Author Topic: Jet boat perils  (Read 1752 times)

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Offline BN

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Jet boat perils
« on: April 13, 2016, 09:32:18 PM »
I have had a huge amount of problems with the restoration of my Dowty's. In the end, I have given up on one and the pictures show why. The engine has a split block, plus much more and is virtually scrap, this is the 3rd Zephyr that I have had with splits blocks. Possibly because the raw water is fed into the engine and when stopped with a hot engine the cold water destroys the block when started again. Also the jet units are very difficult to set up. In the end, I have cut one out and I can see why now. The cork gaskets leak around the hull seal and there is almost no way of removing the 42 bolts to replace it, which are frozen into the jet housing. Two of which are hidden. The picture shows fibreglass in a sad attempt to seal the leaks. With the power of the twin stage jet, fibreglass just is not going to work. Notice even one of the securing bolts on the jet pump has broken, which in fact could be quite dangerous.

One thing is that the hull is so thick, it should stand some very serious abuse.

Anyone else found these problems with their Dowty?
1953 Albatross
1958 Dowty Turbojet
1965 Mitcham Jetboat
1968 Mitcham OB

Offline BN

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Re: Jet boat perils
« Reply #1 on: April 16, 2016, 04:16:34 PM »
An interesting comparison of the Dowty jet unit and a jet ski jet unit.
1953 Albatross
1958 Dowty Turbojet
1965 Mitcham Jetboat
1968 Mitcham OB

Offline stevem3akm

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Re: Jet boat perils
« Reply #2 on: April 22, 2016, 10:41:21 AM »
Hi, just a thought but would the blocks repair and would converting to a closed cooling system help? Regards Steve

Offline BN

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Re: Jet boat perils
« Reply #3 on: April 22, 2016, 08:14:36 PM »
I had thought about making the cooling system a closed one, but it is not going to be original. Having said that, restoration can be upgraded of course and it is a good idea  :D

The blocks can be repaired, but the cost is out of this world. Stitching is an option. My farther could do it, but I cannot. To have the block welded requires heating in an oven, then welding and then cooling down, There is a great company in the Midlands who do it, but the cost  :o
1953 Albatross
1958 Dowty Turbojet
1965 Mitcham Jetboat
1968 Mitcham OB

Offline stevem3akm

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Re: Jet boat perils
« Reply #4 on: April 24, 2016, 08:34:41 PM »
I restore old cars for a living so I fully understand your quest for originality, but if it means a lot more reliability l would think it's worth considering, I know I shall be converting my Capricorn to this system. As for the blocks, there is Company localish to me, Lockstitch of Rochdale, that are very good and reasonably priced. Best regards, Steve

Offline BN

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Re: Jet boat perils
« Reply #5 on: April 25, 2016, 09:23:58 AM »
Good points and good to hear that a professional has similar views. The detail of the repair company is very good to know and if you could place it in the post I am sure people would appreciate it.

I should start a useful contacts board as well with such important data.
1953 Albatross
1958 Dowty Turbojet
1965 Mitcham Jetboat
1968 Mitcham OB