Help with my top end speed

[AnglerMike]

Hello fellow anglers. I've got a 2009 Skeeter SX180 with a Yamaha F115 4 stroke. I've installed a manual 4" JP and with a full load with two guys were only running about 43-44mph. I have not fine tuned the JP at all yet but my question is can I get this rig running 50-55mph? I believe my rpms are around 5000.....what can I do? I love this little boat.

[greg88]

Research the max rpm for that motor then tune to get it running close to that rpm in the summer temps let's say it should turn 6000 rpm at this point you would drop prop pitch or raise motor *(need to watch water pressure )* good luck a 6 to 10 mph increase is a lot but possible

[AnglerMike]

Thanks man. I'm looking forward to getting everything I can out of this thing.

[Fatshaft Merc]

You probably won't get there with the 115. That boat is underpowered, it needs a 150 to get into the mid 50's.

[JR19]

First and foremost you have to have a good healthy motor with good plugs, fuel and all mechanical stuff adjusted properly. I know mentioning having everything in good working order may sound like captain obvious but the reason I say this is because I knew a guy who spend a ton of $ chasing speed only to find out he had worn out spark plugs and this throttle linkage was not going open 100%...had he had the health of the motor checked out before buying props and adjusting the jackplate he would have saved a lot of time and $.

I would make 50 my goal because I don't see it doing 55 on a GPS...before doing anything there is some critical information you need to know. Suggested max rpm for motor. Suggested minimum water pressure at wide open throttle. Before playing with props or motor height you must know the two things I mentioned. I am not familiar with your particular hull so I can only make a guess at what prop to pad to start with. What is your current prop to pad? Without knowing I will suggest a starting point of 3.5". Raise the motor .25" at at time until the rpms increase and the speed decreases OR the water pressure gets to low. There will be a point when you get too high and the motor is gaining rpm from slipping because its too high. This is when your rpms go up but the speed goes down. Also too high will have a sudden drop in water pressure. I know moving the motor up/down .25" does not sound like much but once you get close to the sweet spot .25" can make a big difference. Patience is key if you have a manual jackplate because it takes time to adjust and run. Alos you never mentioned your current prop. I would think a stainless steel 3 blade 22 pitch is what most boats in the 18 ft range with 115 horsepower are running. "Typically" a good (with good being the key word) a good prop guy can find you 1-2 more mph buy working your prop. Larger HP motors may see 1-3 mph gain but a 115 is going to be more close to a 1 mph gain. I would use Mark Croxton to find the last bit of speed in my prop.

Here is a link to mark

http://www.marksprops.com/


Here is a easy way to learn how to measure prop to pad if you are not familiar with how to check.

[BOATS]

My F115 Pushes me 48 with an aluminum 21p prop, although I am running an Xpress H18 without a plate. And my max rpms are 6000

[grout-scout]

You probably won't get there with the 115. That boat is underpowered, it needs a 150 to get into the mid 50's.

Yep.

You’re just wasting time & money on anything you do.

[RFSims]

Yep.

You’re just wasting time & money on anything you do.

Agree. 47 (GPS)is probably the best you could do and I have doubts about that and that is with only one person in the boat.

[RangerRic]

What JR19 said.

I have an R70 with a Merc Pro XS 115 four stroke and I hit 51.6 gps
with aluminum prop sans jackplate. Your boat is 200# more than mine and
you do not have the SHO, but, I would still think 50 is attainable.

[billnorman1]

First and foremost you have to have a good healthy motor with good plugs, fuel and all mechanical stuff adjusted properly. I know mentioning having everything in good working order may sound like captain obvious but the reason I say this is because I knew a guy who spend a ton of $ chasing speed only to find out he had worn out spark plugs and this throttle linkage was not going open 100%...had he had the health of the motor checked out before buying props and adjusting the jackplate he would have saved a lot of time and $.

I would make 50 my goal because I don't see it doing 55 on a GPS...before doing anything there is some critical information you need to know. Suggested max rpm for motor. Suggested minimum water pressure at wide open throttle. Before playing with props or motor height you must know the two things I mentioned. I am not familiar with your particular hull so I can only make a guess at what prop to pad to start with. What is your current prop to pad? Without knowing I will suggest a starting point of 3.5". Raise the motor .25" at at time until the rpms increase and the speed decreases OR the water pressure gets to low. There will be a point when you get too high and the motor is gaining rpm from slipping because its too high. This is when your rpms go up but the speed goes down. Also too high will have a sudden drop in water pressure. I know moving the motor up/down .25" does not sound like much but once you get close to the sweet spot .25" can make a big difference. Patience is key if you have a manual jackplate because it takes time to adjust and run. Alos you never mentioned your current prop. I would think a stainless steel 3 blade 22 pitch is what most boats in the 18 ft range with 115 horsepower are running. "Typically" a good (with good being the key word) a good prop guy can find you 1-2 more mph buy working your prop. Larger HP motors may see 1-3 mph gain but a 115 is going to be more close to a 1 mph gain. I would use Mark Croxton to find the last bit of speed in my prop.

Here is a link to mark

http://www.marksprops.com/


Here is a easy way to learn how to measure prop to pad if you are not familiar with how to check.

This is a good rule of thumb, but on my boat which very few others have, I run a 16 inch diameter prop which needs to be a little lower because it cavitates if not run lower.

[Al from Canada]

Hello fellow anglers. I've got a 2009 Skeeter SX180 with a Yamaha F115 4 stroke. I've installed a manual 4" JP and with a full load with two guys were only running about 43-44mph. I have not fine tuned the JP at all yet but my question is can I get this rig running 50-55mph? I believe my rpms are around 5000.....what can I do? I love this little boat.

How heavy are the two guys?

[billnorman1]

How heavy are the two guys?

I find this amusing although essential.

[Trickyrick]

That is a heavy boat for that engine and 2 guys. I have no doubt you can do better than 44 but I used to have a little Skeeter SS140 with a 115 on it and alone in perfect conditions and running light I think my fastest was around 56 or 57. That SX180 has to be 400# heavier and adding a second person.... With 2 adults in that 140 and tournament load think 50-51 was about it...

Best you can do is drop Pitch raise the JP and see if you can get the RPMs up. Physics are not with you though. Watch your water pressure.

[Teadow1972]

Simple answer is no. You wont attain mid 50's with that set up. You can jackplate it, raise it, lower it, re prop it, strip it down bare bones. If you can get a steady 45 loaded and fueled up your doing fine.

[cubswin]

I had a 18 (17'7") javelin with a 115, and it loaded light would hit 55 with the right prop. With two people it was more like 47-50. Suspect that boat was lighter than your skeeter, and the javelin hulls were fast hulls. I think you might get to 50 loaded light, but 55 is a stretch. Unless you are judging speed on the speedo.

[ECobb91]

I’d think 50 might be doable but anything more is wishful thinking. My 17’ nx750 with a 115hp runs 48-50mph alone and 46-48 with two people loaded