Q - Help with water over the transom

[Adamhorsman]

Greetings. I have a Bombard C5 (4.8m), with a 2001 Mercury 50hp two-stroke. At full throttle there is a "waterfall" of water coming over the transom, just below the steering unit into the boat. This is a substantial amount of water. To help alleviate the problem, I trim the motor up, but if I hit a large wave the engine revs and there is a large loss in power. (I assume the prop has cavitated, as the problem is corrected if I slow down, and/or trim the motor back down)

This afternoon I raised the motor one hole hoping this would correct the problem, but it didn't.

Any help would be appreciated.

Thank you.

Adam Horsman

[Phil Davies]

That's an interesting coincidence - my brother's got a Bombard Aerodeck 3.8m with a 25hp Yamaha 2-stroke, the maximum size engine for this boat, and he has exactly the same problem at full throttle. As yet his dealer has been unable to effect a solution (sounds familiar ).

[Kernow Buoy]

Hi Adam,
My last boat was a C5 and I had that same problem, I found that putting your least favourite child right in the bow does help a little although the screams are a little intrusive! ( This is British sense of humour - honest!!)
But seriously weight forrard does help, additionally I also had hydrofoils fitted to the outboard and again found an improvement with the waterfall situation.
Hope this helps.
Jeff

[Adamhorsman]

Thank you for the responses. Prior to this outboard I had a newer Tohatsu 40hp, which I had no problems with at all. (water, or mechanically) I almost wonder if I need to bump back down to a lighter/smaller outboard. According to Bombard, the boat is rated for up to a 60hp outboard.

As to the weight in the bow, I had two sets of double steel scuba tanks, plus decompression bottles, and other miscellaneous gear. I would venture to say this is at least comparable to one small child, possibly even two.

Adam

[Matt]

With the engine trimmed 'normally', where is the cavitation plate in relation to the bottom of the boat?

[Adamhorsman]

The cavitation plate is ~3-4 inches below the bottom of the boat. (trimmed normally)

Adam

[Wayne Rogers]

I think you'll find that is to low,it should be level with bottom of the hull or higher.If you raise it you will improve top end speed and may correct your problem.

[Matt]

I agree.

Originally Posted by Wayne Rogers

I think you'll find that is to low,it should be level with bottom of the hull or higher.If you raise it you will improve top end speed and may correct your problem.

[Adamhorsman]

Thank you very much. I appreciate all of the responses.

Adam Horsman