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  1. #1
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    pontoon boat porpoising - need help?

    I have a Mercury Verado 350 on my pontoon boat and it orpoises like crazy after 46mph. Ughhh! I need a recommendation for a good prop-shop to help me get rid of my porpoising problem. Any help would be appreciated.

    Phil

  2. #2
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    What kind of pontoon? Flat? Round? Strakes? An irregular or flexing running surface can cause porpoising, among other things...
    '89 Hydrostream Vegas XT, '90 Merc 2.4 Bridgeport PCU EFI
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    Quote Originally Posted by pyro View Post
    What kind of pontoon? Flat? Round? Strakes? An irregular or flexing running surface can cause porpoising, among other things...
    It's a Playcraft 27' Extreme with a 5' stepped hull. There are only two of them built so far and hull #1 doesn't seem to porpoise like mine. The owner who is also a dealer out west has a problem with me for some reason and refuses to discuss how he solved the problem. The factory people refuse to take my calls or help me. They tell me to call my dealer ... who doesn't have the foggiest idea how to solve the problem. I have been performance boating for over 50 years now and have never experienced this animosity to helping a fellow boater with the same brand. Oh well, it takes all kinds.

    The tubes are round with the center tube being 27" and out the outer tubes 23" (I believe). The boat has lifting strakes which make it faster than other toons. The toons are very rigid and do not flex to my knowledge.

    After talking to some prop people, they say that the prop seems to not be holding up the nose and lets it fall down every time my trim brings it up. I don't think this is right. Based on my extensive tunnel boat experience, it seems to me that the porpoising is occurring because the air is trying to bleed out the sides and can't find a place to go. This is what always happened to my triple outboard 32' Skater. What a nightmare this was until you could get the Skater really tunneling. My 28' Skater did more or less the same thing. However, my 25' Talon never ever porpoised at any speed. Neither did my 36' Spectre (well not hardly at all). Neither did my 21' Jones Tunnel which was the second best boat I ever owner (R.I.P. Manta).

    I am thinking about sending the prop back to Mercury Racing for a lab finish. Until I can solve the porpoising .. at least I will get some more 'R's while I am using negative trim.


    Any suggestions or do you know a really good prop man?


    Thanks,

    Phil

    PS - Years ago I used to use Mike Spinelli or Mercury Racing or Jeff Titus (he was the best of the best, but doesn't know how to solve my problems).

  4. #4
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    sounds like your a very experienced performance boater! all the same theories apply!a little more detail about the setup might help with porpoising solutions!what prop,setback,jackplate?,loaded vs. nonloaded reaction,is this a full center tube or 3/4.
    any option for weight relocation,batteries,gear?
    I see these boats were also rigged as an I/0 and was the huge outboard weight location not considered in the tube design!

  5. #5
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    If the strakes are open on the back take an adjustable wrench and bend down the back of the strake. Start with a little bend and keep increasing the turn down until the porpoising stops. If the back of the strakes are sealed you can rivet or weld a torque tab for a lower unit to the bottom of the strakes. If you have a welder close by you can also weld a bead along the bottom back edge of the strakes.

  6. #6
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    MOTOR TOO HIGH OR PROP TOO BIG OR BOTH ...OVERTRIMMING, OVERJACKING, OVERLOADED, THIS AINT A SKATER OR SPECTRE OR A TALON ...YOU CANNOT USE THE SAME SETUP TO GET THE PONTOON TO RUN.
    PROP TYPE.. DIA/PITCH, MOTOR HEIGHT, SETBACK INFO IS NEEDED ....MAX RPM YOU ACHIEVE LOADED, MAX RECOMMENDED RPM FOR THE MOTOR?, IM GONNA GUESS IT IS OVERPROPPED, OVERJACKED, OR BOTH. TRYING TO GET THE RPM UP BY OVERTRIMMING? WHAT SPEED GPS? WHAT WAS THE MFG ESTIMATED PERFORMANCE? WHO WAS THE DEALER SOLD YOU THE BOAT ? WHY WONT PLAYCRAFT TELL THE DEALER THE PROBLEM ? DEFECTIVE BOAT? SOUNDS FISHY, WHY THE BAD BLOOD TWEEN YOU AND THE MFG/DEALER?
    I WOULD THINK PLAYCRAFT WOULD/SHOULD KNOW THE TRICKS TO GET THEIR STUFF TO RUN PROPERLY.
    Last edited by RIVERRUMMER 70; 02-17-2014 at 12:58 PM.

