Possible to install trim system?

[Flaustin1]

I have a homebuilt fiberglass boat with a 717 in it. I was wondering if its possible to install a trim system on the boat.

When running at about half throttle, the boat rides good with the nose up just where it needs to be. When you go from half throttle to full throttle, the nose of the boat is pushed down.

This makes me think the angle the ski bottom was glassed in at is slightly off. If I had a trim system, I think I could get probably another 10mph out of it. I don't know what year/model ski the hull motor and pump came out of but im assuming its mid 90's.

Anybody ever done anything like this? Any help or input would be appreciated.

 

[SabrToothSqrl]

have any pics?

I'm thinking you could put a trim nozzle on and either just 'set' it at a trim level, or add manual trim if you wanted... power would be overkill I'm thinking.


I don't know what part # you'd need, but I'd go on ebay and get one used, or check out MiniTonka (I know I didn't spell that right, sorry)

He's got a ton of used parts.

thats the first piece you'd need. I'd play with just bolting up a adjustable length piece (stainless) on the nozzle.

of course, if you have reverse you've just complicated the whole thing, as only the RX had trim AND reverse on one setup...

 

[Spimothy Leary]

there's no reason it can't be done, and i'd assume it'b been done, although you'd have to do some creative work.
1) you'd need a nozzle setup that allows trim. (many many out there)
2) you'd need to do a thru hull setup to run the cable
3) you'd need either a manual or electronic control lever or button)

the only thing that will limit you is your creativity, and ability.

i'm sure more will chime in, but I see absolutely no reason it couldn't be done relatively inexpensively.

 

[LouDoo]

I would think the setup like off of a 95XP would work. Nick would probably be the best person to ask. [MENTION=41828]Minnetonka4me[/MENTION]

Lou

 

[Spimothy Leary]

I might have a set of 140 nozzles with trim stashed up in my attic, i'll take a peek tonight, I've been slowly cleaning out the crates in my garage, the attic is next !

 

[Krispy]

I am sure all of us want to see pictures of this thing so post them up! We will be able to identify the pump setup and what parts to go with it.

If you have a 140mm pump this pump setup would work and allow you to adjust the trim till you found the sweet spot for your ski.

Not my part and I can't vouch for the seller. [MENTION=41828]Minnetonka4me[/MENTION] will be able to steer you in the right direction (bad pun?)

 

[Spimothy Leary]

I am sure all of us want to see pictures of this thing so post them up! We will be able to identify the pump setup and what parts to go with it.

If you have a 140mm pump this pump setup would work and allow you to adjust the trim till you found the sweet spot for your ski.

Not my part and I can't vouch for the seller. [MENTION=41828]Minnetonka4me[/MENTION] will be able to steer you in the right direction (bad pun?)

I thought about that myself that's the hx manual trim, but it would then pretty much leave him stuck in 1 trim position w/o hanging over the back to adjust it, I thought (maybe incorrectly) he wanted to be able to trim it up/down depending on speed.

 

[Flaustin1]

Jet boat

heres a pic. I will get some pics of the pump, motor, hull setup Friday. Its currently at my bro in laws in his barn. Weve got a big storm coming through tonight and I just painted it.

 

[Flaustin1]

Yes it does have reverse but I don't use it and the dang cable is in the way so I could do away with it if necessary. Id like to have power trim to have better control over the boat. Its heavier than a ski so id assume the trim would need to be all the way down to plane the boat off. Id like to be able to adjust the trim depending on speed im running.

 

[Minnetonka4me]

Yeah the only way to have both reverse and trim is a 951 155mm pump, they never did it on a 140.

 

[SabrToothSqrl]

I'd like something like this to run in crazy shallow water. Some thing with a metal hull.

 

[Sportster-2001-951C-Stock]

A boat with too much rocker will tend to porpoise, could be your hull may have some amount of hook in the bottom?

Looking at that photo it seems like there's some "V" to the hull, so it should turn fairly well as opposed to just sliding sideways.

 

[Sportster-2001-951C-Stock]

Might be able to place a wedge on the fixed nozzle to change out outlet angle. Upward I suppose maybe, but a hook is going to just slow the boat down (the usual complaint) that's probably b/c of a suction that occurs pulling the hull down into the water?

What happens if you place the passenger weight further back toward the transom, does it help at all?

Another possibility that might help since you seem to have some "V" might be attaching lifting strakes if there aren't any or they are small, to help lift the bottom up. They have to be in the right place of course hard to say where exactly would be the best location, would have to research that idea a bit.

Here's an article on the subject, perhaps this can help explain a little about the idea:

http://www.sponbergyachtdesign.com/Bluebill.htm

 

[Krispy]

A boat with too much rocker will tend to porpoise, could be your hull may have some amount of hook in the bottom?

Looking at that photo it seems like there's some "V" to the hull, so it should turn fairly well as opposed to just sliding sideways.

You are talking about many things I have never heard before...Care to explain the concept of rocker and hook for the good of the thread? I find this stuff extremely interesting.

Might be able to place a wedge on the fixed nozzle to change out outlet angle. Upward I suppose maybe, but a hook is going to just slow the boat down (the usual complaint) that's probably b/c of a suction that occurs pulling the hull down into the water?

