Help!! Jet Drive Broken!!

Help!! Im new to this and Im having problems with my hamilton jet drive. The Jet is in a 15ft speedboat, mated to a 3.5l Rover V8, and has 4 blades on the impellor. I am unsure of the type of jet drive it is, so have attached some photos hoping someone may be able to identify it?

The problem i have seems to be excessive play in the impellor shaft, which has caused the impellor to drop and rub on the casing at the bottom. Does this sound like a normal problem?
Any ideas of the cause?
And is there anywhere that specialises in parts other than Hamilton?

Im having to rev the engine harder to get the same results.

Any advice or info would be great.

Many thanks
Chris

 

Hi
One of your two bearings is broken ,almost certainly the rear cutlass bearing,this is a standard bearing available at any marine workshop,the hard part is getting the old one out,they are always corroded in ,especially with a jet of this age ,using the boat is not a good idea you will cause damage to the impeller,wear ring ,and romet seal

Good luck

 

Thanks for youre help! Do you know what type of jet drive it is?? Are parts for this jet drive only available from Hamilton?

 

Hi
From the photos it looks like a hamilton 7 series from the 1970's Most of the parts needed to maintain these can be found at bearing suppliers or marine workshops the exception to this is the carbon faced romet seal ,great care should be taken with this they are very fragile.and expensive hopefully you won't need one,and if it ain't leaking dont touch it.
If you remove the tailpipe it will be obvious if the cutlass bearing is your problem ,remove the metal bearing sleeve on the shaft and check the fit in the cutlass bearing if it is not a nice snug fit replace the rubber bearing.This is just an interference fit in the tailpipe ,unfortunately the aluminium "grows " around it and it can be hard to remove. Warming gently WD40 and some kind of slide hammer arrangement can sometimes work ,but in the end you will probably end up with a hacksaw blade in a padsaw handle.Cut a slot in each side of the bearing and its bronze or brass housing and then with a punch GENTLY try to collapse it inwards.This will break the seal at the sides and it should pull out Take the old bits of bearing to a good commercial chandlers and they should match it,these are normally about twice as long as you need so cut it in half and save the spare bit for next time
Finally make sure the hole in the rear of the stator bearing housing is clear,this allows a flow of water to cool and lubricate this bearing AND NEVER RUN THIS JET OUT OF THE WATER
If you need any more advice ask

Regards Tony

 

Unit is an Hamilton jet 751. The gate steering gives it away. the '1' designating a single stage.

As mentioned the cutlass bearing is most likely worn. When checking this, remove the chrome sleive from the mainshaft and insert it into the tail pipe, they should be a tight fit, if not it's time for replacement. Also check the chrome sleive for wear or chips out of the chrome, if so these will need to be replaced. Be sure to use chrome sleives rather than stainless ones, as the chrome is harder than stainless and therefore not subject to the same wear.

If it's not the cutlass bearing then it may be that use in salt water has caused the wear ring to 'shrink' (usually starts at the bottom) due to salt build-up between the stator housing(or this case, tailpipe housing) and the stainless wear ring. In this case, remove the wear ring and insulator, clean away the salt (may need a lathe to ensure round, but not strictly necessary), insert new wear ring and insulator using an hydraulic press. Don't forget the insulator!

Either way, it is most likely that the impellor will need a re-build. These units are real fickle about the OD / ID tolerances. I usually rebuild the impellors to 'crash' with the wear ring, then 3 seconds of the motor running creates the correct clearances.

I must re-iterate NOT to run this unit out of the water, I've seen plenty that have been run and replaced the cutlasses and rebuilt the impellors on them all.

 

Thanks for youre help guys, you were right it is the cutlass bearing.

Does anyone know anywhere where I can get one except Hamilton themselves?? They cost £140 from them. Does that sound about right??

Seems quite a bit for just afew iches of metal tube with a rubber insert. Should most marine dealers be able to supply one, or is it a manufacturer part only?

Thanks again.

 

Hi
As I said before there is nothing special about this bearing this is just a standard cutlass bearing .go to your nearest commercial chandler with the old bits to match it, if this fails A.S.A.P supplies do a huge range they are in Beccles in Suffolk but they do mail order. google ASAP supplies for the full address
This is not an expensive item,the last one I bought was about £20 but this was a few years ago
Make sure you measure the inner and outer accurately before you order the length doesn't matter just cut it

Good luck Tony

 

It just occured to me I would guess that the guy "SPEEDBOATS " from New Zealand that replied to your post could probably give you the dimensions,on a jet of this age they may be imperial rather than metric
Tony

 

yes, they are an imperial measurement.

2 1/2" from memory, the mainshaft is 1 3/4", and the chrome sleeve's OD is 2"

 

Just looked above and remembered yours is a single stage, most likely you'll have the small mainshaft @ 1 1/2". The cutlass bearings are still the same, the difference is taken up by a thicker chrome sleeve