Leaks at Propshaft Strut Screws

[b-rad]

I have a new small leak (its not new, its obviously been leaking for a long time but I just noticed it after fixing my hemoriging stuffing box)
There are 6 small bolts where the prop strut bolts come through the floor.
4 of the 6 were loose loose, I tighted them up but they stll have a slight leak, they leak more when then the prop is spining. Should there be a seal on these? I was under the boat and I can only see one screw head the rest are covered with paint/or is it glass? Any advice on steming the leak?

[neilpride]

Hi, yes there is a way to stop the leaks, pull the boat out of the water, take off the screws and rebeding the screws with 3m5200, becarefull if your hull is a cored one, any long lasting leak there and the core is going to be wet, not a big deal , just the pain to put the boat in the travelift. Cheers.

[Boracay]

It sounds like the bolts have worked loose over time.

The best repairs are normally done by an experienced marine professional. If discussing the matter the following could be considered.

If the boat can be removed from the water it may be possible as a temporary measure to clean the area so as to remove all grease, carefully remove the nuts one by one, place oversize washers or backing plates with a suitable "mastic" (or maybe even a "rubber" pad) under them, on the bolts and to carefully redo the nuts.
The boat really needs to be out of the water as a minor problem could convert a small leak into a very large leak.
While temporary measures may be effective the long term solution probably involves removing the strut next time you haul (In the mean time keeping a careful eye on it, minimizing use of the engine and not leaving it too long - no big trips until fixed), drying that section of the boat (inside and outside) and epoxy fibreglassing a thick patch over the whole area on the inside and feathering it at the edges.
Then redrill the holes and rebolt, using oversize washers or backing plate(s) with a suitable mastic under strut and washers/backing plates.

Other members may have may have more relevant experience than mine so hopefully they will comment.

[osirissail]

Originally Posted by neilpride

Hi, yes there is a way to stop the leaks, pull the boat out of the water, take off the screws and rebeding the screws with 3m5200, becarefull if your hull is a cored one, any long lasting leak there and the core is going to be wet, not a big deal , just the pain to put the boat in the travelift. Cheers.

- - To add to the best advice above - REPLACE the screws/bolts - do not use the old screws/bolts. The leaking water over time has probably caused corrosion of the metal (especially if they are stainless steel). Also after removing the screws/bolts dry the holes by blowing hot air through them for a good period of time. The new T-5200 bedding will not adhere to wet surfaces.
- - It is a semi-serious situation to get them replaced if the leak has been going on for 6 months or more. If your prop strut is bronze use bronze screws/bolts. Avoid mixing metals when possible to help slow/stop electrical currents eating away your strut or screws/bolts. If you cannot find Bronze bolts locally they are available from: Boat Building and Woodworking Supplies
- - This is not a rocket science job - after removing the boat from the water, put a support under the strut to the ground and then remove the screws/bolts; clean and dry the holes; and put in the new bolts. You have a better chance of doing a conscientious and good job by doing it yourself.
- - If the leak is new and you are a long way from a regular haulout you can try underwater epoxy to seal the bolt heads - but - that is taking a big risk/gamble that the strut will not come loose/off and do serious damage to the prop shaft, prop, or hull of the boat, including your shaft log.

[b-rad]

So do I have this correct? The strut should be sealed to the hull with 3m, then the rest of the strut should be glassed in then painted? There are some large washers ( 3/4 inch) around the screws do these have a rubber seal on the bottom?

[osirissail]

- - Normally the strut is bedded just like a lifeline stanchion - T5200 between the hull and mounting face of the strut and then you coat the machine screws/bolts with T5200 and push then through the hull. But first all the surfaces need to be acetone wiped to got all grease, and other contaminants off the mating surfaces.
- - The inside the hull a backing plate is bedded to the interior of the hull and the machine screws/bolts pass through it and then I normally use fender washers with T5200 on the bottom and then a lockwasher and finally the nut. Everything is torqued down good and hard. If the strut and backing plate are not showing any leakage it is not necessary to remove them. Just put in new bolts with bedding.
- - As a quick fix you could remove one nut and washers inside and clean them and put new T5200 and reinstall them. Never should you have anything rubber between the washers, nut and the backing plate. The strut needs a "hard" mount against the hull to prevent any vibration or movement of the strut.

[shakey doug]

Job best done out of water, check strut bearing & alignment then release strut bolts strut may need packing for alighn ment -clean area with acetone apply copious qty sikaflex or similiar same deal in side useing large od washers plus nyloc nuts or s.pring washers .Once tensioned recheck alighnment, any excess sika can be profiled useing a little washing up detergnt on finger for 120% job glass over inside area not many do .Shaft alighnment most critical could be cause of problem in the first place.

[b-rad]

Ive decided to have the boat hauled, to many little things adding up to keep patching. So hopefully in about 2 weeks I have a boat with no leaks a well mounted strut and fresh paint.

[mike d.]

do not use 5200 to mount and or seal the strut and bolts once cured they will be almost impossible to remove if you have to later on for service or if strut got dmgd. use 4200 or poly-sulfide. 5200 is an adhesive not a bedding compound

[osirissail]

The reason T5200 is used is that it will stick to things that are not absolutely clean better than other sealants. If you take care to really make sure everything is clean and no grease or water or whatever is on the two mating surfaces then non-adhesive bedding compound are the way to go. It is all a matter of time and effort. For best results using non-adhesive bedding compounds do not fully tighten down the parts being joined until the bedding compound is cured. Then fully tighten down the bolts. The idea is to form a "rubber-like washer" that you can squeeze a little when finally tightening the bolts. With T5200 you put it on and go right to fully tight and then clean up the excess material with kerosene or paint thinner and paper towels.

[Cheechako]

Do it right. Remove the bolts and loosen the strut from the hull, clean the hull pad and strut really well, replace the bolts and nuts with bronze ones (assuming the strut is bronze) use large heavy fender wahsers inside the boat, put a bunch of 5200 between the hull and strut, bolt it up by tightening each bolt a little, take your time letting the 5200 ooze out, just keep working it. Clean up the excess 5200, wait overnight or a few hours and then one more retightening.

[gonesail]

make sure the water isn't coming from somewhere else .. like it was on my boat. i thought the strut was leaking but instead some rain water had blown into the stern.

[neilpride]

Originally Posted by mike d.

do not use 5200 to mount and or seal the strut and bolts once cured they will be almost impossible to remove if you have to later on for service or if strut got dmgd. use 4200 or poly-sulfide. 5200 is an adhesive not a bedding compound

Use 3m 5200!! i know is a hard stuff, dificult to remove , but in underwater fittings is the best stuff, almost all the fin keels trough bolted to the hull use 5200 , be sure all the surface is clean , Cheers.

[Cheechako]

yep, do it once.... permanently!! I cant think of a single thing I've bedded with 5200 in the last 25 years that leaked... portlights, hatches, thru hull fittings, struts, deck hardware etc....

[b-rad]

Last question guys (yeah right) I did some swiming today to tigthen up the bolts so I could make it to the yard next week. The strut was glassed in at some point, but It has cracked around the strut and was easy to pull off pieces of glass/ expoxy.
I dont know anything about fiber glass and really dont want my first project to be something that I would have to pull the boat back out to fix so I am going to have the yard fix it. This is a identical boat

What is used to glass that in?