What happens if you place the passenger weight further back toward the transom, does it help at all?

Another possibility that might help since you seem to have some "V" might be attaching lifting strakes if there aren't any or they are small, to help lift the bottom up. They have to be in the right place of course hard to say where exactly would be the best location, would have to research that idea a bit.

Here's an article on the subject, perhaps this can help explain a little about the idea:

http://www.sponbergyachtdesign.com/Bluebill.htm

I will take a look at that link for my own education.

I like the idea of shimming the pump as a way to pick a good "fixed" trim position for a new application. *Deleted end of post, thought about the pump wedge further..

 

[Sportster-2001-951C-Stock]

You are talking about many things I have never heard before...Care to explain the concept of rocker and hook for the good of the thread? I find this stuff extremely interesting.



I will take a look at that link for my own education.

I like the idea of shimming the pump as a way to pick a good "fixed" trim position for a new application. *Deleted end of post, thought about the pump wedge further..

Yes, Rocker and hook refer to the basic shape of the keel from front to back, usually not a factory production issue but it can be.

Most often a hook can form on a trailered boat just ahead of the transom due to weight of the stern not being properly supported by the trailer bunks, the weight needs to be supported at the transom bulkhead by the bunks beneath and if the bunks are not supporting the transom but further forward by several inches or more, the weight of the vessel can cause the surface just ahead of the transom to change into a downward hook as the transom sags downward over time (the keel ahead of the transom is pushed upward).

The trailer bunks must support both the stringers and transom in order to minimize hull shape change over time, so if your bunks aren't in the correct location then move them toward or away from the centerline of the keel to support the stringers, or move the boat forward on the trailer to locate the transom over the end of the bunks so the bunks support the weight at the transom. Ideally, the rear bunker trailer mounting bracket is directly beneath the transom bulkhead and the front bunker mounting bracket is directly beneath the helm bulkhead for maximum support.

Rocker refers to the rounded shape of the keel from front to back like a rocking chair has, this shape helps to improve the hull maneuverability and turning but too much rocker can lead to a porpoising action at planing speeds. Keel rocker is designed into the hull and difficult to change, although misbehavior can be compensated by extending trim plates off the transom, trimming the drive line angle, or shifting weight aftward.

The "V" shape improves ability to move through chop without knocking out your fillings and suggests the presence of rocker, a flat-bottomed jet boat tends to slide sideways in turns due to lack of "V" with rocker, thus adding a scag several feet forward of the transom in this case will improve maneuverability and cross-wind directional stability. Many shallow "V" hulls and flat-bottoms must be fitted with a keel scag in order to make them turn reasonably.

By installing a wedge in the nozzle base (assuming this option is not eliminated by the pump construction), at the location where the nozzle bolts to the pump housing, the outlet angle of the jet pump can be changed without changing the angle of the impeller shaft. Remove nozzle and install a wedge, then reinstall the nozzle. Easy and cheap method for trimming driveline thrust angle.

 

[Krispy]

Yes, Rocker and hook refer to the basic shape of the keel from front to back, usually not a factory production issue but it can be.

Most often a hook can form on a trailered boat just ahead of the transom due to weight of the stern not being properly supported by the trailer bunks, the weight needs to be supported at the transom bulkhead by the bunks beneath and if the bunks are not supporting the transom but further forward by several inches or more, the weight of the vessel can cause the surface just ahead of the transom to change into a downward hook as the transom sags downward over time (the keel ahead of the transom is pushed upward).

The trailer bunks must support both the stringers and transom in order to minimize hull shape change over time, so if your bunks aren't in the correct location then move them toward or away from the centerline of the keel to support the stringers, or move the boat forward on the trailer to locate the transom over the end of the bunks so the bunks support the weight at the transom. Ideally, the rear bunker trailer mounting bracket is directly beneath the transom bulkhead and the front bunker mounting bracket is directly beneath the helm bulkhead for maximum support.

Rocker refers to the rounded shape of the keel from front to back like a rocking chair has, this shape helps to improve the hull maneuverability and turning but too much rocker can lead to a porpoising action at planing speeds. Keel rocker is designed into the hull and difficult to change, although misbehavior can be compensated by extending trim plates off the transom, trimming the drive line angle, or shifting weight aftward.

The "V" shape improves ability to move through chop without knocking out your fillings and suggests the presence of rocker, a flat-bottomed jet boat tends to slide sideways in turns due to lack of "V" with rocker, thus adding a scag several feet forward of the transom in this case will improve maneuverability and cross-wind directional stability. Many shallow "V" hulls and flat-bottoms must be fitted with a keel scag in order to make them turn reasonably.

By installing a wedge in the nozzle base (assuming this option is not eliminated by the pump construction), at the location where the nozzle bolts to the pump housing, the outlet angle of the jet pump can be changed without changing the angle of the impeller shaft. Remove nozzle and install a wedge, then reinstall the nozzle. Easy and cheap method for trimming driveline thrust angle.

If a +1 has ever been deserved surely this is it. Thanks for the explanation.