I would like to find out if anyone else has experienced this. Boat is a "95 panteraII 150efi. While cruising at 50-55 on smooth surface going straight,
every so often the boat jumps slightly in the back. The only way I can describe it is like someone kicked the side of the boat in the back. Its not a hard jolt
but it is noticeable. Seems to happen every 30 to 40 seconds. Seems to have a rythem to it. There seems to be no change in rpm or speed. This weekend was the
first i ever noticed it. Any ideas?
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A kick in the back
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 catman2 |
A kick in the back |
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Posts: 14 (05/20/08 06:36) |
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topwater |
Thoughts | ||
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Posts: 308 (05/20/08 07:12) |
More than likely this will keep up till something finally gives out and you find it but my guesses would be something electrical breaking down on the engine like a coil pack or switch box dropping a cyl or two for a second. you might also want to check your prop nut for tightness and the prop hub insert to be sure it not slipping or jerking but these are only guess.. I think it's happening so fast right now that you are not noticing any change in RPM or Speed but it there. |
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Gary Hollander |
I sent you a message... | ||
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Posts: 587 (05/20/08 07:23) |
Check your messages...
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Bass Cat Boats |
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Posts: 11701 (05/20/08 03:31) Registered User |
Either the propeller has lost some bite, or the engine is too low, or too high. Either could cause this based on the propeller.
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oldtimer57 |
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Posts: 895 (05/20/08 03:43) |
Here's what I would bet is happening... As you run up or down a river, you pass over lots of submerged hazards (humps, walls, big rocks, trestles, trees,
etc. When the current is moving, it produces enormous pockets of underwater turbulence that you can see if you look carefully. When you run thru those, they
can interact with the gearcase/skeg/prop and even the boat bottom to produce that "disturbing motion" you are describing. You won't see this on
a true lake, or on a reservoir where the current is not flowing. But with all the water of late, most rivers are moving right along and this is a common
issue... More noticable the faster the current flows and the shallower the water. You probably will never see this in 300' of water, but in 10-20',
it is noticable.
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basscat brett |
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Posts: 22 (05/20/08 07:36) |
I'd check to make sure that your engine to jackplate and jackplate to boat bolts are good and tight while you are checking things.
I had a similar experience when I first bought my boat (used). At or aorund 60mph the rear of the boat would step out hard sometimes and I never could figure out why - I figured my setup was no good. One day while messing around the back of the boat I checked the bolts that held the hyd jackplate to the boat and they were very, very loose. Since I tightened everything up the "step out" has never re-appeared. I am only guessing they were related but it's worth a check. |
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catman2 |
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Posts: 15 (05/21/08 06:27) |
I'll check all the bolts and steering play this week and see if I can find anything. Could motor being to low cause it? Currently setting 3.5''
below pad running a 23p trophy with some right hand torque.
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Bass Cat Boats |
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Posts: 11705 (05/21/08 08:34) Registered User |
OT57,
Nope, we know what he has, he has a development on an air pocket on the propeller from the engine height porbably being lower. The Pantera Hull is the most common to encounter this, though all can on this style of hull. It is probably not current etties and is more likely the engine height. BCB |
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Gary Hollander |
Spoke to CatMan2 | ||
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Posts: 588 (05/21/08 10:57) |
Years ago, the "boss" walked me thru correcting this on a PII, which was experiencing the same situation. Engine height is key, along with the
tightness of steering components and jackplate to transom and engine to transom.
