bought an rt188 about 45 days ago with a Yamaha 115. Prop was aluminum 16 pitch. Top speed my 210 lbs my 240lbs cousin and full tank was 37 mph on the gps. Reading on here people are getting up to 50 mph with a 21pitch SS. I bought a 19 pitch SS thinking I would get to somewhere in the 44-46 mph range with a good hole shot but only got 39-40 with just me and fuel. Is there something else I should look for/add. Ps. This is not my first boat.
What hole is the motor mounted in? It might be to low. What Rpms are you turning?
BassCat Cougar FTD w/Suzuki 250SS
I have a 19p stainless Spitfire X7 on a Merc 115 4S and I consistently run 46-47 with two guys, half a tank of gas, full livewell, and a tourney load of gear.
2023 Ranger RT188P
2023 Mercury Pro XS 115
Garmin 126SV (2), 93SV, LVS34
Minn Kota Ultrex
I'll have to check mount position tomorrow. Running about 5900-6000 rpms.
You're way over propped. Most of us have Mercs with a 19" X7 or a 20" Laser II, running in hole #2. I have a SOLAS 21" that hits 48, but steering torque is terrible. Several are running 4" setback or Micro Jacker. I'm running 46@5500 right now, but it takes about 40 hours for the Mercs to settle in. Your motor runs to 6300 with 2.15 gears, so I suspect that the motor is flat on the transom.
2015 Ranger RT188 DC; BassCat Storage Box; Mercury Optimax 115ProXS;
19" Spitfire X7; Vessel View Mobile; Minn Kota Ultrex 80; GForce Handle;
TM Eliminator; Helix 7 G2N SI Combo F/R; HydroWave KVD; BBT 4" Angled Bow Mount; Durasafe Locks for Electronics and Ultrex;
Twist Step Boarding Ladder; EZEE Step ES1; BAC RAC Rod Storage; Motor Mate Transom Saver
Just to confirm, are your speeds from a GPS?
2018 Ranger RT188 SC Black/115 hp Yamaha SHO 4-stroke; Garmin LVS34 - north
2018 Ranger RT188 DC Black/115 hp Merc Pro XS 4-stroke; Garmin LVS34 - south
14' Mirrorcraft tin boat (ancient) with a 9.9 Mercury 4-stroke, no electronics; catches fish anyway
Something just does not sound right here. 6000 RPM with a 2.15 gear ratio, 19 pitch prop, and figuring a generous prop slip of 10% you should be hitting 45 MPH. To get that down to 39-40 MPH you would have a 21% prop slip.
To catch everyone up (including me). No set back or jack plate, flush mount. Yes mph is using lowrance gps. And yes, Skeeterbait, something appears to be amiss. Motor has +/- 25 hr on it and I broke it in by the book. Going now to check mounting position. With the 16 pitch aluminum prop rpms were @6100 fwiw. Really appreciate all the help fellas. Love the boat but I do seem to be missing about 15% of my speed.
Motor mount has 4 holes. Mounted second from top. So next to lowest possible mount.
o
x
o
o
have some great pics but don't know how to reduce file size. I'll keep trying.
What is the idle rpm according to your tach? Wondering whether your tach is off. Are you stopping the motor from going over 61k with the throttle or is that with it flat out?
Tim,
fishing Thursday morning so I'll check the idle rpms. 6100 was wot with the aluminum prop. 5950 wot 19 pitch SS prop.
Huh. Something wrong there alright. You are trimming the boat up?
The paddle handle is mounted to the bottom of the boat.
I trim till I hear cavitation. Have tried less trim just go slower.
I wonder if your tach is off and the motor's not firing one cylinder. Can't see how you'd get the combination of speed, rpm and propeller otherwise. Might be a trip back to the dealer.
I have a 21p on my 115, I hit 48mph gps. Mind you it's an Xpress but still.....
XPRESS H 18 SS, YAMAHA 115
Did you buy the boat new? What year is it and also year of motor? They changed the 115 a couple of years ago and gave it a little more power and rated the RPMs higher. I ask about the boat and props being new because an aluminum prop can lose a lot with just a small hit on a stump or something. You don't mention the brand of the props you ran or if you bought it used or new???Originally Posted by Littlefred
It seems some brands of props are better than others. The 19 pitch is probably not enough prop or the right design of prop. If I had the setup you have I would buy a Laser II 20P prop for it. I think both Yamaha and Merc made good props and I am sure there are others. I have run both of those and some other brands and the Laser II did the best for me. Different brands or models of props can make a big difference even in the same pitch. Also weight and weight distribution makes a huge difference on these boats. I would try to see if you are carrying a lot of junk you don't really need and get all the weight you can to the rear. Just my $.02.
Something is not right.
----------------------------
The bitterness of poor quality is remembered
long after the sweetness of low price is forgotten - Benjamin Franklin
2013 RANGER RT188 - YAMAHA F115 - ULTREX - LOWRANCE GRAPHS
LOCK-N-HAUL Transom Saver, ALL ABOARD Emergency Ladder
1996 RANGER CHEROKEE - 40 YAMAHA
Boat is a 2015 new old stock. The dealership in Smithfield NC had several in sold units from 2015. Not positive about motor yr model. Both props were new. Pic is stamp on new prop.
Loading: My tackle box is comparatively light so just me, fuel, and live well water.
Serial number on the engine will tell the year
Reply With Quote