Help with RT188 on Performance and Prop and Engine Height

[bunz559]

There's tons of information, but it seems that many rigs vary. I'd like to get some insight on increasing the performance of my 2014 RT188, or confirmation that I am running either optimally or not and how I can improve that. Although it's a 2014, my rig has a 2017 or 18 hull so there are trim tabs (replaced through Ranger from previous owner). Current setup is the following:

115 Pro XS 2 stroke
no jack plate or setbacks
Mounted on 2nd hole down
19 pitch Michigan Apollo
Currently running 45mph at full throttle
5600rpm at full throttle
(These numbers were taken just this past weekend with 400lb of people and maybe 50lb of gear. Glass calm water with no wind.)

I believe with the current rig, using online calculators, I am getting roughly 7.55% or 8% prop slip. Is this considered good, ok, or bad?

I've read many threads where people are running larger pitch props, 20's and 21's, and getting better/faster performance than I am. Curious as to why and how they're running such large props without bogging down the engine so much. Could I benefit from increasing my prop pitch at the same time lifting my engine to the 3rd hole? My hole shot is decent and boat gets on plane nicely, but if there's any room for improvement whether it be hole shot or a few MPH, I'd like to try. I recently just installed the Apollo prop from the stock 19 pitch aluminum and it made a worlds difference with the hole shot and gained a good consistent 1.5-2mph at full throttle.

Thanks in advance!

[Bill Reynolds]

I replied to your other thread with specifics but I have exactly the same boat running a 20 pitch Laser II with essentially the same results as you.

[Sim32]

The Merc Lazer II has proven to be the best performer with the 2 stroke I believe, though your numbers seem similar with the Apollo, and based on your numbers it sounds like it’s dialed in pretty close.
I have both a 19 and a 20 pitch Lazer II, just me in the boat it’s a little faster with the 20, with more load the 19 is best so I just run the 19 all the time. Max rpm on our motors is 5750, the closer you get to max, the more power it puts out, 2 strokes like to rev. I can hit that with the 19p (vessel view mobile, so I’m getting an accurate reading) and have never had the rev limiter warning horn sound. Truth is, the 188’s are not 50+ mph boats, some guys have achieved that but for most these things run 47-48 with very little bow lift. I’ve hit 49 but am really not interested in doing a lot of screwing around to try and squeeze a little more out of it. With 2 people and regular load I run 45-46 or so and I’m fine with that. Weight...and we’re it’s located does change things with the 188.
I changed to lithium batteries so lost about 150lbs from the bilge area, surprisingly it didn’t change top speed, but it absolutely rockets out of the hole and the overall ride improved as well. There is a Facebook group for Ranger Aluminum owners and there’s advice given mixed up with 2s, 4s, 188, 198P, it’s kind of nuts really. And quite a bit of recommending grinding off trim tabs...no thank you.
My trade in on the 188 was an 18ft Ranger Cherokee that was like a carnival ride when trimmed up, I’ve no interest in going back to that, I’ll gladly keep my 47mph, flat riding, non bouncy trim tabbed boat.

[Bassakwards]

I've got a 2016 with the regular Merc 115 4s, I run a 21p Solas SS prop that the dealer put on. In the winter, alone with 1/2 tank of gas I can hit 47mph. Normally, I am full of gas with a passenger and a ton of tackle, I still get 45mph. I don't run it, wide open often though, it cruises just fine at 40mph.

[tcesni]

Seems like you should be able to get a bit more. With a similar load I get 42 mph with a 90 Optimax and you have about 33% more horsepower. I have my motor mounted one hole higher than you do and have some cup added to my prop.

[Panama]

I now have four props for the RT. When I bought the boat about 6 years ago, nobody knew much about what prop to run. My dealer let me trade and try different props. I think I tried 8 different ones. The Laser II 20P ran the best. That is the one I run the most. I dinged it in Florida a couple of years ago and had it reworked and had a little cup added. It ran better before it was reworked. It ran better brand new right out of the box. I have a Yamaha SS prop I picked up cheap, a spare aluminum 19 prop I got for free, the Laser II and one a prop guy made for me. The Laser II 20 is the best prop.

You are running pretty good as is. Whatever you might achieve would be minimal and would change a lot with waves, wind, weight distribution, type of fuel, amount of fuel and air temperature, among other things. You could work a lot and get a MPH or maybe two and lose it 2 weeks later because of something that changes. The hulls are handmade and hand welded and can be a little different one to another. They fish great but are not fast hulls. When you get around 45 or so with gas and gear, your money is best spent on new fishing gear and your time is best spent using it. IMHO.

[bunz559]

When you get around 45 or so with gas and gear, your money is best spent on new fishing gear and your time is best spent using it. IMHO.

I like that. Thanks for the insight.

[GeauxTide]

When you get around 45 or so with gas and gear, your money is best spent on new fishing gear and your time is best spent using it. IMHO.

Panama got it right. As indicated below, I run a 19" X7 in the summer and a 20" Laser II in the winter. I'm running exactly as you are - I was getting 46-47 until I put in the port console, now 45. The X7 holds the boat like it's on rails and I'm completely satisfied. If you want more performance, forget the JP route - 2mph and a lot of wasted time and gas. Get an Xpress if you want performance.

[bunz559]

Thanks everyone for the input. Thread after thread I've read. I think I am going to just be happy with it for now. Considering (day dreaming) trying to find a used 519 or 919 with a 200 or 225. That'll most definitely solve the speed issue. Before then, I have to figure out a tow vehicle and garage/house large enough to store a bigger boat. Very very expensive planning.

[n2ratfishin]

If you're after "speed" I'd suggest looking at the brands known for that feature. My old Sabre FTD with a 175 ProXS fit in a short garage, Seems like you'll need about 21 feet of depth? That boat was all over 70 MPH with a regular tournament load and the live wells empty. If you can fit a 519 you can for sure fit the Sabre FTD. Cat's PII will fit in about 22' depth and is screamer compared to others with a 200. I've driven them well into the 70's...a solid 75MPH boat with a 200. Outside of that you'll be looking for a Bullet, Allison, Stroker along with a few others. I've drove a Z519 with max HP and was doing well to get into the 70's. Mostly they are a solid high 60's boat.

I've managed 50 a couple of times with my 2017 RT188 ProXs 4S and I don't have a jack plate. I run the 20 Laser II that came on the boat from Ranger. At WOT it'll be turning about 5900 RPM's. That is not bogging down the engine. It's pretty much a 47 MPH boat. A kid could drive it. I cannot say that for my old boats that were set up too run. You have to drive those boats to get the full potential. A mistake at 70 MPH in an 18' boat can lead to bow hooks and injury.

IMO you just don't buy a 115 powered boat in hopes of speed. Nor could the faster boats I've owned or driven come close to the economy of my RT188. I can fish for two or three days on 10 gallons of fuel, that's lakes like KY or Guntersville where you are going to run. Sounds like you are set up about right, I'd just fish and enjoy.