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Bottom Paint slowing me down?

Old 10-06-2008, 05:37 AM
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Default Bottom Paint slowing me down?

I've got a Scout 17.5' Costa. It's got a '97 90hp Honda on it. The previous owner had the boat sitting in the water for about a year. So he bottom painted it.

I drove the boat quite a few years ago before he bottom painted it and it seems like the boat could move pretty good. It never jumped up on a plane that quick but I always attributed that to it being proped incorrectly or just being an earlier 4-stroke.

Now the boat is all sorts of sluggish. Even at WOT it feels like its barely pushing 30mph. Though I haven't clocked it yet. Seems like it used to hit 40mph or better pretty easily.

Could it be the bottom paint making that big of a difference.
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Old 10-06-2008, 05:50 AM
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Default Re: Bottom Paint slowing me down?

Well, you're not being very scientific with your comparison. Unless you really know the speed it used to make, and the speed it makes now, there's nothing to compare.

Is the boat kept in the water or out? Is there marine growth on the hull or running gear? What type of bottom paint and what condition is it in?

The boat might have an engine problem or a prop problem. You might have gained a few pounds.

I don't think bottom paint would cause a 25% loss of top speed.
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Old 10-06-2008, 05:54 AM
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Default Re: Bottom Paint slowing me down?

its not the paint. maybe you need to still clean your bottom, but its not the paint. I've said it before, you have a 17' with a 90 hp...if you were dragging a full can of paint behind the boat you should hardly feel it. a layer of paint applied thinly over the whole bottom will make almost ZERO difference.

Now if you have not maintained your bottom and crap has gotten a hold of it then yes, there is your problem. but it is not the paint itself slowing you down.
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Old 10-06-2008, 05:58 AM
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Default Re: Bottom Paint slowing me down?

It's on a trailer now. There's no marine growth at all. No tellin what kind of bottom paint the previuos owner used.

The engine has been fully tuned.

Sorry for my lack of scientific process. I'm really just relying on what myself an others who know the boat have noticed about it.
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Old 10-06-2008, 06:02 AM
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Default Re: Bottom Paint slowing me down?

Can you get us compression numbers for the motor? That would be a big help trying to decide whether this problem is propulsion or physical.
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Old 10-06-2008, 06:03 AM
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Default Re: Bottom Paint slowing me down?

When did you ride it last?

1997..... 11 seasons......
Hmm, the boat may have gained some weight, the motor may have gotten a little tired, and layer upon layer of bottom paint will make a noticable difference in performance...
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Old 10-06-2008, 06:06 AM
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Default Re: Bottom Paint slowing me down?

I'm think it's possibly the motor getting tired. The previous owner was a very wealthy individual who didn't give a damn about it for the most part. He didn't even know he needed to add hydraulic fluid to the trim/tilt motor.

I'll look into the compression test.
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Old 10-06-2008, 06:09 AM
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Default Re: Bottom Paint slowing me down?

CThomps - 10/6/2008 9:06 AM ............ He didn't even know he needed to add hydraulic fluid to the trim/tilt motor.............
Me neither
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Old 10-06-2008, 06:09 AM
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Default Re: Bottom Paint slowing me down?

Afishinado - 10/6/2008 9:03 AM

When did you ride it last?

1997..... 11 seasons......
.......................... and layer upon layer of bottom paint will make a noticable difference in performance...
I don't think he said there were multiple layers, but even if there are, a 25% loss in speed?

I would think that if the surface is smooth, the number of layers would not make a big difference. 2%, 5% loss maybe. Not 25%.

It has to be the engine, prop, or his method of measuring performance.
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Old 10-06-2008, 06:12 AM
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Default Re: Bottom Paint slowing me down?

10% Difference on a boat that 40 is noticable (I never said 25%) and presume he painted the bottom every year... What years did you skip?
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Old 10-06-2008, 06:14 AM
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Default Re: Bottom Paint slowing me down?

Afishinado - 10/6/2008 9:09 AM

CThomps - 10/6/2008 9:06 AM ............ He didn't even know he needed to add hydraulic fluid to the trim/tilt motor.............
Me neither
Well, you don’t actually add it to the motor, you add it to the trim pump reservoir.
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Old 10-06-2008, 06:19 AM
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Default Re: Bottom Paint slowing me down?

Afishinado - 10/6/2008 9:12 AM

10% Difference on a boat that 40 is noticable (I never said 25%) and presume he painted the bottom every year... What years did you skip?
From his statement "The previous owner had the boat sitting in the water for about a year. So he bottom painted it.", I'm assuming one coat of paint.

It's early in the morning, but he said he thought it used to do 40 MPH and now it does 30 MPH. I think a 10 MPH loss from 40 MPH is a 25% loss but like I said, it's early in the morning (for us retired folks anyway). Math never was my best subject in school.
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Old 10-06-2008, 06:21 AM
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Default Re: Bottom Paint slowing me down?

Ok, I give....
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Old 10-06-2008, 06:43 AM
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Default Re: Bottom Paint slowing me down?

Engine problem or boat is full of water. That boat with a 90 should fly, Scouts are light.
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Old 10-06-2008, 06:46 AM
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Default Re: Bottom Paint slowing me down?

Can bottom paint be removed or do I just have to wait forever for it to wear off?
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Old 10-06-2008, 06:48 AM
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Default Re: Bottom Paint slowing me down?

Afishinado - 10/6/2008 9:21 AM

Ok, I give....
The real variable here is that he thinks it used to do 40 MPH several years ago and he thinks it only does 30 MPH now. He never clocked it several years ago so there's nothing to compare it to even if he clocks it now (except an identical boat and motor combination).

He can have the motor checked (not just "tuned) and he can try different props. He can inspect for hull damage, and if he wants, remove the bottom paint.

After all that, it is what it is.
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Old 10-06-2008, 06:50 AM
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Default Re: Bottom Paint slowing me down?

CThomps - 10/6/2008 9:46 AM

Can bottom paint be removed or do I just have to wait forever for it to wear off?
Yes. With chemical stripers and/or sanding. There have been posts on soda blasting and it seems most posters were not happy with the results.
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Old 10-06-2008, 06:59 AM
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Default Re: Bottom Paint slowing me down?

Has anyone tryed citristrip or soygel? Will chemical strippers damage the fiberglass?
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Old 10-07-2008, 10:01 AM
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Default Re: Bottom Paint slowing me down?

So I ran my hand across the bottom paint and it's rougher than 80 grits sand paper.

Will a palm sander work to grind it smooth?
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Old 10-07-2008, 10:47 AM
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Default Re: Bottom Paint slowing me down?

CThomps - 10/7/2008 1:01 PM

So I ran my hand across the bottom paint and it's rougher than 80 grits sand paper.

Will a palm sander work to grind it smooth?
Yes.

The dust is toxic. Don't inhale it, don't get it on your clothing and then get into your vehicle, don't bring them in the house without washing them first. Or wear disposable coveralls.

Don't get it into the environment. Collect it and dispose of it properly.
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