H18 and VF115LA performance project

[Xpress4Sho]

Here is yet another "what should I try first" post

I’ve sent this to propsgod.com cause I've heard good things about them and will probably order through them. But thought I would float this out to some other xpress owners as well.

Xpress H18
115 Yamaha VMAX Sho
6” jackplate with engine set at 3.5” pad to prop (seems pretty standard)

Currently at WOT RPM is at 6000-6100 RPM and trimmed about 50%
GPS 45 MPH
Current prop is a PowerTech 19” (sorta their base line Stainless prop).
Hole shot is great

Issue:

· I can’t trim it out past 50% on WOT because it will quickly start to blow out/slip/cav... (Whatever you want to call it)
· When at 6000/6100 RPM and running top speed of 45 it seems as if it can feel the prop struggling to maintain grip (like you can feel little prop slips here and there)
· 45 mph seems low for this boat, others seem to be running low 50's easy

Goal is simple:

Run WOT in the 5800 -6100 range
Reduce blowout at higher trim
maintain decent hole shot
Be up in the 50mph range
Not mess with engine height much more, until I'm confident in the prop

A general thought:

I’m thinking it might could turn the 21” in the 5800 range since its already running in the 6100 range with a 19"
per this the RPM range is 5300-6300 http://www.onthewater.com/wp-content...heet_VF115.pdf

Options I've considered:

Looking at another 3 blade and bumping up to 21" (I've heard some of these performance blades are made for higher engine heights)
Laser II
Turbo 1
YAMAHA Pro series

OR

4 Blade for more overall lift and grip and bumping it up to 21”
Trophy Plus
YAMAHA Performance 4


So.... What should I try first?

[BOATS]

Without jackplte and having an aluminum prop I roll around 46 - 47 and on good days have hit 48 gps.

[willymac]

When I had my h18 with f115, 6" plate and yamaha pro 21, I would easily hit 48-50 with two people and could stretch it to 52-53 by myself, all gps readings. My boat liked a lot of trim, probably closer to 75%. Get a yamaha pro 21 and then start playing with motor height.

[Xpress4Sho]

When I had my h18 with f115, 6" plate and yamaha pro 21, I would easily hit 48-50 with two people and could stretch it to 52-53 by myself, all gps readings. My boat liked a lot of trim, probably closer to 75%. Get a yamaha pro 21 and then start playing with motor height.

Very helpful, thanks!! Just ordered the pro 21, I'll post results once I've run it.

[Xpress4Sho]

Purchased a Yamaha pro series 21p and ran it yesterday, here are the results

WOT 70% trim 5900 RPM 49-50mph (GPS) water pressure 19psi
full tank of gas, fishing gear, 1 adult and small child
Seems to handle a lot smoother at top end
hole shot not as good, but can live with it.

No issues with cavitation, though I did notice some when about half throttle and 44% trim

might go back out by myself, half tank, and trim it up 75-80% (or point of blow out) at WOT just to see if I can get rpm up to 6200 and speed to 52-53

motor is at 3.5 pad to prop, I seem to have plenty RPM, what would raising it 1/2 inch or lowering 1/2 inch do to performance?

[willymac]

Purchased a Yamaha pro series 21p and ran it yesterday, here are the results

WOT 70% trim 5900 RPM 49-50mph (GPS) water pressure 19psi
full tank of gas, fishing gear, 1 adult and small child
Seems to handle a lot smoother at top end
hole shot not as good, but can live with it.

No issues with cavitation, though I did notice some when about half throttle and 44% trim

might go back out by myself, half tank, and trim it up 75-80% (or point of blow out) at WOT just to see if I can get rpm up to 6200 and speed to 52-53

motor is at 3.5 pad to prop, I seem to have plenty RPM, what would raising it 1/2 inch or lowering 1/2 inch do to performance?

Sounds like you have it pretty close to what you are going to get. Start moving the motor 1/4" at a time now, sometimes when you are close it doesn't take much adjustment at all. Next would be weight distribution in the boat to squeeze out the last little bit.

[fuelleak]

I have a 2014 H18, Yamaha F115, 12" Rapid Jack, single PP Blade and see 50 most days. With a partner and his gear, 46-47mph. Zero handling issues. Great boat. Will be hitting the market place here shortly.

[Nickl]

I have a 2014 H18, Yamaha F115, 12" Rapid Jack, single PP Blade and see 50 most days. With a partner and his gear, 46-47mph. Zero handling issues. Great boat. Will be hitting the market place here shortly.

Go down to 3 7/8 it will help you use the rest of your trim .Get more lift these boats have a lot of drag 1/8 can make a lot of deffrents.I had to do that on my x19

[T4Rhin0]

What is the part number on that 21” Pro Series prop? I’m having one hell of a time finding one available right now. My boat runs exactly as the first post states.

[Bcpiper1980]

Have had luck with a Turbo 4 blade in the 20....
52 mph fairly consistently and handles good in turns.