Pacific jet drive

Dt125 · 13 October 2004, 18:19

Just out of interest, has anyone out there ever fitted a jet unit into a mk1 pacific? Or does anyone know how easy it is to do? I like the idea of having a jet instead of a leg but cant quite afford a mk2!

Pete7 · 14 October 2004, 08:02

Quote:

Originally Posted by Dt125

Just out of interest, has anyone out there ever fitted a jet unit into a mk1 pacific? Or does anyone know how easy it is to do? I like the idea of having a jet instead of a leg but cant quite afford a mk2!

Never fitted one, but drove a P22 that had been converted by James Warlock of Lymington. Real laugh but a complete disaster. Thank god I didn't buy it. Thing wouldn't go in a straight line, mooring it was impossible and the drive would make the boat go starboard when as soon as the engine was started.
To be fair the boat need a lot of sorting and even with a "claimed" 200 hp engine it only managed about 15 knots.

Pete

Scary Des · 14 October 2004, 08:37

Quote:

Originally Posted by Dt125

Just out of interest, has anyone out there ever fitted a jet unit into a mk1 pacific? Or does anyone know how easy it is to do? I like the idea of having a jet instead of a leg but cant quite afford a mk2!

I looked into this in some detail because when I bought my boat it didn’t have a leg and because I would have prefered a jet to a leg.

Looking at the various jets available I think that the Hamilton jet, although expensive, was definitely the best designed and strongest jet available so I based all my thinking on this.

To start with there is room in the P22 to fit a jet so there would be no need for major internal alterations. And things like lining up the prop shaft were all possible.

However, to fit a Hamilton you have to cut a hole I the bottom of the rib in the planing foot and this is where I started to run into installation design problems. By cutting a hole you are reducing the area of the planing foot and this has to be made up elsewhere or the boat will not plane in the same way as before. On the MK2 Pacific’s the planing foot is longer and wider than on the MK1’s and there are also two small skegs on either side of the jet inlet to stop side slip. Doing this to a MK1 would take a lot of glass work and this is what finally put me off the idea.
Jets get a lot of criticism and in the case of the one James Wallrock had for sale it was probably justified, but you have to ask yourself why have the Navy started using them if they are as bad as some people think.

Incidentally I met the guy who bought James's rib he was trying to sell it for ages, anyone know if he still has it?
Des

Pete7 · 14 October 2004, 08:50

Nope Phil managed to get rid of it thankfully. I just hope no one on here buys it.

Pete

Scary Des · 14 October 2004, 08:57

It was dreadful, I think James just put all the spare parts he had available into one boat and hoped for the best, might explain why he ceased trading. Des

Pete7 · 14 October 2004, 09:10

He offered it to me for £10k. Because the hull has a jet drive there was no bung in the transom to drain the hull. It had clearly been sat outside in his yard for some time because the hull probably had 400 gallons of water in it which had filled up the whole hull and was over the top of the alternator and starter. Suprisingly it did start

I politely explained to him that he must be joking. Think the boat is still in Southampton.

Pete

Pete7 · 14 October 2004, 09:43

I think I would really want to trial any jet boat before parting with hard earned cash and the thought of spending months of work converting a hull only to find its a disaster doesn't bear thinking about. I suspect halmatic have had to modify the hull for very good reasons.

Pete

Scary Des · 14 October 2004, 09:44

Quote:

Originally Posted by Pete7

........ I politely explained to him that he must be joking....
Pete

James always did have a sense of humour

Des

Searider · 14 October 2004, 10:41

Another thing to bear in mind is that a jet will almost cause a boat to run "stern heavy" because:

1. The hole cut in the bottom of the boat and the water jet tube reduces the buoyancy at the rear of the boat and

2. There is a virtual increase in displacement caused by the water passing through the jet having to be raised from the inlet to the outlet as well as being propelled aft.

The above are not a problem on a hull designed to take account of this but "may" be a problem on a retrofit.

Dt125 · 14 October 2004, 19:17

Wow, sounds like a bit too much head scratching to me, think i'll just stick with the old sternpowr! Nearly up and running again now anyway - only bought the boat in july and its been out since the beginning of august after my bearing housing fell apart

Anyone know a quick way of bleeding the tilt rams? ive run the batteries down twice now just moving the leg up + down for ages and it still wont go all the way up on its own???
Pete 7 hows your engine after the crank seal went?

