Bass boat porpoising. Wrong set-up?

[rla0248]

1999 ZX195 Skeeter Bass Boat - 19.5 ft.<br />1982 150hp Black Max<br />12" manual set-back/jackplate<br />23p 3 blade SS quicksilver prop<br />Hydro-foil mounted - forgot brand name.<br />Motor appears to be mounted fairly high<br /><br />I recently bought this boat. First I think 23 pitch may be too much, but I'm not sure. Trimmed all the way in, the boat does not get on plane as quick as it should.<br /><br />Once on plane, still trimed in, the bow is plowing down, as would be expected. Trim up a tiny bit and it gains about 500 rpm and about 5 mph. Trim up a tiny bit more and get propoising. Can not run the boat with any bow lift because of the porpoising. Either bow down and plowing or trim up a little and get porpoising.<br /><br />WOT rpm is 4500 - 4600, but that is with the bow down, creating quite a bit of resistance. Speed is probably 40 - 45, but that is just my guess. Dash speedo shows 35.<br /><br />The prop appears to be the standard issue 1982 SS 3 blade quicksilver. I'll get the part number off it and post it tomorrow.<br /><br />Any ideas? Would a different prop help? If so, sugestions please.<br /><br />Thanks

 

[LubeDude]

Re: Bass boat porpoising. Wrong set-up?

Well, I think Im getting what you mean, but lets see.<br /><br />If you are WOT, (wide open throttle), then you should be able to trim out quite abit. If you are trying to trim out much at all at just a cruising speed, you are going to have porposing issues. You can only trim large amounts at WOT!

 

[KCLOST]

Re: Bass boat porpoising. Wrong set-up?

Yea,<br /><br />You need to push over the mess and see what happens at full throttle and trimmed out..<br /><br />Do it carefully, and report back... You should reach 5500 rpms with that motor at wot. I wonder if your engine is working properly? Sure it is running on all cylinders?<br /><br />That prop is not the best in regards to lift however.. There are better ones out there...<br /><br />But test...

 

[KCLOST]

Re: Bass boat porpoising. Wrong set-up?

Oh, <br /><br />And what is the maximum HP rated for that boat...<br /><br />I've been in a lot of Skeeters before and I do recall that they do have a tendency to porpoise more that others... Just curious?<br /><br />Don't want to start a fight?

 

[rla0248]

Re: Bass boat porpoising. Wrong set-up?

Hi,<br /><br />Thanks for the replies.<br /><br />The porpoising seems to occur at any throttle position after planing out. If I throttle back after getting on plane and then trim up it starts porpoising after a very slight trim up.<br /><br />If I leave it at WOT after planing out and then trim up, as I said earlier, a tiny amount of trim will increase the rpm 500 or so to about 4,500. At this point the bow is still way down. Any attempt to trim past this point results in porpoising.<br /><br />The boat is rated for 200.<br /><br />Do you mean that I should continue to trim up even though it starts to porpoise and that it may pick up enough speed and have enough lift to hold the bow up? <br /><br />BTW, the boat I had before this one was a 1988 18' 10" Nitro bas boat, with a 150 Suzuki. I really liked that boat (not the Suzuki) and should have kept it. One thing I liked was how it handled in slightly rough water. I could run at moderate speed, about 3,500 or 4,000 rpm and trim the bow up, the boat would be fairly smooth and dry, riding on top of the small waves.<br /><br />As is, this Skeeter, at the same speed and rpm seems to want bow down operation only. With the same small to moderate waves, this Skeeter, with the V of the bow cutting through the wave instead of on top of it, makes for a wet ride. Trim up and porpoising in waves makes for a drenched ride.

 

[rla0248]

Re: Bass boat porpoising. Wrong set-up?

Oh I forgot.<br /><br />It was running on 5 only, but a change of switch boxes fixed it. It seems to be running perfect.<br /><br />Four of the cylinders have 123 - 126 compression. The other two have about 140. My next thread is going to ask if I should be concerned about the two with 140.

 

[rjolley]

Re: Bass boat porpoising. Wrong set-up?

take off the hydra foil, i had a bass boat that did the same thing, when you start trimming the foil is catching and acting like a wing and forcing the bow up and down as it catches the water.

 

[LubeDude]

Re: Bass boat porpoising. Wrong set-up?

Originally posted by rjolley:<br /> take off the hydra foil,

Ya, I would loose the foil also, your holeshot may suffer, but you are not getting the foil out of the water at the speed you are going and thats a problem. That boat power combination calls for "SMART TABS"! Depending on which transom you have, they may not work though.

 

[Ron G]

Re: Bass boat porpoising. Wrong set-up?

Have you tried running it wot and trim all the way up?with the 150 on it and a 23p prop you should be running 5600 rpms easy.if it blows out you may need to lower the motor alittle.

