub .

[smoken86]

Does that little 20hp have power tilt? I remember something with a little tin boat when I was younger that I don't know if would even matter with this motor.
A buddy had moved the pin for the stop and wasn't trimming all the way down and we couldn't get on plane to save our ass.

[MarsPA]

So if your getting the motor up to 4200 and only moving at 6 mph woundering if you haven’t spun a hub . I’m really not sure if those smaller props have a pressed in rubber hub .

I marked the hub before I went out yesterday, and i think the results tell me not spun....but I'm not positive. The mark was slightly off of where it started...probably 1/8". I assume that's acceptable range of movement (or is there zero movement acceptable). Also...I'm assuming that the total movement was 1/8". I guess there's always the possibility that it turn 1000 full circles and just landed 1/8" off of it's starting point. Every broken clock is right twice a day.

[MarsPA]

Smoken...It does have a power trim. i'll look to see if it can drop any lower, but it seems to me that it's getting pretty far down. I need to read some on trimming the motor, I honestly don't really understand it. I generally just start with it all the way down....but I've also tried starting with it up a little and lowering the motor as I get going. No real difference at these low speeds. I'm a rookie.

[chatabass]

The one experience I had with a spun hub, it would idle just fine but when the power was increased it would break loose before the boat got up, the RPM's would shoot up while the boat slowed and sat back down. This was on a 110 HP motor I don't know if horsepower would make a spun out hub behave differently.

[slotcarracr]

how many splines are there on it 14? put a 11 pitch on it part number 5111-093-11 solas the problem is there is no way you will ever get the boat up so there is not alot of slip from the friction

[nikldac]

I have a 2008 Tracker Pro 170 with Yamaha 20 hp 4 stroke.  Original prop was 8p which would only run around 7-9 mph. Dealer let me try a 9p stainless steel Solas and it ran 17 mph with just me in it. Now when I had a partner with me and livewell was full....it would only run 7-9 mph. Even at 17 mph, I could never get it on plane. Originally, the boat had a 40 hp Merc on it that I couldn't use for small lakes, so I traded down to the Yamaha. The Yamaha did have power trim...which didn't have enough power to trim while the boat was running.