Concerning PT175TXW performance

[Philobeddoe]

Hello Folks! Long time reader, first time poster.
I bought a used 2010 PT175TXW that came stock with a 2-stroke 90 Classic Mercury (There was only a year or two span that this hull was 90hp rated). I upgraded the TM to a 70# thrust Motor Guide X5 (just before it was discontinued) and added one more battery to the existing two. I weigh approximately 200# and carry about 150-200 lbs of fishing gear, ice, tools, etc. I replaced the existing 19p Solas aluminum prop with a 20p Power-Tech NRS stainless three blade that I borrowed from the local outboard repair shop. After running it for a couple of days, I was very pleased with the hole-shot and handling, but I was a little disappointed with the speed. My best speeds were between 40-41 GPS @ around 5500-5600 RPM. When I returned the Power-Tech and told the mechanic about the boats performance, he said that a top rpm of 5600 was lugging the motor and that he would get his prop guy to make a recommendation. That recommendation resulted in me purchasing a 17p 4-blade Power-Tech. With the 4-blade, my top end speed decreased to 38-39 GPS @ 6000 rpm and the handling was horrible (had to trim WAY down to get grip in the slightest turns). After some research, I found out that Mercury Marine recommends a top RPM of 5600 for my particular model motor. I have since tried a 21p P.T. NRS and could only turn it 5000 RPM.

With all that being said... I'd like some advice, set-up tips, etc. from any of you that has time and don't mind sharing. I'm not currently running a jack plate but I'm definitely open to it. The motor is mounted second hole from the top.


Thanks in Advance!!!

[Extremeboating]

Are you intent on using a powertech prop? You may want to take a look and swing for Mercury's 4 blade Spitfire X7 prop. The only props which are faster than those apparently are the Yamaha 4 blades but those won't work for obvious reasons.

I think your issue may not be RPM, but physical design of the prop which is causing you speed loss. With a 90 you should be running 45-48 mph I would think. Especially with a 2 stroke which should weigh considerably less.

Your boat would benefit from a nice 6" jack plate for sure. I'm also curious as to what hole you have your motor mounted on?

EDIT: I just checked out your setup based on the info your provided using the 20 pitch Powertech prop as reference. It appears your top end speed should be about 45mph as I indicated, and what is being recommended is a 21 pitch prop in a 4 blade for the Spitfire X7 or the Trophy Sport. If I were you I would stick with a Merc prop for a Merc motor. Nothing is going to be designed for it to work better for it than a product designed specifically to work with it.

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[Philobeddoe]

Thanks for the response! I'm definitely not dead set on using a Power-Tech. I could probably trade both of my Power-Tech props on a Spitfire and a manual jackplate without having to fork out too much cash. Any recommendations on a particular brand jackplate. I doubt I go hydraulic simply because of price.

[Extremeboating]

I can't speak for your situation, of course because I do not know the type of waters you run in but a hydro jackplate would help get your trim and height levels absolutely perfect on the fly without ever having to work with hoists or remove of bolts or loosening this and retightening that.

If going Manual, however, you have your choices open, but I have not heard any bad things about the TH Marine manual CMC plate.

As far as the prop goes, make sure it is the Spitfire X7 and not the standard Spitfire aluminum.

If you change your mind and go hydraulic, I would recommend a Vince mini hydraulic jackplate. I paid about 1000 for mine and there was no wait time or lead wait time (plus support is excellent) for it unlike Bob's Machine Shop jack plates. Their stock is non existent right now and their support is horrid in my experience. Come to think of it, if you want a manual jack plate, I would have no issues at all recommending you a Vance one as well. They may even be cheaper than the TH Marine CMC one.

[Philobeddoe]

Thanks again for the recommendations. I'll definitely be going stainless regardless of which prop I end up with. Just for kicks (using the Mercury Prop Finder calculator), I ran the numbers using the 17P at 6000 rpm and was recommended a 12.7" x 19P Spitfire X7 and a 13.5" x 20P Laser II. Got the same exact recommendations when I ran the numbers using the 21P @ 5000 rpm.

[Extremeboating]

You are going to have to base it upon what the spec RPM range is and you are want to be on the hotter side and then based upon how it ran at decent RPMs and performance then take those numbers and run with that. I wouldn't advise using your data with a different prop that put you outside of range. Especially because propellers are as expensive as they are.

[Philobeddoe]

Gotcha. I ordered a 6" Vance yesterday afternoon.

[Extremeboating]

Gotcha. I ordered a 6" Vance yesterday afternoon.

Very nice. I take it that it was fairly cheaply priced? I just had a maintenance day and switched out to a 4 blade trophy sport prop yesterday. I'm itching to go try it out and see what improvements it made.

[Philobeddoe]

$190 for 6" manual

[bassfisher444]

90 hp Optimax here, all I could get out of it stock with no Jack plate and a cupped 22" pitch laser 2 prop was 42mph, added a jack plate and I could get 43 mph, converted it to a 115 and I could get 44-45 with the same laser 2 prop. I am now running a 22" pitch Powertech PTR3 with No jack plate and the motor in the 3rd hole and I can hit 46 mph. Your 90 HP 2 stroke has a 2.30 gear ratio and a max recommended RPM of 5500 hundred although it won't hurt anything to turn a couple hundred RPM more. I would keep that 21" pitch Powertech NRS 3 it is the correct prop for that motor and far better than any 3 blade Mercury prop for that size motor. You could try moving the motor up to the 3rd hole from the top, I gained 2 mph by doing that, the jack plate will work well, start at 5.5" prop to pad and see how it does, you can't run the 3 blade props high on these boats like they do on the fiberglass boats with larger motors. Also I would get a new boat mechanic because he clearly doesn't know what he is talking about.

[Extremeboating]

90 hp Optimax here, all I could get out of it stock with no Jack plate and a cupped 22" pitch laser 2 prop was 42mph, added a jack plate and I could get 43 mph, converted it to a 115 and I could get 44-45 with the same laser 2 prop. I am now running a 22" pitch Powertech PTR3 with No jack plate and the motor in the 3rd hole and I can hit 46 mph. Your 90 HP 2 stroke has a 2.30 gear ratio and a max recommended RPM of 5500 hundred although it won't hurt anything to turn a couple hundred RPM more. I would keep that 21" pitch Powertech NRS 3 it is the correct prop for that motor and far better than any 3 blade Mercury prop for that size motor. You could try moving the motor up to the 3rd hole from the top, I gained 2 mph by doing that, the jack plate will work well, start at 5.5" prop to pad and see how it does, you can't run the 3 blade props high on these boats like they do on the fiberglass boats with larger motors. Also I would get a new boat mechanic because he clearly doesn't know what he is talking about.

That's a trip. With a 90HP motor especially converted to a 115, that 175 boat should SCREAM on the water in comparison to it's OE equipped counterpart. You should easily be able to achieve 50-55MPH out of that thing.

[TDJ2591]

I’m getting 40-42mph at 5,500 rpm on my PT175TXW with a 75hp 4 stroke and the stock 13-1/4 x 17 Black Max aluminum prop. That’s with a full tank of gas, 3 batteries, fishing equipment and me @200lbs. With 2 200# men I’m getting 39-40 mph.