Avon Rover 3.4 taking in water.....

[MartinG]

Hi everyone, I'm new to the site. Great reading so far, it's going to be many hours of discovery catching up!
But I have an issue for you.
When I'm on the plane there is a flow of water into the rib from the gaps at the corners of the transom as shown in the photos.
I have a Yamaha 25hp two stroke twin fitted, the maximum plated.
Stationary, the rib is watertight, but fills up quickly on the move. I have to bale out a couple of times a day and always arrive back with a few inches of water at the rear.
I can clearly see a flow from the gaps shown in the photo.
I've filled the rib with water and eliminated everything else.
Is this a known fault?

[Fenlander]

I'm guessing your Avon is as made and there are no bits of material missing? Assuming so Avon can't have expected constant splash in that area so I'd assume it is your outboard causing this. It's a very familiar situation for us Aerotec owners where depending on outboard make/model and load carried/boat trim water hits the front of the OB leg and bounces back towards the transom.

On the Aerotec this is at its worse when the OB leg is too deep in the water and most of us find we need a packer on the transom under the OB saddle to raise it 25mm-30mm.

Your OB is quite heavy for a 3.4m so may be pulling the transom down more than ideal. Also how about the positioning of your fuel tank and any other gear? Plus consider the fore/aft positioning of the console?

It may be that altering the trim of how your boat runs and/or a transom packer could be the answer.

The other thing that comes to mind... could you try getting some material glued in place to cover those holes... or is it coming over the transom top too?

[MartinG]

Thanks for replying.
I don't really keep anything much at the rear as I have plenty of starage further forward. I've adjusted the trim of the rib for max speed with one person, and I don't think that's an issue
The Rib is within manufacturers plated limit, maybe well inside as this motor is two stroke and quite a compact unit compared to others, particularly four strokes.
The problem really is that there is considerable wash around the exterior transom. This is finding it's way through those gaps at a rate of knots :-)
I have those plastic vane thingies on the leg, which I believe helps with trim at speed.
I've tried stuffing socks into the gaps, but there is flexing and they fall out :-)
A mate had suggested a product to fill the gap but I need to find out if anyone has had this problem and solved it.
I've mailed an Avon distributor, but without much expectation as I believe they have ceased trading? Maybe because of water logged ribs!! :-)

[Fenlander]

>>>there is considerable wash around the exterior transom

In general the Avon's hard hull should produce a cleaner wash than most of our problematic SIBs so you really need to look at what is creating the splash back. Is it possible to take a lightish person out to look/film over the transom or could you borrow a GoPro and set it up to watch the wash?

Otherwise first I'd try a trip without the OB fins to see if that changes things.... then look hard at the prop/cav plate position relative to the lowest point of the hull to see if there is scope for raising the OB.

I've noticed two different transom shapes on the 3.4 Rovers... one level across the top and the other with a fair rise to where the OB mounts. I wonder which yours is and is the OB the correct shaft length for certain?

[MartinG]

Thanks, gonna work on what you've said and get back to you.
If I could only seal those gaps though, I'm sure that would solve it

[jeffstevens763@g]

second picture is that the bottom of the engine clamp 2/3rds down

[HDAV]

we have a rover 3.40 and from memory i('m not near it now) its the same round the transom, dont recall having water come through the gap so suggest it may be the trim on the motor is your a power trim?

[MartinG]

Not power trim, but easy enought to adjust. I have it set perfectly for an easy and not too high at the front plane and max speed (24mph)
I'm going to try taking the wings off and looking at raising the OB.
But I think filling those two gaps is going to be crucial. A friend has suggested using polymorph. I thought make the plugs with that and then sikaflex in place?

[MartinG]

Originally Posted by Fenlander

>>>there is considerable wash around the exterior transom

In general the Avon's hard hull should produce a cleaner wash than most of our problematic SIBs so you really need to look at what is creating the splash back. Is it possible to take a lightish person out to look/film over the transom or could you borrow a GoPro and set it up to watch the wash?

