Sometimes, I miss my trim.

[h2oskierfl95]

I love pretty much everything about my Yamaha. The one thing I really miss, coming from outboards and I/Os is trim. I know they now have it on some of the Waverunner models, but I haven't heard any talk of bringing it to the boats. I feel like that would be one feature that would make me think about upgrading.

 

[Babin Farms]

Put trim tabs on and you’ll be loving the Yamaha 100%?

 

[Cobra Jet Steering LLC]

I put plaining surfaces on my deluxe super magnum and deluxe super ultimate steering systems to provide faster hole shot and a smoother ride in chop and they hover over the water when the boat is on plane to avoid making spray and avoid slowing the boat down . When the bow comes up it puts them in the water so they reduce the bounce and smooth out the ride plus they do not need to be huge due to the leverage they have being positioned further back from the transom than trim tabs.
.

 

[h2oskierfl95]

Put trim tabs on and you’ll be loving the Yamaha 100%?

Yes, trim tabs can work great to keep the nose down, but they can't do anything to raise it up a little in rough water or get a little bit more of the hull out of the water at full throttle to get me a few more miles per hour.

 

[Cobra Jet Steering LLC]

Yes, trim tabs can work great to keep the nose down, but they can't do anything to raise it up a little in rough water or get a little bit more of the hull out of the water at full throttle to get me a few more miles per hour.

Yes that is true and even on the small hulls of jet skies the trim does not do much in comparison to a prop boat because the prop pulls so it pulls the back of the boat down to lift the hull but a jet pushes and it does lift the bow slightly but nothing like a prop.
The plaining surfaces I designed do cut down the bounce in chop and produce a smoother ride in that situation and they get your hull up on plane quicker and if engaging in water sport activities you don't want the hull up in the front . Another thing that my super steering does is allow you to TACK large waves so you can carve them easier and safer.

 

[Bottom Bracket]

The other thing an outdrive will do is let you point the bow high at low speeds.
I don't miss the torque steer backing down. My Cobra fins help with this on my Yamaha.

The go fast river jetboats around here do these or a varation for bow control and top speed.

https://www.placediverter.com/

 

[Cobra Jet Steering LLC]

You could add a pump wedge and angle the pump nozzle end up slightly pump wedge for Yamaha jet pump - Google Search

 

[Cobra Jet Steering LLC]

The other thing an outdrive will do is let you point the bow high at low speeds.
I don't miss the torque steer backing down. My Cobra fins help with this on my Yamaha.

The go fast river jetboats around here do these or a varation for bow control and top speed.

https://www.placediverter.com/

Those nozzles are from 750 to 1100 dollars I am selling my super steering way too low !

 

[gthorson]

Yes, trim tabs can work great to keep the nose down, but they can't do anything to raise it up a little in rough water or get a little bit more of the hull out of the water at full throttle to get me a few more miles per hour.

Here's a little anecdotal field test about getting the hull a little more out of the water. I tried various seating arrangements at full throttle to see what the fastest weight distribution is. I found that the weight in the bow made the boat slower. Keeping the kids in the cockpit gained a couple mph. I've spent some time thinking about this and what I figure is the weight in the bow tipped the hull forward, bow down/jet up. I think what was happening was the intake/suction did better with the stern down. So for a jet the tradeoff to hull out of the water is the propulsion is also out of the water, similar to the breaking point when trimming an outdrive just past the point of optimal. Maybe there is an opportunity for an adjustable ram style pump intake.

 

[Cobra Jet Steering LLC]

Here's a little anecdotal field test about getting the hull a little more out of the water. I tried various seating arrangements at full throttle to see what the fastest weight distribution is. I found that the weight in the bow made the boat slower. Keeping the kids in the cockpit gained a couple mph. I've spent some time thinking about this and what I figure is the weight in the bow tipped the hull forward, bow down/jet up. I think what was happening was the intake/suction did better with the stern down. So for a jet the tradeoff to hull out of the water is the propulsion is also out of the water, similar to the breaking point when trimming an outdrive just past the point of optimal. Maybe there is an opportunity for an adjustable ram style pump intake.

These pumps are out of the water on plane even 1/3rd of the rudder is out of it. That is why I use the nozzles for the plaining surfaces , and why they are hovering over the water on plane

 

[Dave burke]

That’s a great picture Jeff. Now I realize why the water between the wakes is rough when I’m slaloming. I love the pull from the Yamaha but otherwise I prefer skiing behind my old Chaparral stern drive. I can also use the trim to make the wake a little smaller.

