Flat Bottom Hull—Jack Plate—Shallow Water Project

[Ebug]

I have been on a quest to tune my flat bottom boat to run in shallow water environments and have decided to share the results for others to learn from.

Boat
2012 Tracker (Grizzly) 1754SC converted to center console
60hp 4-stroke Mercury 20” shaft
Engine mounted at lowest position.
Factory prop 14p aluminum 3 blade



Notes:
#1 This is the factory “as delivered” setup. The motor is mounted at the lowest setting. Prop stays hooked up coming out of the hole, but takes a fair amount of time to get on plane. Especially when loaded with family. Motor never reaches a safe rpm for longevity. Really poor prop choice by Tracker.

#2 Same setup as #1 with the only change a 12p stainless 3 blade Vengeance prop. Prop stays hooked up coming out of the hole getting up on plane very quick and short distance. This is what I feel is the best combination for this boat in any body of water greater than 3' deep.

#3 Same setup as #2 with the addition of a 5.5” hydraulic jack plate mounted at top position. Motor at bottom position. Best mph and hole shot was with plate ½ up. Boat would hole shot like #2 with plate all the way down up to ½ up. Above that was nothing but ventilation and hitting the rev limiter if I let it. It would also start to ventilate the prop again at high speed and with the bow trimmed down to safe running attitude. Very unhappy with this set up.

#4 Same setup as #3 with 12p prop with cup added by Nettle's Prop in Austin TX. I remounted the engine at the highest mounting holes. A full 8.5” higher than the factory setup with the jack plate all the way up. Best mph and hole shot was with plate ½ up. Boat would jump up quick, but would ventilate as soon as the boat pitched over to get on plane. Motor would shoot to the rev limiter if I let it. Eventually it would hook up and stay hooked up.

#5 Same setup as #4 with Powertech SWC3 11p 3 blade with aggressive “hard wall” cup. Jack plate is all the way up. Boat will jump up great, but again it would ventilate at the pitch roll, but would hold 5000 rpm no matter how much throttle I gave it during the blow out condition. It would hook back up about 2 seconds later. With this setup the boat will run in less than 16" water over a hard sand bottom in flat water conditions and much less if over soft bottom. It will jump up on plane in 20” water. Those are real measured numbers in salt water.

I will admit that I have done too many mods to this boat in the quest to fish shallow. I should have thought more about what I needed when I purchased the boat and purchased something with a tunnel and sponsons. I am done with mods on this boat. In fact, once I finish the re-decking of my Mowdy S10 scooter boat I will be taking the jack plate off this boat and returning to the 12p prop. While very fishable in shallow water, this current combination puts too much stress on the transom for my liking.

 

[richg99]

Nice detailed explanation and the added "results tables" are very clear.

Now that you have the Mowdy, you won't be needing much from the tinny.

I think the guys on here would like to see a picture of your Mowdy. Most of them have never seen a Texas Flats Scooter. I posted a similar picture a month or so ago.

It seems that most areas do not need a true shallow running boat as we do.

I have a new-to-me 2007 1756 ST Lowe that floats shallow enough, but doesn't run as shallow as I'd like. It is not a flat bottom. I am still getting to know the boat, but I doubt that I'll ever go as far as you have in tuning it.

regards,

 

[Stumpalump]

That was a very cool post. We all like shallow and you showed how to do it. We like speed too. Notice the fastest speed is with the lowest height. You got more leverage to carry the bow is why. Last two boats I owned benefited speed wise from a lower height. Best trim beats max height everytime for top end. The best I've seen is when you can get the max trim by being deep and then go up to get that 200 rpm of slip your charts are showing but you have to have the rpm room up top. Of coarse the right prop, weight balance yada yada are all in the equation to max out what you have. My old 16' Valco went from 28 mph to 37 mph just from tweeting all the setup. It was mounted way to high and trimmed way too low to stop ventilating. That boat came to life once I was able to trim it up.

 

[Ebug]

Rich,
Here's a photo of my little scooter boat when I brought it home. It was purchased knowing it would need a deck and transome....even though the owner and the boat shop swore it didn't need it.


I've included a picture of a 40hp Johnson mounted to give size perspective. These boats are 10' long, 5 wide, and will carry 2 people max. I've heard tell of these boats running in 3”-4” water. I doubt that is two 260lb fellas like myself. LOL


The boat is currently stripped down to the raw hull with the deck, transome, stringers, and foam removed. It will go back together much littler than before. The plan is install a 30hp yamaha 2 stroke tiller motor and no console/steering/battery to get the weight down as much as possible.

Stumpalump,
I hear on the tuning for top speed. I knew I would have to sacrifice a bunch of speed to get the motor up, which is ok for my fishing application. I was surprised at the top speed not taking much of a hit between the 12p and 11p prop. I'm guessing that is due to the high efficiency of the application specific PT scooter prop.

Rob

 

[richg99]

Neat.

I looked, online, at a similar boat just before I bought my current 1756 Lowe. What pushed me towards the more "normal" tinny was use on some larger local freshwater lakes. Plus, I am old, and I figured I needed a seat for my fat butt most of the time.

When you get her done, let's go fishing on the coast someplace. I'd love to see how a scooter really runs. We'd have to stay in "deep" water of a foot or more, given my 250 lbs. Ha Ha

Thanks for sharing.