water coming over stern help

[roaoro]

Sorry if this isn't the right category. I recently bought a 14 foot aluminum boat, and I've noticed at top speeds water comes over the stern. Is there something I can do? It only happens at full throttle, the water seems to be hitting the lower unit on the outboard and coming up over and getting everything wet in the boat. It's only a 15 horse motor and within the specs of the boat. The tilt on the motor also seems to be fine, the boat planes out nice and level.

 

[26aftcab454]

Re: water coming over stern help

You my have to lower or raise the engine height. The cavitation plate ( horizontal fin above the prop) should be slighly below bottom of boat. Hopefuly someone with a simular set up can chime in. Good luck!
And Welcome to iboats!

 

[sublauxation]

Re: water coming over stern help

If you have a transducer on back that can cause water to come over the transom as well.

 

[Texasmark]

Re: water coming over stern help

On the leading edge of the lower unit is a deflector plate that protrudes out forward of the leading edge. The purpose of this deflector is to prevent such as you mentioned. If the plate is below the water line it is useless and at WOT you can have enough water force pushing against the leading edge of the LU to force water up and into the boat.

So, Check your engine height. If you have a 20" mid section on a 15" transom it will cause the problem.

On the transducer, if you can't determine it to be the problem, remove it and see if the water stops. If mounted too low it could cause the problem as mentioned.

Mark

 

[roaoro]

Re: water coming over stern help

Thanks for the replys. I suspected the motor may be setting a bit low. It is a 98 nissan 15hp short shaft. The transom does measure 15", and the cavitation plate seems to set 2-2.5" below transom. I'll need to explore some options for raising the motor an inch or two. I don't see any obvious adjustments on the motor. I'll post on the Nissan forum to get some more info.

 

[Willyclay]

Re: water coming over stern help

I do better with pictures and the link below has some info in diagram form that I think is very helpful.

Outboard Motor Shaft Length

If your motor has a clamp-on transom bracket without any bolts through the transom, then you should be able to insert wooden shims between the top of the transom and the motor to raise the mounting height. Worse case, you will have to buy/build a jack plate. Good luck!