bow going too far down- rib plowing

[bbar]

Hi, 2001 nautica ribjet 10. Boat gets on plane but then continues to go too far down so that by 20 mph it is plowing and uncontrollable. Hull is not warped or out of shape. By design, there is alot of weight in the front which I can't do anything about. Tried putting concrete blocks on the swim platform which made a little difference but not enough. Need ideas on what I can do to either the underside of the hull and discharge of the jet nozzle (or both) to keep the nose up. thanks.

[Salty Pete]

Not sure if you have inboard or outboard.
If it is outboard have you tried trimming. The outboard may be down too far pushing the bow into the waves.

By lifting the outboard it pushes the stern down and lifts the bow.

[ShadowDiver]

Originally Posted by bbar

Hi, 2001 nautica ribjet 10. Boat gets on plane but then continues to go too far down so that by 20 mph it is plowing and uncontrollable. Hull is not warped or out of shape. By design, there is alot of weight in the front which I can't do anything about. Tried putting concrete blocks on the swim platform which made a little difference but not enough. Need ideas on what I can do to either the underside of the hull and discharge of the jet nozzle (or both) to keep the nose up. thanks.

Unfortunately, the Ribjet 10 is a badly designed boat. If you look at all of its competitors in the market place you will see the jet pump coming out of the back of the boat.

In the Ribjet 10 the engine, the quite heavy Rotax three-cylinder, has been located a long way forward. In fact, the front of the engine is well into the forward third of the boat. So far forward that you cannot even see the jet pump from behind.

Putting concrete on the rear platform and it having no affect shows how far out the trim of the boat is. I tested one in Fort Lauderdale and was left very unimpressed.

I was solo in the boat, I think that as the boats size and proportions are particularly suited to a large motor yachts garage, the designer has presumed that there would always be a minimum of two onboard and perhaps three, with a member of crew taking the owner and his wife ashore.

[HDAV]

Pump wedge or ride plate shims will do more than concrete but as a tender it may not have been designed to plane really which motor does it use?

@shadowdiver Rotax?

He said it was Yamaha when you posted the same thing in 2019???


https://www.rib.net/forum/f8/nautica...ing-81798.html

[ShadowDiver]

Originally Posted by HDAV

Pump wedge or ride plate shims will do more than concrete but as a tender it may not have been designed to plane really which motor does it use?

@shadowdiver Rotax?

He said it was Yamaha when you posted the same thing in 2019???


https://www.rib.net/forum/f8/nautica...ing-81798.html

The one I tested had a three-cylinder Rotax, as fitted to the Sea Doo Personal Watercraft at that time. So I guess the manufacturer must offer an option of this or the Yamaha PWC engine.

[bbar]

This one is older and uses the late '90"s yamaha jet ski driveline. Yes, it is definately designed too far forward (fuel tank in the nose; motor forward) but I haven't heard of anyone else having this degree of driveability problem. At 20 mph (and not even 1/4 throttle) it is plowing so bad that it is digging in and violently turning trying to toss me off, so I'm assuming it is supposed to go faster than that??? and that mine has something extra bad going on. I have seen a 2 degree up angle pump wedge at riva racing. If that will fit my older pump, it is something I will look at (although I think I need more than 2 degrees. Ii have also been told I could have a hull hook that is forcing the bow down.

[HDAV]

Originally Posted by bbar

This one is older and uses the late '90"s yamaha jet ski driveline. Yes, it is definately designed too far forward (fuel tank in the nose; motor forward) but I haven't heard of anyone else having this degree of driveability problem. At 20 mph (and not even 1/4 throttle) it is plowing so bad that it is digging in and violently turning trying to toss me off, so I'm assuming it is supposed to go faster than that??? and that mine has something extra bad going on. I have seen a 2 degree up angle pump wedge at riva racing. If that will fit my older pump, it is something I will look at (although I think I need more than 2 degrees. Ii have also been told I could have a hull hook that is forcing the bow down.

Ride plate could be the issue photos will help but without seeing the bot impossible to say

[HDAV]

Originally Posted by ShadowDiver

The one I tested had a three-cylinder Rotax, as fitted to the Sea Doo Personal Watercraft at that time. So I guess the manufacturer must offer an option of this or the Yamaha PWC engine.

Interesting not seen one with a 1503 Motor

[bbar]

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[babbot1]

Does this boat have floatation foam in the hull? Could be water logged adding even more weight. Maybe take it to a weight station and see how close you are to the specification.