water over the transom

[Mike in Tac]

I've got a 15hp Merc tiller on my 14' Livingston. In order to try and keep things as balanced as possible, I have moved my fuel can, battery, etc. all up towards the front of the boat. When I have a passenger, they sit on a bench in the middle of the boat. I have found that I can throttle up about half-way or three-quarters without a problem, but when I really rev up water starts splashing up over the transom and into the boat. I have the motor positioned flat against the transom. Does anyone have any suggestions for how I can eliminate this problem?

Thanks a lot,
MIT

 

[Sea Rider]

You need to shim the engine up till water splashes dissapears to achieve this same example which is the sweet engine/transom height for Merc, Tohatsu, Nissan engines.

https://www.youtube.com/watch?v=oBeZjaA76VM

Happy Boating

 

[steelespike]

Normally you would have the motor perpendicular to the water.
I'm thinking you you have a long shaft motor on a short shaft transom.
The anti vent plate (just above the prop) should be about even with the bottom of the transom,
motor trimmed out perpendicular to the water.

 

[Mike in Tac]

Thanks for the tips - MIT

 

[Sea Rider]

Assume you have a short shaft engine on a short shaft 15-15.5" transom, right ? if so, Merc, Tohatsu, Nissan OB's are bit longer than short shafts Yam, Suzy. If with splash over transom water flow is hitting the upper side of the small water deflector plate where the splash is produced, worst at speed. The posted example had same problem, shimming solved the splash issue.

And no, the AV plate even with boat's bottom doesn't match at all as factory specs are 30 to 50 mm from bottom to AC plate. Shimming and testing till best engine/transom height is dialed is the way to go.

Happy Boating

 

[ondarvr]

Livingstons are small catamarans, so getting the engine positioned correctly can be a little different. There is a small keel that breaks the water for the motor, you will need to raise and lower the motor to find the best height. At certain speeds the wake from each hull can meet under the hull and do weird things.

 

[Sea Rider]

Mike, post a rear pic of your combo to check what Ondarvr mentioned. Just currious on that boat's shape. Are those same as the catamarans used to follow rowers, rowing training lessons ?

Happy Boating

 

[Mike in Tac]

No Title

Here are a couple of pics. Looks to me like the deflector plate lines up ok with the bottom of the boat, but there is a lot much room between the hulls for water to come through and make a mess of things. Is that the likely culprit? As far as raising the motor up higher on the transom goes, I've only got about an inch to play with. What do you think?

Thanks, MIT

 

[Sea Rider]

Mike,

It's the same version of a training rowing boat with middle keel, the only difference is that the toons on this type of boat are more separated from middle keel and less wider than yours. Had to cure our Club's training toon, had same issue. You need to dial water flow at speed to pass slightly under upper water deflector plate, provided that boat has engine sitting at 90? on transom and weight is evenly distributed throughout the entire deck for a nice boat ballance.Tomarrow will post one of you picks to show where you need to dial best engine/transom height,

Your's is a rebadged Tohatsu model and these nice engines are natural born splashers if not correctly height seated on transom. Sory best height is dialed only under trial & error, it's not about asking at the forums, it's all about real world practice.

Happy Boating

 

[steelespike]

Try raising it that inch or so.Use a stick to hold it up till you tighten the clamps.

 

[Mike in Tac]

Thanks - the next time I get in the water (maybe in a week or so), I will raise it an inch and see what happens. For what it's worth, I noticed yesterday that when I put the boat in the water the top deflector plate was about an inch under water. I imagine that it was more than that once I piled in!

 

[Sea Rider]

Mike,

Having a long shaft engine with rounded middle leg section water flow could splash at speed over or outer transom.

Your issue is water flow is hitting at around (1) when flow (2) should be skimming right under (3) shim engine accordingly till this sweet engine/transom height is dialed in provided that engine sits at 90? on transom and deck weight is evenly balanced with combo riding on flat calm no wind water cond.



For that to happen will need to know visually at which lower leg height is water flow passing by so to shim height right, could pull you head sideways out transom, have a second boat follow you next to your transom, use a go-pro camera installed on transom facing downwards, you decide.


Happy Boating

 

[Mike in Tac]

Thanks again Sea RIder- the go pro is a great idea! I'll hook it up the next time I get out. MIT