skeeter boat hopping at high speed

[goffball56]

I have a sf175 Skeeter bass boat with a Mercury xr4 150. boat runs great up to 3/4 throttle and starts whale hopping real bad. had a 12in jack plate and went with no jackplate and back to a 6in still the same thing. Also tried lowering and raising the motor and no change. the motor has a 24p ballistic XL prop. tried a tempest plus 23p no change. left side fin on lowerunit is boken would this have an affect on this? Any suggestions would be great. Thanks

 

[444]

Re: skeeter boat hopping at high speed

Triming the motor up and down a lot make any difference? I've heard some guys saying trim tabs can help with this issue.

 

[Texasmark]

Re: skeeter boat hopping at high speed

I have a sf175 Skeeter bass boat with a Mercury xr4 150. boat runs great up to 3/4 throttle and starts whale hopping real bad. had a 12in jack plate and went with no jackplate and back to a 6in still the same thing. Also tried lowering and raising the motor and no change. the motor has a 24p ballistic XL prop. tried a tempest plus 23p no change. left side fin on lowerunit is boken would this have an affect on this? Any suggestions would be great. Thanks

I run the same prop and no problem. If you are talking about the AV plate being broken, when you are blasting away, it is out of the water pretty much.

Whale hopping is called porposing. It is caused by the speed too low for the trim position. Tuck in the trim and the bow will come down and more of the boat will get wet and it will smooth out, or just stay on it till you get going fast enough to level out, or tuck it in, hammer down on the throttle, and then slowly trim it out watching your rpms and mph increase.
Mark

 

[jbcurt00]

Re: skeeter boat hopping at high speed

I have a sf175 Skeeter bass boat with a Mercury xr4 150. boat runs great up to 3/4 throttle and starts whale hopping real bad. had a 12in jack plate and went with no jackplate and back to a 6in still the same thing. Also tried lowering and raising the motor and no change. the motor has a 24p ballistic XL prop. tried a tempest plus 23p no change. left side fin on lowerunit is boken would this have an affect on this? Any suggestions would be great. Thanks

Are referring to what is commonly called Porpoising? I'd guess the broken fin could certainly cause some porpoising, depending on how damaged it is. Post a pix of the motor on the jack plate you last ran it on, and some pix showing the plate's settings/adjustments (if equipped), the plate to the transom, and the motor to the plate. More knowledgeable iboaters will get you squared away, but they'll need pix for reference...

Here are 2 links to info @ porpoising:

Iboats

Another site

There is lots of info @the iboats forums, take a look around you may find answers to questions you didn't know needed to be asked.

I hope those 2 links help answer your question & the iboats crew will get ya planed out & riding smooth again soon..

Triming the motor up and down a lot make any difference? I've heard some guys saying trim tabs can help with this issue.

I think you meant trimming the motor in & out, adjusting the angle of the motor relative to the plane of the water and the plane of the transom. Tilt, if equipped, would be more likely to be described as adjusted up & down, but is usually only 2 stops/settings: tilted up for trailering & tilted down for running, so not ideal for adjusting the motor to reduce porpoising.

Trim tabs and the additional hydro fin are both 2 ways of reducing porpoising. But if the hull has a hook, the fore & aft weight distribution, the motor's trim angle or motor height on the transom are the problem, you might address those areas 1st. Then if all else fails to correct the porpoising, try the tabs or the fin.

 

[Scott Danforth]

Re: skeeter boat hopping at high speed

your jackplate is used to adjust the engine height (for load, water depth, etc.), your trim is used to adjust drive angle. the links will help. Just raising and lowering the motor alone wont solve porpoising.

 

[CharlieB]

Re: skeeter boat hopping at high speed

Surprisingly, your trailer can contribute to the problem. If the trailer does not support the hull correctly, over time the 'pad' can 'warp', out of 'flat' and develop either a slight inward or outward 'bow' which negatively effects high speed.

Get under the boat with a yardstick and look at the pad, check to see if it is flat fore to aft.

 

[goffball56]

Re: skeeter boat hopping at high speed

i meant by raising and lowering the motor we did so by moving the motor up and down on the jackplate. you know when your running almost wot and trim up the motor will quit trimming at a certain spot and thats when it does it the worst but that where your suppost to get the best speed. had it out in rough water and a couple of times full throttle and trim out it would lift the nose and run great then all at once the it would let go and fall on its face and start porposing? it starts when running about 50 to 55 mph. i wouldn't think i should have to run with motor trimmed down to make it quit cause then its just holding back alot. it also seems to quit when i turn to the right but get worse when i turn to the left???

 

[Scott Danforth]

Re: skeeter boat hopping at high speed

when running with the jack plate, position the motor so the Anti-Cavitation plate is about 1-2" above the bottom of your hull. Higher than that is for really shallow water fishing. then use the trim to control the porpoising from there.

 

[goffball56]

Re: skeeter boat hopping at high speed

tried that already and still the same thing. the left side of the anti cavatation plate is broken in two places which pretty much most of it is gone, would this have an affect on it?

 

[goffball56]

Re: skeeter boat hopping at high speed

Would installing smart tabs fix this problem?

 

[Faztbullet]

Re: skeeter boat hopping at high speed

What year SF175?? You could have a "hook" in hull or weaked stringers causing bottom to flex also. I have also seen this on the early Hydro-sports DV series with the Xr small gearcases as there is not enough prop to lift and hold boat on pad.

 

[goffball56]

Re: skeeter boat hopping at high speed

it is a 1990 sf 175 sx with a xr4 150 with big gear case.

 

[Scott Danforth]

Re: skeeter boat hopping at high speed

tried that already and still the same thing. the left side of the anti cavatation plate is broken in two places which pretty much most of it is gone, would this have an affect on it?

that will not help the situation. have you looked into getting it repaired.

 

[CharlieB]

Re: skeeter boat hopping at high speed

i meant by raising and lowering the motor we did so by moving the motor up and down on the jackplate. you know when your running almost wot and trim up the motor will quit trimming at a certain spot and thats when it does it the worst but that where your suppost to get the best speed. .............

Peak trim is NOT necessarily where YOUR boat will be most efficient. You need to trim up SLOWLY, just a 'touch' at a time until you get to that 'sweet spot' for YOUR BOAT.

Prop rotation causes a difference in handling turning left or right, if you had a reverse rotation motor/prop, you would notice the opposite effects than what you have now. A lot of this is also caused by improper mounting height and trim angles.

 

[goffball56]

Re: skeeter boat hopping at high speed

that will not help the situation. have you looked into getting it repaired.

I have another lower unit i plan on replacing it with.

 

[goffball56]

Re: skeeter boat hopping at high speed

Peak trim is NOT necessarily where YOUR boat will be most efficient. You need to trim up SLOWLY, just a 'touch' at a time until you get to that 'sweet spot' for YOUR BOAT.

Prop rotation causes a difference in handling turning left or right, if you had a reverse rotation motor/prop, you would notice the opposite effects than what you have now. A lot of this is also caused by improper mounting height and trim angles.

it seems the sweet spot is just when my boat starts porposing. as i said previously i have already tried raising and lowering jack plate and has no affect on the porposing. i understand what your saying about the prop rotation with the handling. i figured this would be an easy fix and have never experience a boat acting like that at high speeds.