Generally speaking, CatMan was getting right-hand wheel torque, and when in "chop" his hull is hooking up good, and when in "calm" he's getting the "kick". I believe from talking to him, his engine is too low, but will reserve judgement until he tales his measurements. He doesn't have hydraulic steering, either. After he takes some measurements, and checks his stuff out, I'm pretty sure he will have it solved. I have dealt with this "kick" on several past rigs, and again, it comes back to proper set-up... Gary Hollander |
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oldtimer57 |
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Posts: 896 (05/21/08 11:50) |
You guys certainly know your boats better than anyone. I've never seen that particular problem, but that doesn't mean much. I have seen the water
turbulence cause a hull to seem like it is "hunting for something" as it runs down the river. On Lay, where I fish, this is common after big rains
upriver that have the river stained and trash-filled. Never ridden in a PII, so no experience there. But a family member's R-type boat, and another's
J-type boat exhibits this problem on fast-moving water regularly...
I had suspected that was the problem based on the water flow rate at local rivers here as we have had a _ton_ of rain this spring as compared to last year... I've not seen it at places like Guntersville, but on the Coosa it is very common to get this "twitching" feeling when up on plane.. |
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Bass Cat Boats |
Your GooD OT57 | ||
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Posts: 11712 (05/22/08 10:27) Registered User |
OT57, you are very knowledgeable and way above average in most of your pointers. There are a few things that
step up and we occasionally are able to even teach you, this is one. Your knowledge is great, and you have a capability to have a wide range of intellect into
more than boats. We are very aware of our product, and most others. Just realize that your knowledge of boats is huge, though it is a little like your
knowledge of cars, AJ Foyt, Petty and Andretti could still teach you a thing or two. And our knowledge, while not on the same level of technical expertise as
AJ's, is on a level to where we see hundreds of different scenarios and have played with many things you would not imagine. We work very hard to know more
about out product and the products we use than any other company. It is a passion, as well as a hobby and our careers.
That being said, we are very glad to have you on this board and stopping in to visit. When the board went closed to registered users only, we wondered whether that took you out of the involvement. You bring plenty to this board and we appreciate your involvement. Little things like Ceramic brake pads and nice things for folks to consider that you have in your pea brain! Thank You! BCB PS: Now, if we could just get you out of that little pocket PC your drivin'. |
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oldtimer57 |
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Posts: 898 (05/23/08 08:47) |
BCB:
Just a note. I have seen my share of odd hull things. friend had a customized race boat several years back and it was about the most miserable hull I have ever worked with. About the best word to describe it was "unstable". It was highly sensitive to trim, motor height, prop style and so forth. I remember talking to an airplane designer years ago at an air show. I won't mention his name, but his initials are B.R.  In any case, he had built
this incredible airplane (experimental) and had flown it until he knew every characteristic at every air speed, angle of attack, etc. Then his ground crew
decided to spiff it up for the bit air show and added some pin stripes. This was an early work with laminar flow wings, and when he took it off, at about 30
feet it did a perfect snap-roll. But without full up elevator, and full right rudder. On its own. Once he changed underwear and started studying the issue,
he removed the pin striping and the problem went away.
That was an apt description of this particular hull I was mentioning. Any little change resulted in a big handling change. So I have seen it, but not in a bass boat. Obviously I have not driven every hull around. Were I Bill Gates I might even own every hull around, but I'm not and I don't. So your
hull characteristic sounds perfectly reasonable, although it would be an interesting discussion as to how you actually discovered this. It is not exactly
easy to produce high-speed photographs to see what is going on, although I have seen a couple showing how a gearcase blows out at high speed, so it is doable.
And no, I'm not asking you to reveal any secrets you might have, more of an "attaboy" for figuring it out in the first place. I could see myself
spending months on that before developing a clue as to how/why, although I would certainly have been tweaking trim and height to see what the effect would
be...
But you went further which was what got my attention. Most would have just said "raise your motor, we found this makes the problem go away..." But you guys identified the problem as well as a solution, which caught my eye. I always prefer that kind of ending to any story, as it is nice to know what causes something as well as how to fix it. Obviously that saves a lot of money in outboards, as if you burn a piston and don't fix the cause, you will be back at the parts place soon enough.
In any case, impressive research to discover that. That is something I would expect to have come from some of my friends out at JPL or at NASA.
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