Jet don't fit!!

[axelkloehn]

:eek::eek::eek:

Well, here goes the dream of a jet-powered GT21...

I took some measurements yesterday and found out, that the Jacuzzi has a length from transom to coupler at about 20", the Olds engine with belts is about 32" which means overall 52".

What if the engine-room of the GT just has 50" from transom to fueltank/rear cabin wall??

It tells me it does not fit!!!!

This is something which could have been found out before if I were smart enough to take some measures before buying the stuff :boggled::boggled::boggled:

Well, don't give up, Axel- drink some beers and start getting the olds together with the Bravo One- figure something out with the bellhousing/coupler, buy a seawaterpump and a standard waterpump and go on... at least it's no jigsaw-cutouts anymore...

That's about it with bad news from good ol'germany.

Cheers, Axel :germany:

[CaribouLou]

I like the Bravo idea better my self.....

[The Hedgehog]

I was actually getting used to the idea until I saw that boat with two jets. I dunno if I could have less than that.

The bravo will prover to be the most reasonable option in the end. Good luck.

[h2ojerm]

What about setting the jet pump back a few inches?
They do it all the time on racing jet boats.

[Carl C]

I like the Bravo plan better too. Jets can be fast but it seems to take a lot of money and work to get there. Have some good German beer and git it done.

[axelkloehn]

What about setting the jet pump back a few inches?
They do it all the time on racing jet boats.

Thought about this, must be about 10" to have enough maintainance clearance for the front of the engine- but the bottom inlet moves too far backwards than and will be outside the hull. Has to be covered by an extra channel and I don't think this will be very stabil....

[mrfixxall]

shorten the coupler,you dont need a driveshaft! :)
Basicly you need to remove the center part,the plate that bolts to the flyewheel,ujoint's and the splined end ..finished..
the end result will look like this..

[BUIZILLA]

took the words right out of my mouth... :cool:

[Carl C]

shorten the coupler,you dont need a driveshaft! :)

Basicly you need to remove the center part,the plate that bolts to the flyewheel,ujoint and the splined end ..finished..

Cool. How do you know so much??:eek:

OT, Buizilla, shame about the other thread. I was learning stuff like maybe how Merc gets 525 hp with 8.75 SCR. No replies please on that. No hi-jack.

Axel, it sounds like you may get your jet boat after all!

[mrfixxall]

Well lets just say io's are not the only boats i work on,..

this is where i boat!

http://www.youtube.com/watch?v=_qP-EX7YHUA

[Morgan's Cloud]

Not going OT here, I can imagine the fun that a jet powered 18 or 16 could be , but because of the size difference with the GT21 and the some what different perspective that gives you in terms of the 'total boating experience' that would come with it , would not the jet drive be a little annoying after a while where "you're either on a plane jammin' " or you're doing 10MPH , mushing along at 2500 RPM ... ?

In other words , you're either going fast , or you're not going at all .....

[axelkloehn]

shorten the coupler,you dont need a driveshaft! :)
Basicly you need to remove the center part,the plate that bolts to the flyewheel,ujoint's and the splined end ..finished..
the end result will look like this..

Oh Mr. Fixx, I was checking the technical drawing for hours to find the way to shorten the Jet or the coupler, couldn't find any way to gain at least 10" needed for proper installation. I thought about making the double cardan joint a single one or lining up with no cardan at all.
Your idea is very good but might not work on my jacuzzi (see pic). Hmmmh, or may be I did not understand exactly what you mean...

Another question: do ya guys think the GT because of its weight will go 65-70 mph with the Olds/jacuzzi package? That is what I am aiming for without having a short lived engine....

[Donziweasel]

Another question: do ya guys think the GT because of its weight will go 65-70 mph with the Olds/jacuzzi package? That is what I am aiming for without having a short lived engine....

No, not unless you have HUGE power. I read about your inquiry about the efficiency of jets on the other thread. They lose about 25-30% of prop hp over a regular stern drive. Plus, you are dealing with 1970's technology, whihc is probably even less effecient than todays jets.

I will give you an example. I have a jet boat. 65 horse jet outboard. The same engine with a prop foot is rated at 90 hp.

