Hairline cracks in transom - help!

[Bobalong]

I own a 3.6m RIB which has a 25hp outboard. The engine is a 4-stroke with electric tilt/trim, thus it is right on the size and weight limit for the boat (82kg). The engine mounting plate is bolted through the transom in 4 places (top-right, top-left, bottom-right, bottom-left). The boat is about a year old, I have owned it from new, and the dealer supplied and installed the engine for me.

I have used the RIB for about 25 hours since purchase, of which maybe half has been on the plane, including on some slightly choppy sea with a few small "airborne moments". Today, having given the boat a good clean, I noticed some fine hairline cracks had formed in the gelcoat on the transom. I am rather concerned about these, hence this post!

If you are looking aft at the transom (i.e. from inside the boat), the transom is strengthened on each side by a box-section moulding coming up from the floor at an angle of about 30deg from horizontal, effectively joining the transom to the hull floor and acting as strengthening member. The cracks in the gelcoat are forming on the vertical intersections where the box-sections meet the transom. Also at the bottom of the transom there is a margarine tub sized recess for water to collect in, out of which water can exit the hull if the drain plug is unscrewed. A few hairline cracks in the gelcoat are visible where the transom meets the floor in the vicinity of the recess.

There are no similar cracks visible on the aft-side of the transom, although at the top-centre of the transom there is a slightly bigger crack running horizontally, where the top surface of the transom appears to have separated slightly from the rear surface of the transom.

Shortly after purchase I discovered that in the boat manual the stated engine weight limit was 65kg, although the dealer had supplied me with an 82kg engine. When I queried this he said the manual was wrong and sent me an updated manual with the weight limit raised to 82kg. Fair enough I thought! However, now I have seen the hairline cracks I am concerned that the engine really is too heavy for the boat and that the cracks in the gelcoat are possibly the first signs of overstress.

Has anyone on the forum seen this type of problem before? Also as I am not an expert in fibreglass, can anyone tell me if the hairline cracks in the gelcoat are just that, or are they a sign of some more serious damage underneath? I am rather concerned about it because if they get any worse I will have to invoke the 5-year warranty on the hull with the dealer, which could become difficult.

Thanks in advance for any advice.

[Rokraider]

Some photo's might help. What make of RIB is it?

[Bigmuz7]

Originally Posted by Bobalong

Has anyone on the forum seen this type of problem before? Also as I am not an expert in fibreglass, can anyone tell me if the hairline cracks in the gelcoat are just that, or are they a sign of some more serious damage underneath?

Welcome to Ribnet .. unfortunately in such a concerned circumstance .. there are plenty of threads here about this type of problem if you do a search .. not all end in tears .. pics are required for some views, but thats all theyll be.

Interesting to hear about your dealers change of literature, whats the outboard ?

[Fenlander]

As far as I can see the Excel website and all dealers selling this model still say max 65kg outboard. 82kg is quite heavy for a rib that only weights 115kg in total. Add in some shock loading from speed in a chop and the cracks might be expected.

I've had it before on older grp boats where the cracks just seemd to be an initial relief of stress and they never became more than the finest hairline.

On a boat still in warranty though I'd try a gentle approach to the dealer but not be amazed if he said it was just cosmetic.

[Doug Stormforce]

I am not saying you want them but hairine cracks are generally not a major problem. It is likely that they are only in the surface and the fibre glass layers underneath are OK.

However if it is in warranty get it back to the dealer and politely tell him you want it fixed.

As said above a few images would probably tell us more.

[Bobalong]

Right, having read a bit more on the forums about this problem, I can give some more information. The hairline cracks are where the knees join the transom. Pictures are as follows: overview of the transom looking aft, with problem areas circled in red; individual photos of the hairline cracks in the problem areas; photo of the cracks on the aft side of the transom; note that these cracks are on both sides, extending under the engine mounts but have yet to meet up in the centre.

Any thoughts/advice welcome!

[Doug Stormforce]

2 of those cracks look more than hairline, get it back to the dealer

[Polwart]

Not looking good. What does the ce plate say about engine weight? Suspect trading standards might be interested in his approach to ce marking from what we've heard.

[Ian M]

Just a thought, as others have said take the rig back but do not hand over that 'updated' manual, copies yes, but hang on to the original. If it gets nasty you may need it.

[biffer]

my guess is, as that is an internal moulding it doesn't fit the external one exactly so it flex's a bit, that bit up round the engine i would think is the joint between them both