Water Splashing up From Motor Well

[Dave Carnell]

A builder in TX built a Simmons Sea-Skiff 20 from the Cape Fear Museum plans that I drew. He called yesterday and reports he has a problem with the prop splashing water up through the well while getting up to speed.

He is using a 70HP Johnson 2-cycle long shaft motor-not unusual for the boat. The cavitation plate is about 2" below the surface at rest.

Simmons used ca. 1½" wide baffles each side of the well, as this boat does. I know little about motors. Does anyone have any ideas of how to solve his problem?

[On Vacation]

Dave he will have to raise the motor for sure. Two inches below the keel is too much. With the angle of the mounting board being only 11 degrees on the plans that I have, and the overall height, the plate is too low. Tell him to raise engine and put staggered strips on top to add to the height of the well and it will almost stop the water. If it has trim on it, start out with it up a little. It will take a little longer to get on plane, but he not get the water in the boat.

[Tom Lathrop]

Dave,

There are at least two sources that could be causing the splash. One is the prop wash that the baffles you speak of are to eliminate. With the prop so low, that is probably not the cause. It is more likely forward and upward splash from the whole lower unit. Raising the engine to the proper height with the anti-ventilation plate even with the bottom of the hull as Oyster said will help. Installing a baffle on the forward side of the lower unit a few inches above the waterline will also help. Just increase the size of the baffle that is usually already there.

[Memphis Mike]

It the lower unit causing the problem.
Same problem I had with my skiff. Raising
the motor eliminated it.

[jeff pierce]

I dunno anything about this stuff, so I won't offer any advice, but I'm wondering if there was a misunderstanding here. Everyone seems to agree that the motor is too low because, as Oyster noted "two inches below the keel is too much" (for the cavitation plate). Seems reasonable to me, except that's not exactly what Dave said. He said 2" below the surface, which I took to mean the water surface not the bottom surface of the hull. Depending on the hull design this could be a big difference.

[Tom Lathrop]

Jeff,

I guess we assumed that no one would mount a motor with the prop hidden behind the transom and expect it to work. Of course, we may be wrong about that. If he actually did that, it should be overreving and making all kinds of fuss.