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Author Topic: Pump Trim  (Read 873 times)

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Offline Mokai Dreamin'

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Pump Trim
« on: July 24, 2019, 08:50:19 PM »
One of the new features of the version 2, is a two-piece pump. This gave me an idea to trim the boat. I've seen some higher end Yamaha boats, and boats with Hamilton Jets that have this feature, so I was wondering if it might work on the Mokai.

One of the drawbacks to the new design, is there is now 30+ pounds of additional weight in the engine compartment. I'm not so sure this will be an issue for the lighter weight individuals in the 150 to 160 lb range, but I know there's a lot of forum members who are closer to 200 pounds or more, and this boat is not to handle that kind weight with any kind of decent performance. The stern simply sinks too far into the water, and the more gas you give the engine, the deeper it digs in. It essentially becomes counterproductive.

One of the first things I did was to move my gas tank up in front of the foot rest. This made a significant difference, but  I'm concerned that the pulse gas pump may fail pumping gas 9 feet. Right now it's not an issue, but it was never designed to pump gas that far. It's also a bit of a pain to fill the gas tank, and you have to build a platform to keep the tank level or run out of gas prematurely.  In short, it would be nice to find some alternative method of lowering the bow.

I believe Mokai has already moved the seat forward in this model,  but would need some measurements from another person to confirm. It does seem to me like it's more forward.

Anyway, I'm going to create a CAD file of the shim/wedge, but the linkage will also have to be changed to the nozzle. I told Tom I would post some photos of the linkage for some input/creative ideas on how to connect things once the nozzle is angled down 5 or more.

This is just the beginning of the process. It's going to take a while to produce this, get it installed, etc. So with that said please don't start asking in two days where's the result. As soon as I have some results I will post.
Best,
Troy

Offline CC-Coder

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Re: Pump Trim
« Reply #1 on: July 24, 2019, 11:38:41 PM »
The pump and linkage look to be good quality but hangs out like a stinger. Do you expect any problems with cracks under the pump housing as with my 2010 model? Considering the extra weight of the engine and other points you've mentioned, wondering what other issues might arise as a result of the changes. Guess it will be a (weight) and see.  :)
Thanks for all your detailed posts...appreciate it a lot.
🤦🏼‍♂️ Chuck 🤷🏻‍♂️

Offline riverman

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Re: Pump Trim
« Reply #2 on: July 25, 2019, 12:43:01 AM »
Whatever you do I would be trying to design a pump guard first and foremost ! That thing hanging way off the back is just waiting to be destroyed.

Offline Mokai Dreamin'

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Re: Pump Trim
« Reply #3 on: July 25, 2019, 02:00:18 AM »
The purpose of my post was to talk about a method I was working on to trim the boat. I was going to send Tom some images of the linkage for some ideals, but could not attach them in a personal email, so told him I would post online for him to look at. At the same time I figured I would mention what I was doing in case anyone may have an interest in the future. George (hillbilly) expressed an interest in this already, so again, thought I would share my process in case anyone had an interest.

The vulnerability of the pump I think was pretty much talked about when the original ES-Kape came out years ago, and even before people purchased version 1 for that matter. If you have a big interest in that topic you may do a search. That is after all why Tom developed a pump guard.  Unfortunately it's not a direct bolt on for the new model due to design changes. I suspect when and if Tom gets his hands on the version 2 , he  will design a pump guard ( if possible) for those who want that. If there is a demand and need, I think Tom will rise to the challenge. Of course, no one's pointing a gun to your head and forcing you to buy an ES-Kape, version 1 or 2 if the design doesn't appeal to you.

In my river,  which  has a sand bottom ( glacial silt ),  I'm really not too concerned. I don't run up the rapids with a bunch of rocks , or jump logs, etc.  if I did I would have purchased something else or held out for an older model.

Anyway, this has absolutely nothing to do with the topic of this thread, which was developing a method to help trim the boat.  I suggest to you or anyone else if you want to talk more about the  vulnerability of the pump  on the new design,  you start a new topic. That keeps the information relevant to the topic, and helps others when they do searches in the future to find info related to a specific topic.

Enjoy!
Best,
Troy

Offline Hillbilly

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Re: Pump Trim
« Reply #4 on: July 25, 2019, 09:43:08 AM »
Hey, Troy. 