Still, I love jets, even if they aren't efficient. Hit the ventilator, shoot a rooster a mile long. I also love the idea of a jet GT-21. One thing in a jets favor is longevity. No drive will ever hold up as long as a jet. BTW, Jacuzzi made a hell of a jet and there are still plenty of rebuild kits available for them.

Good luck.

[axelkloehn]

No, not unless you have HUGE power. I read about your inquiry about the efficiency of jets on the other thread. They lose about 25-30% of prop hp over a regular stern drive. Plus, you are dealing with 1970's technology, whihc is probably even less effecient than todays jets.

I will give you an example. I have a jet boat. 65 horse jet outboard. The same engine with a prop foot is rated at 90 hp.

Still, I love jets, even if they aren't efficient. Hit the ventilator, shoot a rooster a mile long. I also love the idea of a jet GT-21. One thing in a jets favor is longevity. No drive will ever hold up as long as a jet. BTW, Jacuzzi made a hell of a jet and there are still plenty of rebuild kits available for them.

Good luck.


Ok, if I cannot solve the installation problem due to the fact it is too long for the GT21 engine room, I guess I keep the jet for a future fun project- may a little 16" footer with a 302 engine just for the fun having of having a funky jetboat.
The GT is almost done with installing the Bravo anyway, it was just that I got the jet with the olds engine for 500$ extra which made me consider the original jet-package. Anyway, Jets are quiet rare here in germany, not too bad having one... :wink::wink::wink:

[mrfixxall]

Oh Mr. Fixx, I was checking the technical drawing for hours to find the way to shorten the Jet or the coupler, couldn't find any way to gain at least 10" needed for proper installation. I thought about making the double cardan joint a single one or lining up with no cardan at all.
Your idea is very good but might not work on my jacuzzi (see pic). Hmmmh, or may be I did not understand exactly what you mean...

Another question: do ya guys think the GT because of its weight will go 65-70 mph with the Olds/jacuzzi package? That is what I am aiming for without having a short lived engine....


sorry it looked like the coupler was longer in the pic..you could take the coupler apart(ujoints) and use only 1 ujoint but the engine to coupler to pump spline would have to be perfectly aleigned so you get no viberations..

[axelkloehn]

sorry it looked like the coupler was longer in the pic..you could take the coupler apart(ujoints) and use only 1 ujoint but the engine to coupler to pump spline would have to be perfectly aleigned so you get no viberations..

Hey, no problem, I am glad you guys are helping and I am not getting on your nerves with my GT/Jet blabla. This website is fantastic and I am feeling, although I live far away from you guys, I have found friends with same minds... I am adicted to this site and I love sharing my time and my hobby with you all.

Anyway, using only one ujoint is a gain of 2", still 8" missing :boggled::boggled::boggled:.

Well, Oktoberfest just started, Jetdrive can wait a while.... I do need some beers to get into it again.

:beer: Axel :germany:

[MOP]

Ok a little inboard experience! you do not need U joints, you can use a flexible coupler to gain quite a bit! Below is an example, there are a few makers out there. Get you mouse clicking you can beat this!

Phil

http://www.flexible-coupling.com/r-and-d-flexible-shaft-coupling.html

[Ernie]

I spent a lot of the 70's and early 80's with jet powered boats. None of them with deep v hulls. Sea Ray had a 19 ft deep v with a jet pump. You had to give it more than half throttle just to stay up on plane. Ninety % of the Jacuzzi's were the big Y pump. Not good for speed, but would move a lot of weight around. G pump from Berkley was and still is I believe, the pump of choice by the racers. Believe me, your much better off with an outdrive.

[axelkloehn]

I spent a lot of the 70's and early 80's with jet powered boats. None of them with deep v hulls. Sea Ray had a 19 ft deep v with a jet pump. You had to give it more than half throttle just to stay up on plane. Ninety % of the Jacuzzi's were the big Y pump. Not good for speed, but would move a lot of weight around. G pump from Berkley was and still is I believe, the pump of choice by the racers. Believe me, your much better off with an outdrive.

Yep, it looks like this is the way to go. Thought a lot about using my jet but it's more installation trouble than with the outdrive- Engine room is just too short and I am not cutting the cabin wall off. And it's good to hear your experience about deep Vs with jets.

Thanks, Axel :germany:

[MOP]

It is good to see you are the type of gut that gets right down to business! Again good luck with the resto!

Phil