Porposing

[stickflipper]

If my motor cavitation plate is 2" below the transom will it increse the porposing effect? If I raise it will it help?

 

[IBrokeMyFreakinNeck]

Re: Porposing

Originally posted by stickflipper:<br />If my motor cavitation plate is 2" below the transom will it increse the porposing effect? If I raise it will it help?

Stickflipper,<br /><br />I'm sure the guys here will need more info on your set up. Boat size, motor size, prop size, etc. to be able to give you more accurate advice. Or maybe not, just my 2 cents

 

[stickflipper]

Re: Porposing

I have an 03 Crestliner SuperHawk with a Merc 115 2 stroke. I think the prop is a 19 pitch.

 

[JB]

Re: Porposing

It will surely help your speed to have the AV plate at the correct height, flipper.<br /><br />Are you experiencing porpoising? Do you have power T&T? How are you using it? When does the boat porpoise?<br /><br />This is not an engine trouble, so I am moving it to General Outboard.

 

[stickflipper]

Re: Porposing

It does have power T&T and I am using it to plane out. It seems that I must trim it so the motor is under the boat to get it to stop porposing at WOT. The motor is the Saltwater version with the 25" shaft. I have been told to put a Stingray Hydrofoil on it and it will help. Any suggestions?

 

[Hasbeen]

Re: Porposing

Raise the engine to where the cavitaion plate is even or just stighly above the bottom of your boat! The Porposing issue is due to too much trim and not enough power! Adjust the trim at WOT down untill it stops! Usually you cannot trim the motor much unless you are at WOT or you will experience this wonderfull feeling!

 

[walleyehed]

Re: Porposing

HasDude-BeenLubed has it right....engine needs to come up at least 2 holes (1-1/2") which is making me think you have a 25" shaft engine on a boat designed for a 20" shaft...can you give a measurement from top of transom to bottom of keel center???

 

[KeltonKrew]

Re: Porposing

I have been told to put a Stingray Hydrofoil on it and it will help. Any suggestions?

Don't do this if your motor is too low. I know from experience that this won't work, create more drag, etc.<br /><br />I have a 20" shaft outboard on my 15" transom and the motor was about 1" below the bottom of the hull. With the hydrofoil, it casued so much of a draw it was pathetic and had trim issues.<br /><br />I'm raising my engine and foil came off. Raise the outboard to the correct height BEFORE doing anything else. Then look at the smart-tabs here at iBoats.

 

[rickdb1boat]

Re: Porposing

As the others said, Raise the motor first and see if that solves your problem and go from there. It is WAY to low right now. As Kelton said, Trim tabs can help alot, but you need to get the lower unit at the right height first....

 

[WillyBWright]

Re: Porposing

The SuperHawk comes in 16, 17, 18, and 20 foot lengths. Only the 20' has a 25" transom. The 17' is rated for 125 Hp, so I'm guessing that's the one you have...but that's just a guess. If you have a 25" model motor on that boat, raising it to the highest settings on the clamp bracket may not be enough. I wouldn't put a jackplate on that transom to get the remaining height. You need the right motor. I'd consider the jackplate if you have an 18', one with a short setback.

 

[rickdb1boat]

Re: Porposing

Measure the shaft length:<br /><br />

 

[luise]

Re: Porposing

ok, the jist, porposing is what happens when the boat is either under-powered to acheive stern-lift or it is just too stern heavy. also an untrue keel like a hook in the hull would aslo be a contributing factor. try shifting some weight forward to bow, try a bobs machine broad-tail, or just gimme a dog-gone call. Luis<br />813-784-5025.

 

[stickflipper]

Re: Porposing

The distance from the top of the transom to the bottom of the keel is 25" The cavitation plate sits about 1.5" below the keel. If I move the Motor up to far what will it do to the boat then? I see that the dealer used a white rubbery sealant around the bolts holding the motor on. What should I use when I move the motor up? What type of support do I use to lift the motor to reposition it? Will changing the pitch on the prop to a 21 help?<br /><br />P.S. Thanks for all the help too!!!!

 

[tailfin10]

Re: Porposing

I am sure these guys are right about setting up<br />the motor correctly but.......My bass boat rated<br />at 130hp has a 115 ,heavy in the stern (three batteries and all)with two fat men and a full tank of gas would not jump on plane well, popoised unless you messed with the trim a lot,<br />had to trim a lot when turning.Tried Stringray<br />xp ,does not even seem like same boat.Jumps on plane,stays on plane at lower speeds,have basically only two trim positions I use,Does not blow out prop on turns and I dont even change trim,added two miles per hour too my top end.

 

[walleyehed]

Re: Porposing

Tailfin10, your experience is typical of an underpowered boat........been there, seen it, got the T-shirt....<br /><br />Stickflipper, I hate to say this, but you have the wrong shaft length engine on your boat....The only way you will ever get the most from that set-up is going to be with a jackplate.<br />Was this a package deal????<br /><br />EDIT: I stand corrected....YOU HAVE THE CORRECT ENGINE SHAFT LENGTH!!!!!!<br />I'm not going to delete the part above as I want to prove I am human too......

 

[stickflipper]

Re: Porposing

Yes it was a package deal. I have three holes left to move the motor up so I guess I'll try that first. I have been looking at a Four Stroke to trade into anyway. The 115 has enough power and the RPM for this engine is 5200 and I can get at least 5600-5700 RPM if I'm not watching the tach.

 

[walleyehed]

Re: Porposing

5600-5700 would be the correct WOT RPM if you are by yourself with a light load.<br />Test one hole at a time...keep an eye on the RPM, and do some trimming....see what the nose does.

 

[Boilermaker]

Re: Porposing

WALLEYEHED>>>I'm a little confused here (like thats something new )>> <br />You stated that he has the wrong shaft length engine>>>But he posted that he has a 25" shaft Merc 115, and that the transome messured 25" from the keel up. Also he states that the anti-vent plate is 1 1/2" below the keel.<br /> Doesn't the 25" shaft engine belong on a boat with a 25" deep transome??? Is it just that he needs to work on his setup more (like raising the engine to have anti-vent plate even with the keel??? I don't want to seem like I'm nitt-pickin', I'm just trying to learn whats right.<br />Thanks<br />Jim

 

[walleyehed]

Re: Porposing

BM, Good call!!!!! I messed that one up BIG TIME.....I think I'm spending too much time watching too many posts.....<br />You're on the money, Boiler....engine needs to be set-up with AV plate at least level with bottom and in most cases, a little above....the higher the better as long as you aren't ventilating substantially....<br />Thanks for the heads-up!!

 

[rickdb1boat]

Re: Porposing

Hi Ken,<br />don't ya just love it when you get things all turned around? I have that problem, also. Sucks, but no damage. someone is always there to correct you, thank god. Keep on with the good advice and don't worry about the occasional brain freeze. Happens to me all the time...