That's a nice new linkage.  Looks doable to convert to the tilt.  Would likely need Tom's aluminum nozzle for strength

Offline riverman

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Re: Pump Trim
« Reply #5 on: July 25, 2019, 10:42:21 AM »
I guess my point was (without any clarification) lol  I have been an avid jet boat user for 25 years with many different versions and hp. and can tell you trim tabs are only effective for once the boat reaches plane to adjust and fine tune the boats levelness at full speed.  The weight of the boat and its load weight plus amount of hp determine how fast you'll get on step. During the acceleration to plane period the back hull by nature will always pull down well bellow the level limit that is determined  by the previous  factors mentioned.  The trim tabs that many have experimented with will most likely have little to no effect due to the narrow hull design and lack of any serious hp.
However don't let that discourage you from experimenting, these boats need lots of that.           
 

Offline Mokai Dreamin'

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Re: Pump Trim
« Reply #6 on: July 25, 2019, 11:29:45 AM »
Thanks Riverman, that comment was helpful to the discussion. I am already doing the best I can to balance or distribute the weight before trying to apply any effects from the trim of the nozzle. The bow already comes down to some degree with the weight distribution, but I think it could benefit from coming down even more to keep all the propulsion going forward. The lower the tail sinks, the more it shovels water instead of pushes it.

The Achilles' heel of this new design may very well be the weight. Over driving the engine was no doubt helpful, but over driving a lighter weight engine would have been more helpful. I still think one of the best upgrades for this new model may very well be an engine that is 20 pounds lighter, but with additional horsepower and torque. Some kind of a hopped up engine IOW that would have been impractical for Mokai to use due to cost. I'm sure they were looking for an off-the-shelf solution after the Subaru wasn't available anymore.

Anyway, that's yet another topic. Just trying to do the best with what's here for now.
Best,
Troy

Offline happul3

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Re: Pump Trim
« Reply #7 on: July 25, 2019, 04:56:26 PM »
One of the first things I did was to move my gas tank up in front of the foot rest. This made a significant difference, but  I'm concerned that the pulse gas pump may fail pumping gas 9 feet.

The hydraulic resistance is proportional to the length and inversely proportional to the diameter in the 4th power ( ~L/R^4). So, it would take only a relatively minor increase in the ID of the fuel line to compensate for its lengthening. For example, if you triple the length, the ID needs to be increased by 1.3X to keep resistance approximately the same. But you may  want to check first whether the pump is overtaxed at all by whichever length you currently have. Fuel pressure gauge, perhaps?   

Offline Mokai Dreamin'

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Re: Pump Trim
« Reply #8 on: July 25, 2019, 05:07:37 PM »
The hydraulic resistance is proportional to the length and inversely proportional to the diameter in the 4th power ( ~L/R^4). So, it would take only a relatively minor increase in the ID of the fuel line to compensate for its lengthening. For example, if you triple the length, the ID needs to be increased by 1.3X to keep resistance approximately the same. But you may  want to check first whether the pump is overtaxed at all by whichever length you currently have. Fuel pressure gauge, perhaps?   
What a treat it is to have an organic chemist on board! Thanks for that info. You helped me quite a few years ago with a question I had about ethanol, so I remember your profession.
« Last Edit: July 25, 2019, 05:12:21 PM by Mokai Dreamin' »
Best,
Troy

Offline Painlesstom

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Re: Pump Trim
« Reply #9 on: July 25, 2019, 05:28:41 PM »
It would be very easy to make some wedges with the 3D printer. Get me a tracing of the pump flange and I could make up some at different degrees of trim, my contribution to the fun. Need to practice with Fusion anyhow. Wouldn't be hard to make a new steering rod that would allow for some increased angle. Looks like you could just get some thread-all the same size to replace what's there, just bend it to match the new angle. You can always replace the threaded section for the stock one, so no permanent changes. 

Vacuum operated fuel pump isn't going to work any harder with longer lines, see no reason that it would affect longevity. Pump is capable of producing more volume and pressure than the engine needs anyhow, they were designed to work with gravity fed fuel tanks. I've heard of others moving their tank forward in other models, never heard of any problems. Riding mowers use the same fuel pump and draw fuel from the tank over many feet of fuel line. Doubt you'll ever have any problem with it like that. 
Tom

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Offline Mokai Dreamin'

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Re: Pump Trim
« Reply #10 on: July 25, 2019, 05:34:41 PM »
Thanks for the response Tom. I figured you would have a pretty straightforward solution. Just bend the thing eh--lol. yes, I  get you're talking about a completely new piece of all thread, but I guess it could work so long as the length was the same.

And thanks for the info on the fuel pump. It's piece of mind knowing it's not likely to go out on me.
Best,
Troy

Offline Painlesstom

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Re: Pump Trim
« Reply #11 on: July 25, 2019, 05:44:02 PM »
Simplest solution that would allow testing, while be completely reversible. I don't spend any more time and effort on prototyping than necessary to get the result. If it works good I'll step it up and make it pretty, if not I didn't waste a lot of time for nothing. lol
Tom

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