cat with water coming over transom

[tug_tellum]

Re: cat with water coming over transom

Thanks Darren and Robbo
On a mono hull, the cavitation plate is best if it lines up with the bottom of the hull (I think this is correct). Being a Cat there is nothing in the tunnel to go by, so how far down should the motor be. What I am trying to say is, how do I know if the motor is far too low ?
tug_tellum

[scottar]

Re: cat with water coming over transom

Not so much a foil as a splash plate - not the first time I have seen it. Essentially an extended version of what is already there on many outboards but nowhere as large as a foil. Mounts on the plate above the AV plate if there is one. It will only work though if it is above water while the issue is occurring which, without being able to have a good look will be a bit difficult to tell but from the description of the amount of water I don't think it will be. If you want to stick with the cat hull I think the splitter previously mentioned would be the first point of call

[tug_tellum]

Re: cat with water coming over transom

Thanks Scottar. Any idea how big the splitter needs to be (just roughly)?
tug_tellum

[Bremic]

Re: cat with water coming over transom

Thanks Darren and Robbo
On a mono hull, the cavitation plate is best if it lines up with the bottom of the hull (I think this is correct). Being a Cat there is nothing in the tunnel to go by, so how far down should the motor be. What I am trying to say is, how do I know if the motor is far too low ?
tug_tellum

The general rule is that the cav plate should be skimming the water when on the plane. With the motor between the cats sponsons, motor height in relation to bottom of hull will be irrelevant in your case, I should think. If the motor is too deep (Cav plate is buried), the leg will be creating extra drag and the motor will be working harder than necessary.

[tug_tellum]

Re: cat with water coming over transom

The general rule is that the cav plate should be skimming the water when on the plane. With the motor between the cats sponsons, motor height in relation to bottom of hull will be irrelevant in your case, I should think. If the motor is too deep (Cav plate is buried), the leg will be creating extra drag and the motor will be working harder than necessary.

Bremic, the motor doesnt seem to be working too hard as it gets up out of the hole and onto the plane fairly quickly. I have no idea where the cav plate sits when on the plane because from half way up the boat where I sit I cant see over the transom and if I sit at the back then the motor will be a lot further under water. Can I put the motor on 1 side instead of in the middle or will it go round in circles like a one legged duck?
tug_tellum

[scottar]

Re: cat with water coming over transom

Thanks Scottar. Any idea how big the splitter needs to be (just roughly)?
tug_tellum

No sorry. I would try and get a look at a Webster or something similar to give you an idea.

[tug_tellum]

Re: cat with water coming over transom

No sorry. I would try and get a look at a Webster or something similar to give you an idea.

Thanks Scottar, that gives me somewhere to start.
tug_tellum

[Bremic]

Re: cat with water coming over transom

Bremic, the motor doesnt seem to be working too hard as it gets up out of the hole and onto the plane fairly quickly. I have no idea where the cav plate sits when on the plane because from half way up the boat where I sit I cant see over the transom and if I sit at the back then the motor will be a lot further under water. Can I put the motor on 1 side instead of in the middle or will it go round in circles like a one legged duck?
tug_tellum

Somebody used to do a fibreglass cat with a single motor mounted on the end of one sponson only, possibly Markham. No idea how they handled.

Edit : there are a couple on Boatpoint, this one has a photo showing what I presume is the splitter that Scott was referring to.

http://www.boatpoint.com.au/boats-for-sale/private/used/SSE-AD-3132447/1983-Markham-38-WHALER?cr=1&psq=%28%28Make%3DMarkham%26%28%28%28SiloType%3D%5BDemo%20and%20near%20new%20boats%5D%7CSiloType%3D%5BDealer%20new%20boats%5D%29%7CSiloType%3D%5BDealer%20used%20boats%5D%29%7CSiloType%3D%5BPrivate%20used%20boats%5D%29%29%26Service%3D%5BBoatsales%5D%29&pso=0&pss=Premium

[tug_tellum]

Re: cat with water coming over transom

Somebody used to do a fibreglass cat with a single motor mounted on the end of one sponson only, possibly Markham. No idea how they handled.

Edit : there are a couple on Boatpoint, this one has a photo showing what I presume is the splitter that Scott was referring to.

http://www.boatpoint.com.au/boats-fo...=0&pss=Premium

Yeah Bremic thats the splitter I have seen before. It is larger than I remembered. That is on a 12ft Whaler, with engine in the middle. Cant say I have ever seen a cat with a motor on one side. I just wonder how it would handle.
tug_tellum

[scottar]

Re: cat with water coming over transom

On the right size boat it would be ok provided the weight distribution could be accounted for and the design was such that the transom was strong enough in the right spots. Pro net fishers regularly run monohulls with the outboard right over on one side to give them as much room as possible to shoot a net away. The issue you would face in something that is only 10 feet long though would be the weight distribution. She may not swim in circles but the potential to turn turtle would be increased for sure.

[tug_tellum]

Re: cat with water coming over transom

That sure doesnt sound like much fun Scottar. I dont mind swimming for recreation but dont like the idea of doing it to save my life.
I will keep trying to find a solution.
tug_tellum

[robothefisho]

Re: cat with water coming over transom

Single motors on cats are set up more by feel then set rules. Ie when they start to slip. But always above the sponson height. Probably about 2 inches above at least.

[tug_tellum]

Re: cat with water coming over transom

Hey Robo, what do you mean by "slip". When you say 2" above the sponson height , do you mean the cavitation plate should be at least 2" above the sponsons lowest point?
tug_tellum

[robothefisho]

Re: cat with water coming over transom

Hey Robo, what do you mean by "slip". When you say 2" above the sponson height , do you mean the cavitation plate should be at least 2" above the sponsons lowest point?
tug_tellum

Hey mate,
Yes you are spot on. Cav plate a couple inches above the lowest part of the hulls.

Normally set them by ear/feel. As in when they start to ventilate you will hear changes in the motor.

[Fed]

Re: cat with water coming over transom

Take some pictures of the transom with the motor in the down position.