  7. #7
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    Your fastest speed will be with a prop that can hold the bow up. If you motor is two high no prop will keep your bow up. Just my experience with a bow heavy boat.Click image for larger version. 

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ID:	292540My prop shaft is below the Pad, my boat will run slower if the motor is raised.Where are you located?
    L.T.


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    You guys are terrific for responding to me so quickly and all with very intelligent questions. Most forums I am on people respond by first calling me an idiot until they find out that I am somewhat intelligent.


    OK, let me give you some background FYI:

    I am located on Smith Mountain Lake, VA which is a fresh water lake and is about 800' above sea level.

    My pontoon is a 2014 Playcraft 27' Extreme with a Mercury Racing Verado 350 which can turn up to 6,800RPMS according to Mercury Racing. I have a stepped hull which starts at 5’ from the transom. There are only two of these boats made so far by Playcraft. The Stepped hull has not affected the handling of the boat in any way expect maybe the porpoising. I say maybe because the non-stepped hull version porpoises somewhat as well above 46MPH.

    The engine on my boat is set back about 1' on the transom. It has a 20" midsection so the engine actually sits quite a bit lower than on my previous Playcraft 26' Extreme which had a 25” midsection adn was set right smack next to the transom and still porpoised at 46+MPH. Top speed on that boat with a 275 Verado was 47.5mph on its best day on my lake.

    I have experimented by moving the engine from the top hole, and then the next one down and the next one down and the next one down. So I am about 3 holes down (or up whichever way you want to look at it). I am still getting 25lb PSI at 30MPH. Theoretically, I could go up even further – probably another hole. None of these heights seem to have affected the porpoising however.

    My best run ever was on a perfect day at the end of October 2013 and looked like this:

    weight: myself only and bimini top up
    engine: Verado 350 (20" midsection)
    fuel: 15 gallons
    prop: Tempest 19P (bone stock out of the box)
    gear ratio: 1.75
    rpm: 6,500
    top speed: 62mph
    trim: absolutely flat
    slip: 7%

    I know there is another 200-300rpms there to be found because I ran 6,875rpms with my 4-Blade Rev4 17P which is over the limiter. I felt it bumping when I started to see 6,700+rpms on the tach.

    Using the same slip and upping the rpms from 6,500 to 6,700 it could potentially get me 65mph! That would be just unreal ... but I may not hit my 62.5mph again. You know how that goes. It could have just been a fluke. The good news is that this is probably the fastest single engine pontoon on the water, bar none! Yeah, I could probably go faster with a Diamond Marine 2.5EFT running 8,600RPMs

    I know I ran 58mph with 4 heavy guys in the boat and 50 gallons of fuel on an average day with my REV4 17P 4-blade. I know that is a far cry from 62mph but that is the real world. The boat still porpoised. Ughhh!

    If I trim the boat out a little more it simply porpoises more. As I run negative trim, the point at which the porpoising starts is a little higher MPH wise. In other words, I will start porpoising at 48MPH instead of 46MPH. I can, however, run 45MPH with little or no porpoising with the 4-blade. This boat runs best with neutral trim.


    That is the background gents, so here goes my thoughts and answers to your questions:

    I think the manufacturer won’t return my calls because they don’t have the solution yet. The dealer in the Midwest won’t return my calls probably because I didn’t buy his used boat from him and boat a new boat from another dealer. Also because he wants to be the fastest Playcraft on the water and doesn’t want to share his performance secrets. I can see this. Some people are like that as you know very well.

    LaveT - It makes sense to me that if I run the motor closer to the transom I should porpoise less, but the manufacturer has determined that the boat handles way better in the slop with the engine set back. … and it does based on my testing compared to my previous Playcraft. If I cup the 3-Blade prop more will that help hold the bow up better?

