Hurricane 2003 GS170 w/90hp Mercury - transom issue

[ruleofthumb]

I just purchased a gently used 2003 17' Hurricane deck boat w/90hp Mercury 4-stroke, and am at a loss to explain this problem. At most any speed up on plane, water cascades up, thru and around the motor mount, goes over the transom and into the motor well and will actually fill it up. This causes water to flow into the bilge through the boot at the motor control lines. It's just odd. I've tried different trim settings and that helps somewhat but it doesn't stop the waterfall. The motor (original to boat) appears to always have been mounted as it is now. This boat design has a small inset hull cavity, below the transom and in front of the lower motor leg, where the bilge plug resides. Perhaps it is causing turbulence or? Any thoughts? Thank you.

 

[Frank Acampora]

The engine sounds like it is mounted too low on the transom.

When the boat is moving on plane, water impacts the leg and rides up it. Several inches above the anti-ventilation plate (cavitation plate) there is another smaller plate cast into the midleg. The purpose of this plate is to direct impacted and rising water outward to the sides. If the engine is too low on the transom, especially if this smaller plate is at or below the water surface while planing, water will rise above it and it can not do its job. Water will fill the splash well.

The small inset or tunnel ALLOWS you to raise the engine higher Thus you must experiment at what setting you get best performance with least ventilation. Mercs should have several height holes in the transom clamps and hopefully, the mounting bolts are in the top holes, allowing you to raise the engine without drilling more holes in the transom.

 

[ruleofthumb]

Thanks for your reply.
I have the boat in the shop now, (draining out 1 yr old gas and cleaning the fuel lines etc.)
Is there a method I can ask them to try to determine the correct mounting position for this motor?

 

[ruleofthumb]

There are available height adjustment holes in the motor clamp. I'll try raising it up a bit and see if it improves the problem. Thanks again Frank.

 

[H20Rat]

post a picture! Just because it came that way, even from the dealer, doesn't mean it is correct. (hull manufacturers generally don't equip the boat with an outboard, that is up to dealer based on the customer demand.)