Otherwise first I'd try a trip without the OB fins to see if that changes things.... then look hard at the prop/cav plate position relative to the lowest point of the hull to see if there is scope for raising the OB.

I've noticed two different transom shapes on the 3.4 Rovers... one level across the top and the other with a fair rise to where the OB mounts. I wonder which yours is and is the OB the correct shaft length for certain?

Theres a raised section on this transom, I can't really lift the outboard anymore I don't think...

[MartinG]

Wish I had cleaned it all before all these photos..... :-)

[HDAV]

I just wish I had photos

[MartinG]

Originally Posted by jeffstevens763@g

second picture is that the bottom of the engine clamp 2/3rds down

New pics below...

[jeffstevens763@g]

Originally Posted by MartinG

New pics below...

No pics

[MartinG]

Originally Posted by jeffstevens763@g

No pics

Sorry, above!!!!!!

[MartinG]

Originally Posted by MartinG

Sorry, above!!!!!!

Still trying to get used to the forum software!

[jeffstevens763@g]

Personally I would loose the dolfin you should be getting 22-24 knots I would think without it depending on prop of course and rpm I would say it's throwing water forward ( never did like them) but I don't like the gap on the tube to transom at all but it looks like a factory build though. engine height looks ok. As far as I can tell
I see two drain plugs on the stern one for the deck one for the keel is that drained ?

[MartinG]

Originally Posted by jeffstevens763@g

Personally I would loose the dolfin you should be getting 22-24 knots I would think without it depending on prop of course and rpm I would say it's throwing water forward ( never did like them) but I don't like the gap on the tube to transom at all but it looks like a factory build though. engine height looks ok. As far as I can tell
I see two drain plugs on the stern one for the deck one for the keel is that drained ?

Thanks, I'm certainly going to try without the fins. They were on when I got it and I've assumed they had benefits.
The rib does 24mph exactly on flat water with a 9 7/8 x 10 1/2 F aluminium prop. I have no idea of the revs as I have no tacho. I would like to try a slightly higher pitch prop but at around £100 just to trial it can wait.
I wonder if the fins slow it a little?
I drain the keel each time I get back, it is always full. I've assumed that's normal. It doesn't affect the speed at all and may help stability?

[Fenlander]

Fins are a marmite thing with folks on here. In truth they are really only ever needed to try and resolve a poor setup. Yes they cause drag and in my experience they can make handling odd.

They have come already fitted to two used outfits we've bought (one SIB and one hard hull) and in both cases the overall performance/handling was improved when they were removed!

[MartinG]

Originally Posted by Fenlander

Fins are a marmite thing with folks on here. In truth they are really only ever needed to try and resolve a poor setup. Yes they cause drag and in my experience they can make handling odd.

They have come already fitted to two used outfits we've bought and in both cases the overall performance/handling was improved when they were removed!

Thank you, can't wait to get out and try finless! A friend said his sib was faster without the fins but I discounted him because he has no gps to measure his speed!

[jeffstevens763@g]

basically the fins are to create lift to get over the bow wave when as fenlander says a poor set up of too heavy a load, drag is created by the lift for obvious reasons.
you say you get water in the keel is it a flooding hull then?,
if not you will have a problem somewhere that water underway will move to the stern when you power up making it dig in, it will then slosh about causing all kinds of stability/ trim problems because it cannot empty that added weight will slow you down too.
so you're getting around 20 knots out of her, in comparison my SIB running a 10 1/4 x 12 on a 25 4 stroke is achieving 22 knots at 5250 rpm. your two stroke with the rib hull should be at least 2 knots faster IMO.
my rig with me in it about 300 kg [43 litres of fuel] for info.
i would buy a tiny tach equivalent about £20 to start try it with the fin & without and go from there.
just to add when you filled the boat with water did you have the keel bung out to see if it seeps through the deck