RIB JET 10 PLOWING

[bbar]

Hi, I have a 2001 nautica rib jet 10. When I throttle up, the bow comes up and boat does what it is supposed to do, but as I continue to slowly accelerate and the bow settles back down to plane, it keeps going and starts to plow. I have to keep it at about 20 mph and 3ooo rpm to keep it from "going too far" and becoming undrivable. This occurs with no extra weight up front; just what is supposed to be there. Why would this be happening? thanks.

 

[Ronnie]

Does the jet nozzle have a trim function or is it somehow pivoting downward more as the boat speeds up? Any pics?

 

[bbar]

No trim adjustment of any kind. No pics of my complete set up as boat is in storage, but here are pics of my boats driveline without pump, and 2 boats similar to mine with entire set up.

 

[Cobra Jet Steering LLC]

Power Hook !!!
Hull is weak in the center and bowing at speed usually due to a rotten stringer down the center.

 

[Monepit]

I have the same boat. It doesn’t plow. But Witt run up to 4000 rpm and then pull itself back to 3000. Running 25. Will yours cruise faster than 3000

 

[Cobra Jet Steering LLC]

I have the same boat. It doesn’t plow. But Witt run up to 4000 rpm and then pull itself back to 3000. Running 25. Will yours cruise faster than 3000

possibly fuel starvation could be the vent to the tank is clogged, could be a bad fuel pump replace the original fuel pump with an electric pump I do that on all 2 stroke engines see if that helps , also if you have water in your fuel tank as the boat moves it mixes the water and kills the top speed so add a water separator to the system or let it sit and siphon some fuel from the lowest part of the tank and put it in a clear jar see if water settles, another possibility would be trash in the tank being sucked into the fuel pickup and obstructing the fuel flow Also you could have an exhaust leak in the area where the engine is and it is sucking in exhaust that will also do what you described and explain why it goes faster and then slows down, so try to run with the engine compartment vented and see if that solves the problem. Just reflecting back on my years of experience and what I had to deal with and it may also be stale fuel

 

[Monepit]

I’ve had it for a year now. It has always done this. When I got it I had both carbs rebuilt, new fuel filter and new plugs. I’ve run well over a hundred gallons of gas through it. I replaced the CDI and temp sensor. Tried about everything I can think of. I agree it does sound like starving for fuel. Not sure where else to look. I can’t imagine it’s just underpowered since it pulls like a rocket to 4000 rpm then instantly drops to 3000. Which is about 1/3 throttle. When you push the throttle further it changes sound, like more air coming in but rpm doesn’t change. I’d love to find someone that has one of these to see what they're top speed and rpm is. At 3000 it’s running about 25.

 

[84rzv500r]

Power Hook !!!
Hull is weak in the center and bowing at speed usually due to a rotten stringer down the center.

BTW thats one way that the hull designers keep there monster HP boats speed under control... By putting a little concavity in the plaining area of the hull...

 

[bbar]

I've never had mine above about 3200. I can't. It is so squirrely by then that it tries to throw me off of it. If my speedo is right, I'm doing 24-25 at 3000. I got mine as a basket case missing part of the pump. Someone had put a 760 in it but never hooked it up. Ever since I got it sea worthy, I can't get it to keep the nose up and it plows and skids and becomes undriveable.

I was on a boat design chat room who suggested splash rails up front so I am now attempting to temporarily install some splash rails to see if it helps at all.

If you want to pm me, maybe we can exchange pictures and see if we can fix each others problems. Heading out now, won't be back to this till this evening.

 

[Cobra Jet Steering LLC]

To get the bow up make a pump wedge to change the angle of the nozzle and I also had a chine walk really bad with my new skies so I had to fix that but you always have to check the strength of the center of the hull near the back of the boat because when I had that on an older boat it was very difficult to find the reason and the faster I tried to go the slower it actually went. I had never heard of a hull hook prior to that boat however that was the issue and I even changed to a larger engine prior to learning about a hook only to learn a bigger engine just made it worse. And if it is a weak center stringer nothing you do except fixing the stringer will correct the problem.

 

[Cobra Jet Steering LLC]

I've never had mine above about 3200. I can't. It is so squirrely by then that it tries to throw me off of it. If my speedo is right, I'm doing 24-25 at 3000. I got mine as a basket case missing part of the pump. Someone had put a 760 in it but never hooked it up. Ever since I got it sea worthy, I can't get it to keep the nose up and it plows and skids and becomes undriveable.

I was on a boat design chat room who suggested splash rails up front so I am now attempting to temporarily install some splash rails to see if it helps at all.

If you want to pm me, maybe we can exchange pictures and see if we can fix each others problems. Heading out now, won't be back to this till this evening.

That definitely describes a bad set of stringers flip the boat upside down and walk down the center of the hull , look for the hull giving in when you are on it if it gives in you need to re string it and put in a new floor I add a bunch of swim noodles in there between the stringers for flotation , I avoid foam as it stores water and makes the hull heavier over time but as long as swim noodles are not in the sun they last forever and allow water to go past them to the back of the boat to drain without absorbing any water.