nose of boat going too far down- boat plowing

[bbar]

Hi, 2001 Nautica rib jet 10. After the boat gets on plane, it continues to go too far down so that by about 20 mph, it is plowing and uncontrollable. The hull is not warped or out of shape. By design, there is alot of weight up front that I can't do anything about. I have tried putting concrete blocks on the swim platform which helped a little, but not enough. Need ideas on what I can do to the bottom of the hull, or the back of the jet nozzle discharge, or both, to keep the nose up.
thanks.

 

[Sotally Tober]

Trim tabs may help.

 

[AZMark]

Trim tabs may help.

You’re joking...

 

[AZMark]

Do you have it inflated properly?

A psi or two could cause that so use a gauge and not just feel.

 

[HangOutdoors]

Man cmon put the trim tabs on the boat

 

[AZMark]

Just saw your earlier posts from a couple years ago. Did you restore that thing and get it running? That’s a rare project. Pictures?

 

[Julian]

Assume there is no way to shim the nozzle so it points up more?

 

[bbar]

Thanks for responses fellas. I will post pics when I get a chance. Yes, put humpty dumpty back together and it floats and runs well but, as mentioned, starts to plow to the point where it will violently catch and turn, almost tossing me off. It's worse with the tubes correctly inflated, and a bit better with them deflated. No way to shim the nozzle that I know of (maybe someone makes a 5 degree up angle nozzle?), but I was thinking of putting some kind of deflector at the back of the nozzle or on the rear of the ride plate to deflect the water up. What make is that one in the picture?

 

[zipper]

And I assume no one is in the boat/ bow when this happens. How does the Yamaha motor run? Are you getting the RPM's you expect? Do you hear/feel any cavitation? What condition are the impellor and wear ring in. We like pictures, the jet pump nozzle, the FRP hull, dings in the impellor, etc.
Would have liked a rib jet, but we bought an 11' Zodiac alum. rib with a 15 hp Merc instead.

 

[AZMark]

Thanks for responses fellas. I will post pics when I get a chance. Yes, put humpty dumpty back together and it floats and runs well but, as mentioned, starts to plow to the point where it will violently catch and turn, almost tossing me off. It's worse with the tubes correctly inflated, and a bit better with them deflated. No way to shim the nozzle that I know of (maybe someone makes a 5 degree up angle nozzle?), but I was thinking of putting some kind of deflector at the back of the nozzle or on the rear of the ride plate to deflect the water up. What make is that one in the picture?

No idea, I had to google what your boat was and that was one of the results.

You’re going to have a hard time with any deflector, you need down force in the back and that’s hard to do. On jet skis people will shim the back of the ride plate or use extended ones to generate more pressure and keep the front end down, but you’ve got the opposite issue.

 

[eastcoaster]

You need to somehow change the angle of the nozzle. Something is out of spec
Trim tabs will not help get the bow up

 

[Sbrown]

Riva racing has angled spacers you can use to adjust the nozzle angle.

 

[Cobra Jet Steering LLC]

Absolutely no trim tabs !!! just would make it a lot worse,,,,,,,,, you probably have what is called a power hook where the center of the hull flexes and creates a cavity that gets worse as you go faster ,get under the hull with it on the trailer and push up on it if it flexes at all you will need to fix it usually it is a bad center stringer that has rotted away. Check the bottom for soft spots close to the transom

 

[zipper]

Hooks can occur if the boat transom hangs over the bunks on a trailer and gets bounced around while towing. They are also built into the hull by some manufacturors for handling at speed. ie. Baja.

 

[Sbrown]

Hooks can occur if the boat transom hangs over the bunks on a trailer and gets bounced around while towing.

View attachment 145783

Something that everybody who moved their winch towers rearward on the trailers to get "optimum" tongue weight, should be looking at very closely, because I'm pretty sure from experience that a bunch of those boats are hanging off the end of the bunks. And it doesn't require a lot of bouncing to have happen. Just letting it sit on the trailer can cause it, aggravated by tight stern hold downs.

 

[Zizzou 192]

nautica rib jet 10- bow too low- boat plowing - RIBnet Forums

Hi, When the boat gets on plane, the nose comes down too far and it is plowing making it very difficult to steer and handle. I'm pretty sure that I can't do anything with the jet pump to compensate

www.rib.net

Everyone on here should be able to figure this one out from that last pic of the reverse bucket hanging over the nozzle.

 

[Cobra Jet Steering LLC]

what picture????

 

[zipper]

nautica rib jet 10- bow too low- boat plowing - RIBnet Forums

Hi, When the boat gets on plane, the nose comes down too far and it is plowing making it very difficult to steer and handle. I'm pretty sure that I can't do anything with the jet pump to compensate

www.rib.net

Everyone on here should be able to figure this one out from that last pic of the reverse bucket hanging over the nozzle.

He said it was not his boat or picture. Although that one does have some issues. A lot of corrosion, zincs?, there is a piece missing from the bucket and I can't tell from the angle but the reverse bucket may be hanging down too far over the nozzle blocking/diverting thrust, if that is open all the way. A picture of his, I asked for in my first post, would be helpful. We can't see what we can't see.

@bbar You have been at this a while now.
@Cobra Jet Steering LLC here is that, not his, picture. From the link.

 

[bbar]

Thanks all for the input. I have attached 3 pictures. I don't know that they will help much but it's all I have till I take some more. First 2 are my boat; 3rd is an 11 ft. with the same pump. Concerning info you guys have provided:

Looked at riva racing and found a 2 degree up angle pump wedge for yamaha pumps.. If it fits my older pump, it may be something to try. I have a feeling I need more than 2 degrees but......

I will check the back of the hull with a long level to see if there is a hook by design.

When I aquired boat, it had been sitting in a dirt parking lot on its hull for about 8 years. I don't think that would have given it a hull hook??? When I got it , I put it on the only trailer I had at the time, and it was sitting off the back of the bunks by about 1 -1 1/2 ft. for several months. Almost no over the road movement, just sitting on it. There is relatively little weight in the back of this thing, but.....

It has now been fully on the trailer for almost a year. If there was a hull hook, will it self correct? (assuming no stringers are broke; if it even has any stringers?)

 

[zipper]

Thanks all for the input. I have attached 3 pictures. I don't know that they will help much but it's all I have till I take some more. First 2 are my boat; 3rd is an 11 ft. with the same pump. Concerning info you guys have provided:

Looked at riva racing and found a 2 degree up angle pump wedge for yamaha pumps.. If it fits my older pump, it may be something to try. I have a feeling I need more than 2 degrees but......

I will check the back of the hull with a long level to see if there is a hook by design.

When I aquired boat, it had been sitting in a dirt parking lot on its hull for about 8 years. I don't think that would have given it a hull hook??? When I got it , I put it on the only trailer I had at the time, and it was sitting off the back of the bunks by about 1 -1 1/2 ft. for several months. Almost no over the road movement, just sitting on it. There is relatively little weight in the back of this thing, but.....

It has now been fully on the trailer for almost a year. If there was a hull hook, will it self correct? (assuming no stringers are broke; if it even has any stringers?)

Thanks, but you are right, they do not help me much. Was wanting to see the pump and reverse bucket alignment. Maybe a pic. of the impellor and wear ring condition. If you have a tachometer, what RPM's are you getting from the motor? You said the boat does get on plane, but what goes down too far, the rpm's as in throttle drop? Or just the bow, maintaining rpm's but losing speed? As in cavitation?