2001 Islandia Rpm and speed issues

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Ok so I bought 2001 Islandia this summer. During the water test, the engine seemed to have an awful lot of shake, but it seemed to run fine. We topped it out between 40-45 mph on smooth water with three adults on board.

I got it home, and with similar conditions and only two adults, the best I could do was just over 35. Since then it's remained like that until tonight. With me, my wife, and it our give year old boy, I couldn't beach 30mph on absolute glass water.

The only other abnormal thing I noticed, was that a couple times since I've had it, I would start moving the throttle up and the rpms would start shooting over 6k but the boat wasn't accelerating. After slowing down and doing the reverse maneuver I saw recommended for weed removal (putting the boat in reverse, giving some throttle and steering side to side in hopes that the turbulence of reverse would free up any weed can stuck in the intake grate), I put the boat back in forward and gave throttle again. This time, rpms seemed more normal and the boat accelerated and got on plane. Engine seemed to smooth out, but at wot it wouldn't pass 30mph.

I'm new to the jet drive thing, but I've owned and driven often several I/O powered boats. Could this just be a case of weed buildup in the intake? Or something else?

Sorry if this question seems stupid, but I don't know where to begin. I don't need the boat to fly, I didn't buy it for that. I know it should do more than 30mph with two adults, though. Takes an awful long time to cross my lake at 28-30 when trying to get home at night.

Maybe I should mention, engine seems to be running at 52-5500 rpm at wot while doing 28-30mph. Also, I was told the boat say quite a lot at the marina that sold it to me. The previous owner took it out rarely for the last 7-8 years, and at some point recently let it sit in storage for two years.

It fires right up everytime, seems to be smooth when running "fast" but just wont get to speed.

If it's something simple I'm just too dumb to think to check, be sure to let me know, lol.
Everything you describe is cavatation. you have to properly check your pump. Sure, weeds can get in the grate... and depending on what grate you have... it may or may not clear. Putting it in reverse hardly ever helps since it's still sucking into the grate. Shutting off the engine, and rocking the boat can help... SOMETIMES. (especially if it's a shopping bag, or old plastic cup)

From my end of the keyboard... I'm guessing you sucked up a chunk of rope, and its wrapped around the shaft. OR... you have a hunk of something stuck in the impeller blades. I remember once... I got a nugget of wood stuck between the blades. (Size of a ping-pong ball) The boat wouldn't go faster than 5 mph, and shook violently when I tried to go past 2000 rpm. I couldn't even see it until I got under the boat with a flashlight.
Suppose I'll have to yoink the boat out tomorrow then, and have a look I'm there. No experience with jet drives, and honestly I was hoping for that answer. The lake I boat on is known to be very weedy and generally dirty, but I wasn't sure how a jet drive feels when it sucks stuff up. Certainly different than a prop!

I'll check that out as soon as I can. I thought it was worth asking to see if I should be concerned further than that.. but I guess if that isn't the case I'll be back.

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