View Full Version : Waterproofing

03-08-2006, 09:56 PM
Can anyone give me expert advise on how to replace the silicone bead around my boat, 1985 Prostar 190, I have a leak on front right side when taking hard right turns. I'm sure it is coming in through the seal at the bumper bead. It looks like it has been repaired before but the silicone was not wiped down so I know it was a patch job.

Should I take the entire bumper off, clean the surface then re-caulk the entire boat? What can I expect to find, what should I look for and what is the best way to fix it?

Edwin Fuqua

03-08-2006, 10:30 PM
I'm not your expert, but will bump to the top. I wasn't aware of a silicon bead during manufacture, but maybe there is. What I remember from the factory tour is stainless steel screws every 6 inches around the boat holding the top and bottom together.

I looked as I've heard this problem on here before, but never heard the solution.


03-08-2006, 10:35 PM
Depending on the condition of the rub rail, you may just want to remove it and replace it. Then you could rechaulk the whole rail.

03-08-2006, 10:47 PM
Where the hull goes up inside the deck where the rub rail mounts on most most models[maybe not the newer boats], the factory ran a bead of silicone along the bottom of the rub rail onto the hull and smoothed it out. When we put our brand new '89 in the water the first time it leaked like crazy and I discovered they forgot to do the silicone on my entire boat during assembly. SO, I did it myself with GE MARINE GRADE CLEAR SILICONE from a local boat dealer. It has never leaked in the 17 years since!

03-08-2006, 10:49 PM
If you don't want to remove the rubrail, run a bead of silicon under the rail where it meetes the boat. Like always when runing a bead, run you finger over the silicon to smooth it out.

Remember: it is easier to put more on then to wipe off extra.

03-08-2006, 10:51 PM
Thanks TMC#1, learned something new!

03-23-2006, 09:06 PM
Hey, thanks for all the answers and suggestions.
I'll take them all in consideration but I have discovered something from an email from the Mastercraft tech. department and from talking to Ken Johnson at an Atlanta MC dealership/service center. He said that the silicone caulk below the bumper was a fast fix for the problem. He advised to take the bumper off (resuse or replace) but while it is off clean and silicone the area where the top and bottom comes together. Let the caulk dry and replace the bumper. He said no silicone is supposed to be exposed outside of the bumper. Now I know I could clean the area where it is leaking and when the caulk is applied use (this is important) denatured alcohol and a cloth (just like cleaning latex caulk with water) and rub the bead smooth. That's a little trick nobody mentioned but I know. Look at the bead in a fish tank, thatís how they get it so smooth.

Anyway, I think that is how I'm going to proceed.

I just found this thread, did not know how to get back since I created it. Still learning the system but find it totally usefull and fun.

Edwin Fuqua
[email protected]

03-23-2006, 09:25 PM
I did mine this year. I reused the rub rail, but took all of the rivets out and used stainless machine screws and lock nuts. Make sure to get all the old caulk out, and cleaned good. I used a screw driver over a rag with alcohol to get it clean up inside. Look under rub rail in the threads, there are a few in there.

04-13-2006, 09:31 PM
Ok, now the crap has been taken out of the old joint.
We are putting in new stuff, simular to old silicone but newer. I suggested urathane chaulk like NP 1 (made by sonolastic) but my friend said use the urathane chaulk that is used on Corvett's. I checked w/ Ken Jonnson (local dealer/ service tech) and he said OKay too. I think it is the same but the GM stuff is clear. So be it, I will post some pictures soon and I hope all will be good too.
Edwin Fuqua

04-15-2006, 03:34 PM
In the case above where urathane chaulk, or urathane windshield sealant is used alcohol will not clean it up. You must use a urathane solvent or reduser and use it just like the alcohol cleanup suggested above with silicone.

Anyway I have left the rivits in that attach the top to the bottom and I will pry up the fiberglass to finish cleaning and to apply the urathane sealant. This should fix the old problem and I'll be back thundering on the water soon.

BTW, my wife decided she does not like my boat and she bought a Glasstron w/ a 4 cly Cheveolet. I guess that is a good taxi and will get good gas going to Clemson and Martin for something to eat, etc. I know the little girls will like it because it has a bow ride area. I still like my MC ski boat but we'll all have fun.

05-03-2006, 12:03 AM
In reply to your message and including additional information I would like to ask a question. Urathane sealant is abundant, I have some UP-1 adheasive/chaulk and I had a technical data sheet for it but now I can't find it. The chaulk other than up-1 is this stuff found at http://www.camaros.net/forums/showthread.php?p=21165 that is used for corvett/chevrolet windshields and body adhesive. The main difference I can tell is the UP-1 is white the chevrolet stuff is clear and do you know which would be better?

I've spent a lot of hours cleaning the grove between the hull and the deck. I haven't removed the rivits joining these two yet. I'm not planning on doing that either but it is really going to be hard to get the chaulk into the tiny little groves around most of the boat.

I wish I had the link to the UP-1 I'll try to get that here as soon as I find it.


05-03-2006, 12:21 AM
Hey the sealant is NP 1 not UP 1. The link to their site is


sorry for the error above.


06-03-2006, 11:59 PM
Well here are some pics of the seal. The stuff was black and we tapped off the area we did not want to get the gooey stuff on.

It don't leak anymore but I don't know how to attach the pics.

Trying here: I'll try somewhere else.

06-04-2006, 12:16 AM
We went out last weekend and all had a really great time. We came across this Tunnel Hull/ Cat boat that I am really interested in hearing more about. The name of the boat was the Tennessee Cat? Big.

Anyway anybody got any info on this guy... 40ft, twin blown, bad and very loud. Matter of fact the driver and throttle girl (wheew) were wearing hearing protection. In lake Hartwell, GA.. wish I had my camera.

I want to upload photos but I can't or don't know how I don't have photos of the cat but of the MC in it's recaulk. Hopefully this will give'em to you.

Well I tried. guess I'll have to put them on my server and give you a link.... that will be http://computeralarm.com/boat/454.htm

for now,

06-04-2006, 07:59 AM
Wow - great shots. nice looking umm.... boat.;)