Scary Des · 15 October 2004, 11:46

Quote:

Originally Posted by Dt125

........... Anyone know a quick way of bleeding the tilt rams? ive run the batteries down twice now just moving the leg up + down for ages and it still wont go all the way up on its own??? ..........

Never had a problem with bleeding the tilt rams once I got them working.

I had some remanufactured ones that were not put together correctly and they were doing the strangest things

You can check operation by putting an air line on one inlet and if air comes out the other side all is not right. Having said that there is a crash valve in the ram which will blow off at high pressure (can’t remember what) so you don’t need lots of pressure to find the fault.

I did have a problem with the external hoses, if you don’t get the runs right they can pinch. And another thought is have you got sufficient oil in the system

stupid question I know but there is not a lot of reserve capacity

Des

Dt125 · 15 October 2004, 19:53

Hi Des, Yes there's plenty of oil in the reservoir, i tried slackening off one of the low pressure hoses on the end of one of the rams and when you switch the leg to raise it, oil flows out. Should this happen??

Scary Des · 18 October 2004, 12:56

Quote:

Originally Posted by Dt125

Hi Des, Yes there's plenty of oil in the reservoir, i tried slackening off one of the low pressure hoses on the end of one of the rams and when you switch the leg to raise it, oil flows out. Should this happen??

If the ram isn’t moving and oil is coming out then I think you have a problem.

If the ram is moving it is only the oil on the other side of the piston being forced out.

Having said that I had no problems bleeding the system I remembered over the weekend that to start with the leg went up quite slowly and I got a mate to lift it while I operated the switch maybe this is worth trying

Des

Dt125 · 18 October 2004, 17:40

Des,
Thanks for that, i got someone to help lift it and its been working fine this afternoon, got her in the water and shes running SO much smoother than before, its great! Having said that, shes only coming up to 2000 rpm at WOT where as she used to do 2400. Possibly dirty fuel filters?? I also replaced a section of fuel line with narrower pipe which may not be letting enough fuel through. Have to see how she goes over the next few days, Cheers DT

Seb · 18 October 2004, 18:08

Am i right in thinking that some jet units are transom mounted only rather than half external, half internal?

If so, then converting to such a jet unit would be feasible as it wouldnt interrupt the planing wedge of the hull and would require very little modification to the transom.

Only downside is that the jet couldnt be a Hamilton.

roohairy · 18 October 2004, 22:14

The P22 with jet drive built by James Walrock was lying in Extreme Marine's yard, the hydraulic control system had expired. Looked otherwise ok, tubes tatty. Have some pics if anyone wants them.

Scary Des · 19 October 2004, 08:06

Quote:

Originally Posted by Dt125

............. 2000 rpm at WOT where as she used to do 2400. ........... I also replaced a section of fuel line with narrower pipe which may not be letting enough fuel through............

Not good

these boats have a reputation for fuel problems so I would get the right size pipe ASAP.
Assuming filters are ok it is worth air-lining the fuel lines back to the tank because at one time the Navy used a wooden dipstick and the result is that the tanks are often full of little slithers of wood

.

Other things to check are that all the fuel fittings are tight especially the ones from the lift pump onwards, these use a neoprene olive and I think they can become loose equally it is difficult to know how tight they should be

.
On the pump there is a pressure relief valve which holds pump body pressure at about 10 psi this will often block and is overlooked when servicing. If blocked this will knock 200-300 rpm of the engine but seams to have no other major effect.

This valve sticks out of the side of the pump and has a fuel return pipe on the other end.

Des

Dt125 · 19 October 2004, 18:54

Tried her out again today and she came straight up to 2400rpm no problem. Been playing around all day and not had any problems at all. Could have possibly been an air bubble in the fuel line??? Not sure but all seems sweet now! Not sure what size the prop is but its slightly bigger than the standard 17 3/4 x 21" and im getting 28kts no problem with just me on board, but i think thats stopping her from going above 2400rpm

Roger · 19 October 2004, 22:08

Wilst on the subject of props, my P22 Prop has Michigan 032109 stamped on it,I have tried Michigan Web site and Google search no info, can anyone tell me what pitch it is, the diam is about 19 inches. It gives approx 22 Knots @2000 rpm.

Thanks Roger

Pete7 · 20 October 2004, 12:25

Roger, I have the same problem with one of my props. Its going to Steel Developements shortly for a repair so I will ask them to measure it, but it sounds like yours is 23 - 25 inches and probably a bit tall. The best prop I have found at the moment is a 16.76 x 21 which allows the engine to reach max revs of 2600.

Pete