Jetstar boats

[alanr]

well it won't be any faster or more economical
but better for engine life.

[enginuitytriumph]

I'm hoping for a less noisy more relaxed cruising speed.... Looking at the cam profile, it tops out of puff at 5750, so it could be more effective at 5000, we'll see next outing. 
    I see what you mean about the Stainless Steel impeller, it weighs a ton !! So I might try it for a few minutes, but I can understand the prop wind up with that thing on the end of the shaft.
    I can't believe how easily the impeller comes off ! I've ended up "cutting off" propellers to save an outboard leg & these things fall off with a sneeze!
   I've done a deal with Lancing Marine for the gears, so I'll get the lump out. Should you change oil, seals  & gaskets? Thanks.... Mark

[alanr]

Don't normally have to change the seal but pull the cover off gently and you
may well not need a gasket either but just a bit of silicone sealant
when it goes back. You will need a 3 legged puller to remove the thrust
bearing. Make sure the gears are helical cut and not cross cut as they were
very noisy. Also if they are used gears check the dog clutch faces. Let me know if you need any help.
Alanr

[enginuitytriumph]

I got the gasket & seal as well as they were thrown in for free!   However, they are straight cut gears I'm afraid ( I did think they might be noisy, but didn't know if they were already like that !!  Apparently they are new / old stock. While I was there though, I had a look through the  'Castoldi 05' shelf to see what goodies where there & I saw a modified jet cone.   It had the outlet hole made smaller & on it was written 'good for water skiing'.  I asked Mike what that meant & he wasn't exactly sure, Gordon Thurkettle had modified it when he was there & was playing with different things.   He did think that the smaller outlet hole would mean better 'out of the hole' & less top speed, but  I thought I'd be better off asking you !!    

[alanr]

you will find the gears whine a lot. I don't think you will like the noise.
I modified a nozzle from an 04 jet to try to increase thrust but it made
little difference and actually lowered the top speed due to decreasing
the ejected volume of water. Castoldi jets are pure axial flow so the more
water it throws out the faster the boat will go. Leave your nozzle as it is.
Basically when designing an axial flow jet the impellor matches the intake
and the nozzle matches the impellor. Castoldi got it right with the 05
jet so I don't think you will make it more efficient than it is.
During the early seventies we involved Professor John Stollery at Southampton
University to look into different impellor designs but he could not
better the standard Castoldi design.
If you use the s/s impellor remember not to engage the clutch with the engine
running. Always start the engine with the clutch engaged to avoid 'wind up'
and damage to the shafts and rubber donut drive.
Alanr

[tjennen]

Hello,

Do have any idea if this is a Bluebird Marine ? Any type. Bought it without engine but last mounted was a Johnson 140hp.

[alanr]

Hello, although it is similar to a Jetstar 520 it was not manufactured by Bluebird Marine.
I have seen other identical hulls on here but it seems they are copies with hull and deck modifications
made to avoid problems with design rights. I would be interested to see a stern view picture.
 Alanr

[tjennen]

Like this?

[BN]

That is a very unusual stern and looks as if it may have been an inboard, but later chopped to accept an outboard. However, Alanr is on the case and I am a little mystified 

[tjennen]

MB Shark is on the papers. From 1970

[BN]

At this point in time, I am struggling with the make of boat. It is a great style and super hull, but no idea. Normally with a bit of research I can come up with an answer, so lets see what happens 

[alanr]

Thanks for the stern pic. The hull is a deeper V than the Jetstar at the transom. Both Jetstar 13ft
and 17ft hulls were of the warped hull design which starts off deep V then flattens out gradually to 15 degrees
at the transom. Peter Milne got the design absolutely right with those hulls. It was more difficult to make the original plugs than a constant deadrise V hull but much better performance.
The bow section and topdeck/dash front section are copies of the 520 but the rest is different.
No idea who made this boat.
Alanr

[BN]

Hi tjennen, it looks as if we have a boat of unknown make right now. I know some of the Dutch yards built boats using various other boats designs and even components, but yours is still a mystery 

[tjennen]

You can't make everything easy he .

do you have an idea what the weight would be +- ??

[BN]

Possibly around 500kg without and engine??