What prop? 90 Mercury Pro Team 190Tx

[basslipripper]

hey guys/gals,

I have a 2006 Bass Tracker Pro team 190 tx. It has a 90 Mercury ELPTO non DFI. The prop that is on the boat is a Solas 3 blade stainless that is 13x21. At WOT the boat runs 6200 rpm per the console tachometer and 46-48 mph GPS. I feel like the motor needs to be at about 5500 rpm. So I was thinking maybe a 23p or a 24p. based on the common rule of thumb that there is a loss of 200 rpm per pitch increase. Any pointers??

Thanks.

 

[huntinfool]

I have a force 90 on my 1860 and I news to change my prop too. Now that I've posted this I can't for the life of me remember what it is.
My dad keeps telling me I need to go up in pitch, but the guy who rebuilds props says I need to go down. But I think my prop is too small to start with.

Don't have any advice for you on this, but I'll be watching what advice you get.

 

[driz]

The best way to find out, the very best is do this. Take your boat if you don't already know and wind it up an find the RPM's at wide open throttle flat out max. That's WOT the crucial number. Do it with a full or nearly full tank and all the gear you carry normally. Then go get the boat and trailer weighed (full of gear gas) at a local quarry or feed lot where they have truck scales.
Then you call around and see which structural steel fabricator fixes propellers. There is usually one who does it and the marinas all farm their work out to them welding / balancing props and lower units. With the weight / hp and WOT numbers he should be able to get you set up with just what you want. Often they will let you take a couple and give them a try to see which best suits you. Since they usually sell as well as repair props they can get exactly what you want cheaper than you can mail order them (my experience).
FWIW the standard range is supposed to be somewhere in the red arch of the operational WOT range of you boat . Mine is at the dead bottom on my Bayliner as I wanted an extreme cruise prop (but slow on takeoff). Up in the further end of the operational band is a motor set up more for takeoff but burns more gas and has noticeably slower acceleration. Working with the prop shop you can get it set up pretty much the way you like it by tweaking a bit this way or that. They also come in handy when you bump that prop on things . The last one I had straightened was around $80, about half the cost of a new one.

 

[basslipripper]

Thanks for the advice

 

[muskiemike12]

Here is a test from the mercury marine web site. https://www.mercurymarine.com/engines/engine-tests/boat-house-bulletin/?ID=1247& I'm very surprised that your wot rpm's are that much higher. You may need to verify that your tach is reading correctly.

 

[basslipripper]

Thanks... My motor is carburetor non fuel injected. As of now Im running a solas stainless 13x21. where the test shows a black max aluminum 13x19. which would explain my slightly faster speeds. But I still have almost 500 more rpm's. My hole shot is super quick less than 2 boat length. So I figure I can go up a prop or 2 to for a little more top end with out killing the hole shot. Id like to see 50+ mph. I have already moved the motor up one set of holes so about 1.5". I noted 2 mph gain from that. This boat does have the revolution hull. I think a 23p-24p trophy would put me up over 50.. There are a few 190's floating around that are breaking 55mph. I just want 50 mph...

 

[basslipripper]

The newer revolution hulls are pretty fast for an aluminum boat. My buddy has an 19ft express with a 90 yamaha and my boat is significantly faster.

 

[muskiemike12]

I just ran your numbers through a prop slip calculator https://www.go-fast.com/Prop_Slip_Calculator.htm and with those numbers you have 23% prop slip. That does not seem right. 23% would be acceptable prop slip for a pontoon. You should be in the 10%-6% range with that hull. That slip and rpm's would put you at 56mph. I think your tach is not reading correctly.

 

[muskiemike12]

Did you use GPS to verify your speed? You cannot trust the spedo in the dash.

 

[basslipripper]

Yeah need to check the tac. I thought it was a little high but wasnt sure that why i said per the boat tachometer. yes gps for speed.

I just ran the numbers on a prop calculator and Im getting 9% at top speed of 48 mph 21 pitch prop 2.33 gear ration and 6200 rpm gave me .092910 prop slip

 

[huntinfool]

Right now my boat does not seem to reach WOT. I can get to about 5000rpm and then the prop seems to ventilate. I can get up over 5500rpm but I do not gain any speed and I just get extra noise and vibration. I think I'll look for a 13x19 to start with and see what that does at WOT. Hopefully this will be a good starting point.

 

[muskiemike12]

You might have a hard time breaking 50mph with that lower end ratio. When I ran your numbers I used a ratio of 2. Was 2006 the last year of the 2.33 gear ratio? The 90 Merc I have on my pontoon is 2:1

 

[basslipripper]

https://www.mercurymarine.com.au/home/outboards/twostroke/90-hp-40-hp/90-hp.asp

The boat came with a 60. The orginal owner bought a new 2005 90 that had never been run from a dealer. Took the boat out yesterday. My tac seems fine. Im gonna try a 23p maybe a 24p. See what happens.

 

[huntinfool]

Post up after you do, I'm curious.

 

[WVfishnfool]

Only way to know if your tach is right is hook that motor up to a digital diagnostic (computer) device that's calibrated and check the tach against it. Most of these analog tachs are off that's why most guys are getting the SmartCraft gauge and Merc Monitor systems on the new Mercs. They're danged expensive but they're on the money 99.9% of the time. Once you verify your tach is reading correct then start adjusting motor height(keep a check on water pressure) and playing with props. Already seen you're using GPS for checking speed so you're good to go there. Have fun and be safe with it.