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Old 12 May 2012, 15:04   #1
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Leaking bottom engine bolts

Hi.

We have a 4m rigiflex with a Honda BF40 on the back.

The rigiflex is a plastic double hull (airtight inside) and so the engine mouting bolts come through the outer layer of plastic, through the air inside of the hull and then out the 2nd piece of plastic before exiting through some reinforcement material on the inboard side.

Orange is hull plastic, grey the reinforcement material and blue the water.



The problem we have been having is that when coming off the water we have found the inner hull to have rather a lot of water inside it and we rather suspect it's the engine bolts that are submerged. The engineers say they have tightened and resealed but water is still getting in.

Do you have any suggestions as to how we stop this water?

Thanks
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Old 12 May 2012, 17:19   #2
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How much water are we talking about? You really shouldn't get much more than a trickle, unless you're shipping water in rough weather and it's getting in elsewhere, such as anchor locker hatch, deck fittings, etc. When the bolts are fitted, then use Sikaflex 291. Probably best to use new bolts. Coat the hole aperture and bolt thread. Use stainless penny washers inside the transom for additional support. I know some recommend that you don't torque the engine bolts while the sealant is still curing, so that it compresses to form a better seal. Personally I'd just torque them. Wipe of excess Sikaflex with white spirit. I'd fit the nuts on the outside and one inside (for the outboard lock).
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Old 13 May 2012, 06:56   #3
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I think you need to fit compression tubes over the lower bolts as when the bolts are tightened the two skins will be pulled together.

If you measure the distance between the skins and get some stainless tubes made to slide over the bolts so as they are tightened the two skins are held apart but locked together . If this is done along with plenty of Sika then your problems should be solved....

Hope this helps.
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Old 13 May 2012, 08:28   #4
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Butty do you mean at the moment they are being pulled together and that is why it is leaking? It is a shame there is not solid material between the plastic skins to stop the problem.
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Old 13 May 2012, 11:58   #5
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If the two skins are separate and there is a void between them I suspect they are being pulled together and there is movement on the bolts.......

With out seeing I can't say, but it's what I suspect.....
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Old 14 May 2012, 14:13   #6
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Ok, leak has been fixed, thanks for the help.

Problem number 2 - inner hull has rather a large quantity of water inside it which refuses to drain off when tilting boat to stern. Any ideas how to remove it?

Thanks
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Old 14 May 2012, 14:58   #7
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put a drain bung using the screw thread version.
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