 

[KCLOST]

Re: Bass boat porpoising. Wrong set-up?

Where is the anti-cavitation plate (or your foil)height in relation to the very bottom of the hull????

 

[rla0248]

Re: Bass boat porpoising. Wrong set-up?

"Have you tried running it wot and trim all the way up?" No, I have had the boat out only a few times, and each time as I trimmed up a little it would start to porpoise and I would back the trim down. I'll try that next time out.<br /><br />Sting Ray is the brand of hydro-foil. I will measure the height of the hydro-foil tonight and report back in the morning, but I think it is pretty high.<br /><br />BTW, the NITRO I had before also had a hydro-foil and it never had any tendency to porpoise. I thought hydro-foil was a cure for porpoising, not a creator of it. Anyway, I'll try without it and see what happens, next time out.<br /><br />I should mention that all out top speed is not my goal. Mid range performance is more important to me. The boat should be able to run mid-throttle at 4,000 to 4,500 with the bow trimmed up. <br /><br />Do you think a prop with more lift is the cure? What causes porpoising? Is the current prop trying to lift the bow, but can't, so the bow falls, then it tries to lift again, falls again; creating the porpoising?<br /><br />What prop(s) would give good bow lift?

 

[Ron G]

Re: Bass boat porpoising. Wrong set-up?

Sounds like the skeeter is setup to do what bass boats are suppose to and thats haul butt to the fishing spot,try running it and when it starts porpoising increase throttle and trim you should run right out of it,and later you will start chimewalking more than likely.try this first,you probably havent drove it enough yet to get the full feel and how the boat reacts.like kc asked how high is the anticavation plate?and what brand of prop is on there now.

 

[LubeDude]

Re: Bass boat porpoising. Wrong set-up?

Originally posted by r_l_anderson:<br /> The boat should be able to run mid-throttle at 4,000 to 4,500 with the bow trimmed up. <br /><br />

Nope, not going to happen, maybe just a couple slight bumps of the trim is all you are going to get with the setup you have. Way too much nose sticking out there.

 

[rla0248]

Re: Bass boat porpoising. Wrong set-up?

Hi Bassin'Fever,<br /><br />The only comparison that I have is my other boat, the 1988 Nitro. It was set up similar to the 195 Skeeter, except that it had a 6" set back instead of 12" and it had a heavier motor (suzuki). The Nitro liked a like of trim, even at lower ranges. 4,000 rpm and up I could trim up quite a bit.<br /><br />I am assuming (and hoping) that this boat can be set up to do the same.

 

[rla0248]

Re: Bass boat porpoising. Wrong set-up?

KCLOST,<br /><br />The cavitation plate is 6" above the bottom of the hull.

 

[KCLOST]

Re: Bass boat porpoising. Wrong set-up?

Ok,<br /><br />12" setback, cavitation plate 6" above bottom of the hull.<br />I assume you have a low water pick-up on that lower unit...<br /><br />You can try raising it some more as long as you watch your water pressure and don't loose prop bite.... Go an inch at a time and retest...<br /><br />Make sure that the hydrofoil is out of the water at WOT... You will need a buddy to check that "carefully"...

 

[ufm82]

Re: Bass boat porpoising. Wrong set-up?

You have other issues apparently but a real good start to help eliminate this problem would be to put a 21 Tempest on that engine. Your WOT RPM is waaaay too low. Of course having only 5 cylinders hitting will not help that issue. However, the Tempest will hold the bow like no other prop IMHO. The prop shaft should be about 2 1/2"-3" below the keel and the hydro-foil should be gone. You are underpowered for that boat and may not be able to carry the bow with that engine but the Tempest will hook up better than the Quicksilver prop. The larger blades on the Tempest will give a better bite for the hole shot as well- you will have to experiment with the PVS plugs to get the best holeshot. Obviously the engine has to be running properly to get the boat to run right and you should be running 5400-5800 WOT on that engine. What block is that 150? <br /><br /> And how did a 1982 engine wind up on a 1999 boat? Sounds like a match NOT made in Heaven. <br /><br />Good luck with it. <br /><br />UFM82

 

[rla0248]

Re: Bass boat porpoising. Wrong set-up?

No low water pick-up.<br /><br />UFM82, it is running on all 6 now.

 

[KCLOST]

Re: Bass boat porpoising. Wrong set-up?

No low water pick-up....<br /><br />Well, that means that you are diffinitely limited on how high the engine can go....<br /><br />UFM82, may have a very good point! <br /><br />I would first make sure that the engine is running on all cylinders, fuel delivery is good, compression etc. And then experiment with various motor heights "carefully"... Keep an eye on that water pressure.... <br /><br />And a 150 on that boat is on the low end.... Just make sure it is running at it's optimum...