 

[Cobra Jet Steering LLC]

That’s a great picture Jeff. Now I realize why the water between the wakes is rough when I’m slaloming. I love the pull from the Yamaha but otherwise I prefer skiing behind my old Chaparral stern drive. I can also use the trim to make the wake a little smaller.

Ok but just think of the huge amount of resistance a lower unit provides as opposed to a jet drive and on a twin jet that has the rudder I add a patented second tie rod to allow you to set your nozzle angles using the tie rods to hold the setting unlike a cable would and the tie rods are UP OUT OF THE WATER ON PLANE ALSO . I have a lot of experience doing this since I began this in 2001 for my own boat and then a ton of Yamaha jet boat owners asked me to fix their boats. So I did. But it is my baby so I specialize in it for over 2 decades now.

 

[gthorson]

These pumps are out of the water on plane even 1/3rd of the rudder is out of it. View attachment 215198 That is why I use the nozzles for the plaining surfaces , and why they are hovering over the water on plane

The outlet is out of the water, the inlet is not. I think getting the stern too high out of the water compromised the intake effectiveness.

 

[Cobra Jet Steering LLC]

The outlet is out of the water, the inlet is not. I think getting the stern too high out of the water compromised the intake effectiveness.

Honestly if that were even a little true you would get instant cavitation if the pump was not getting proper flow of water to it

 

[gthorson]

In this case suction of air, not cavitation, cavitation being the literal separation of the water molecules forming vacuum bubbles. Similar to a PWC that loses suction as it jumps or crosses waves. You can hear it as the engine revs and the PWC slows. I'm suggesting that the layer of water immediately under the boat has more turbulence at the surface than inches further down. The goal of getting the hull out of the water has a limit as you will try to intake the more turbulent water at the surface resulting in loss of speed. I think the same happens when cruising in rough water where the waves introduce more turbulent flow under the boat.

 

[Cobra Jet Steering LLC]

In this case suction of air, not cavitation, cavitation being the literal separation of the water molecules forming vacuum bubbles. Similar to a PWC that loses suction as it jumps or crosses waves. You can hear it as the engine revs and the PWC slows. I'm suggesting that the layer of water immediately under the boat has more turbulence at the surface than inches further down. The goal of getting the hull out of the water has a limit as you will try to intake the more turbulent water at the surface resulting in loss of speed. I think the same happens when cruising in rough water where the waves introduce more turbulent flow under the boat.

Water is not compressible so the only way water would be less dense is if it had air mixed in and I just don't see that based on the position of the hull I have been out in hurricane waves jumping huge waves and tacking them as I went up them at the same time to hit just next to the curl on the top and I can not say I ever had cavitation. So not buying into that supposition at all but it is just my opinion based on many - many years of first hand experience.

 

[Bottom Bracket]

Something like this?

Variable Water Jet Drive | See How It Works | Nozzle

IntelliJet’s variable pitch propeller with variable inlet and variable nozzle means continuous range of forward, neutral and reverse.

www.iijet.com

 

[Cobra Jet Steering LLC]

That is hilarious I build myself very special intake grates top secret ones and I can see this will snag weeds and any thing under the hull creates drag and all jets with a reverse bucket have no gears grinding when you shift and it splits the thrust this is as old as the hills I would not pay any attention to the real useability of that design but that's just my opinion.
Now if you want better distribution of the water as it goes through the intake grate and feeds the pump better get one of these from RIVA it is called a top loader and it puts water on top of the impeller more evenly with the bottom of the impeller.

 

[Cobra Jet Steering LLC]

If I had not designed custom intake grates for my own use I would not even use a jet in the Tampa bay area the weeds are horrid.
I would be stopping every 15 minutes to remove them.
Also the reverse move I came up with 20+ years ago is also a big help for removing weeds from the intake without leaving the drivers seat. Prior to that I always had props and the only prop I had issues with was one on my pontoon boat so I designed a weed deflector for that setup and it worked great. But I also designed big water skies next to and between the pontoons to get the boat up on the water easier and keep the bow from going down on big waves and washing across the floor since everyone liked to ride in the front of the boat .

 

[Eldonfredo]

Wait, custom anti weed intake grates? Did I read that right? Take my money. I’m few weeks away from parking the boat for saragassum season in south Florida.