what are the fins coming off the sides of transom

i have another dumb? i was looking at skinning the bottom of my toon and keep seeing these fins "i will call them " on the sides of the transom be for the motor.if you look up underskinning in this forum and find pics you will see what im talking about! are they lifting strakes or do you know what they are and what purpose they do?

Re: what are the fins coming off the sides of transom

Why don't You post Pics?

Re: what are the fins coming off the sides of transom

Those are to keep the water channeled downward to help prevent ventilation.

Re: what are the fins coming off the sides of transom

EGlideRider said:

Those are to keep the water channeled downward to help prevent ventilation.

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so they dont have anything to do with lift at speed? i have a 18' party barge with a mercury 4 stroke 40 hp ,do you think they would help out at all? seams the water lines on side of pontoon go up a good ways on back of toons .would it help to lift back up any or would it be a waste? i have checked for water in toons but to the best i can tell they are empty and boat doesnt lean to a side.
DSC07670.JPG

Re: what are the fins coming off the sides of transom

July 18th, 2010 09:31 PM DSC07670.JPG

Re: what are the fins coming off the sides of transom

would if i new how to do it.hate computers! can never do what i want it to

Re: what are the fins coming off the sides of transom

They will provide some lift at speed but the lift is insignificant. I would assume you already have these fins on your transom because most pontoons do. Did a particular problem or concern prompt your post?

Underskinning and lifting strakes on an 18', 40hp is a waste of money because you will notice no improvements in performance and, in fact, probably a decrease in performance due to the added weight.

Re: what are the fins coming off the sides of transom

If you talking about the short ones on the transom (as opposed to lifting strakes which are welded on the sides of the tubes), I've always known them as "Splash Fins" that prevent water from shooting upward when underway..

Splash Fins

Re: what are the fins coming off the sides of transom

Yup, those are splash fins and they don't provide any lift at all, just there to help control the water at the back of the boat.

Re: what are the fins coming off the sides of transom

I full skinned My 2005 20 ft forest river, 60 hp 2 stroke yamaha and I added a .125 alu piece to the bottom of the motor pod that adds 2.5 sq ft lifting area to the bottom of the pod below the splash fins. The 105 lbs. of skin addition did result in slower speed but the decrease is approx 1/4 mph. The small engine pod increase in bottom area also, does not help the speed but does result in an almost level attitude at WOT. I may drill out the pop rivits and remove the pod lifting pad addition. The only good from the pod pad addition is a small increase in speed if I load all gear and passengers aft. My normal WOT speed with 3 people is 20.0 mph GPS. I may have some speed increase running against 18 inch swells from the skinning job but to date, no swells. Fuel milage is good at speeds 5 mph and under and also a good cruise milage at 12 to 15 mph

Re: what are the fins coming off the sides of transom

I think I would also remove the "lifting pad" from the transom. Probably makes for a slightly rougher ride and if it ever tore loose, it could be bad news. 20 MPH with 3 aboard is very decent..

Re: what are the fins coming off the sides of transom

EGlideRider said:

They will provide some lift at speed but the lift is insignificant. I would assume you already have these fins on your transom because most pontoons do. Did a particular problem or concern prompt your post?

Underskinning and lifting strakes on an 18', 40hp is a waste of money because you will notice no improvements in performance and, in fact, probably a decrease in performance due to the added weight.

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The splash fins do provide a very small amount of lift. The other reason for them is the reduce splash at transom, which will reduce some water drag. Look under at speeds and you'll see how they help. To say that underskinning an 18' toon is a waste, would be misinformation, you'll get a smoother ride and a few mpg/mph from doing so. The weight is small compared to benifits. I have seen nothing but sucess with underskinning. And at Lake Cumberland there are hundreds of pontoons.