    Brian Harden - As far as the strakes go, your point is well taken and you are probably correct. Unfortunately, I can’t get to my boathouse to checkout the strakes until the snow clears … at which point I will examine the bottom of the hull carefully and get back to you. If there are no strakes to bend, maybe I can get some Torque Tabs welded on. That sounds like a plan to try.

    RIVERRUMMER – You addressed so many good points to consider. I’m not over propped because I am running a really good speed, however I need a good prop man to lab finish the prop and get me another 200-300RPMS. May, I need more cup to help hold the bow up? You don’t need positive trim to get this boat to run. It runs great and much better that I expected … of course you have to deal with the porpoising as you know. Playcraft makes a great quality boat. When people see it (black, orange and white) they are blown away especially with the 350 on the back. I just checked the Playcraft website and found the outer pontoons to be 24” diameter. I think the inner toon is a little larger.

    DonMac – It is interesting that you mentioned weight distribution. I have tried putting 3 people in the bow and it cuts down on the porpoising somewhat but then I lose the handling in rougher water (1’ to 3’). My wife says I need a big burlap bag filled with potatoes. I remember years ago, my friend Little Joe from Long Island ran a 15’ stream at 100MPH with his girlfriend and another person lying up in the bow of the boat. … and he trimmed it to the moon! Holy Cow Batman!

    I apologize for running off at the mouth here. I hope I told the story right.

    Thanks for your help guys,

    Phil

  9. #9
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    i play with tritoons a good bit and some boat companys put too many lifting strakes on them, it could be trying to lift the the transom out of the water causing the bow to fall down,usally this happens in the mid to lower 60s. because that are actually wedges, jmo tim

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    Quote Originally Posted by Spectre Man View Post
    Most forums I am on people respond by first calling me an idiot
    Idiot!!! (Just wanted you to feel at home)

  11. #11
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    Quote Originally Posted by transomstand View Post
    Idiot!!! (Just wanted you to feel at home)
    We can only call him that if he followed big Jhonson after drinking apple pie all day
    1990 hydrostream virage diamondpower280

  12. #12
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    Quote Originally Posted by timmc6 View Post
    i play with tritoons a good bit and some boat companys put too many lifting strakes on them, it could be trying to lift the the transom out of the water causing the bow to fall down,usally this happens in the mid to lower 60s. because that are actually wedges, jmo tim
    What single engine pontoons do you know of that run mid 60s.

    Interesting point however. I am going to check out the strake configuration as soon as the ice and snow clear. I know they are very proud of their bottom like all pontoon boat manufacturers. They all feel they have THE secret hlul design.

    Most of the manufacturers and dealers lie when it comes to speed. I was told by several manufacturers before I bought my Playcraft that their pontoon would hit mid 50s easy with a Verado 300HP. You know how this story ends; THEY ALL LIED! One manufacturers told me mid 50s and then when I checked with Mercury (who ran the tests), the boat only ran 41.6MPH. That is a far cry from mid 50s. LOL!

  13. #13
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    If the step is aluminum I would say the angles are not sharp enough to shed water. Happens a lot to glass mishandled by a stacked storage facility dulling a part of one of the strake steps. Tin just is never sharp enough out of the box sometimes.

    Oddball stuff: your catching Air and flopping up and down. Is it worse with a headwind?
    your pulling angle on the step and just not enough hull in the water to hold it up.

    Kinda guessing fastest we have here runs 50 55 fine not a playcraft.

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    Dale hollow lake,they are several here at the marina, this place is like tritoon proving grounds. Most of them have Suzuki power the 250 ss is a very powerful 4 stroke engine, ps,the u shaped toons with equal power are faster ,jmo after working on with them for a couple of years, moving strakes,shortening them up, the bigger diameter props like the Suzuki 16" dia the better,jmo

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    Seems most boats are rigged at the factory with the motor too low which also causes a porpoise. First thing I would do is play with engine height.
    13' Biel tunnel AKA "Flight Risk"
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