PP65 upgrade

I have a West End Marine ~Striker II from what I gather from this forum it’s a copy of a Dateline Bikini. The jet drive has West End embossed into the reversing bucket but to all intents and purposes it looks like a pp65 except the access hatch is square and hinged rather than round and bolted. Anyway I've had the boat a number of years and it goes quite well, when I bought it the engine was completely shot big end seized up so over that winter I stripped and reconditioned it. it’s a 3L Essex V6, to cut a long story short i increased the horsepower from the stock 140 to about 220, Big valves, upgraded valve springs, hardened valve seats, high lift stage 2 piper cam, inlet manifold with three weber carbs, steel timing gear, crank re-grind, re-bore, new pistons etc engine runs great. But the boat's performance is sluggish to say the lease, well compared to other jet boats I’ve ridden anyway, it does get up to 25+ mph eventually but the engine is revving its guts out 5500RPM with more room to go on the throttle but i daren't push it that high so as not to over rev the engine. Basically I have to open throttle slowly or i get cavitation and go nowhere fast. In order to get up onto a plane i have to open the throttle in three stages and let the boat catch up. It seems to take between 20-30 seconds to get up onto a plane. Once on the plane it does go quite well but i need more thrust in order to get a skier up or tow inflatables and thrust seems to be something it lacks. It seems with the mods the engine is too powerful for the jet, and the intake diameter seems rather small compared to the outlet nozzle, is it a case of being unable to suck in enough water? That’s what it seems like. I have adjusted the three bladed impeller so that the blade tip clearance is about 0.5mm-1.0mm can't get it closer without it scraping the wear ring.

Unless I have overlooked something my thinking is i need a bigger jet drive so i have finally managed to get hold of a Hamilton 771 which at first glance looks like it should run rings round the PP, the intake scoop is considerably wider and longer same for the duct leading into the impeller. apart from the major surgery to the boat to install the Hamilton is there anything i should be aware of? it looks as though i will need to move the engine at least 12" to 15" forward which means losing the rear passenger seat, but i think moving the weight further forward will improve the trim. The sturn always sits low in the water so much so the exhausts are below the waterline, not good for the engine when its stopped and makes it more difficult to clime onto a plane because the bow is up in the air. Also it seemed like a bad idea having water going up the control cables leading to annual replacement from corrosion. I look forward to hearing your views, is this a wise course of action? Before i start work on the conversion this winter. Mike

 

Hi Mike and welcome to our forum.

Your problem is a far too small jet. Even with the original 140 hp or so, it is on its design limit, both in terms of power and rpms. Your engine mods didn't make life easier for it...

Now the alternative: the Hamilton 771 has a 190 mm impeller and is limited to 130 hp/5000 rpm; it won't work either. But the 770-series can be stacked, and for you the 2-stage 772 might work quite fine. If you can get your hands on a really good (note corrosion and general wear) 771 for decent money, it might be possible to find 772 spares to rebuild it. A "copy" was produced in the US under the name of "Turbodrive" pre 1989. Also produced by "KEM Equipment, Oregon" under the name of "Kodiak".

Better still would be a Hamilton 221. It is a newer design, with a variety of impellers and parts available. But note that, contrary to common belief, jets do not like high rpms; I'd say that to get a working combination, you should aim at about 5000 rpms at max power; better less than more.

 

Hi Baeckmo,


Thank you for replying, you confirmed my suspicions so a bigger jet is the way to go, the 771 is in very good condition for its age, original paint with Hamilton 770 logo printed in colour on the reversing bucket, a bit faded and a few minor spots of aluminium oxide showing through the paint its obviously spent most of its life out of the water. I picked it up from ebay for £700. Before i bought it i got in touch with Hamilton UK and apparently pretty much everything is still available for it, impellers £450 , wear rings, seals, bearings etc I wonder if that would extend to a longer shaft and second impeller casing to make it into a 772, or push the boat out and turn it into a 773 so i could put it on a bigger boat in the future, defo worth asking. At the time I enquired about spares I got a quote for the HJ213 as that looked like the jet i need but the cost is an eye watering £8471 plus vat! How can they justify that kind of price? its nowhere near the complexity or precision engineering that goes into making an engine. That was what made me grab the 771 while it was available. Although the service manual says its limit is 130BHP comparing it to the PP65 it looks like it should easily handle 200bhp. but i guess that’s because it does when its loaded with two or three impellers. Do you think it will cavitate in the same way as the pp if i open the engine up or do you think it will work better?.

 

Another aspect that made me go for it was that the 770 service manual quotes the 771 having better performance than my boat when fitted to a boat with a displacement of 2 tons whereas mine is prob only 750 kilos so it must be developing considerably more thrust than the PP for a given input power. Is this the case or is a longer but heaver boat easier to get onto a plane?

 

With the effort needed to convert the boat to another jet, it would be stupid to fit the 771, considering its design limits; it is a nono! But since you already got the 771 unit, collect the bits to upgrading to a 772, then you will have a suitable setup.

I would not consider rebuilding to a 773 version; better to find a suitable jet for future boats, than fiddling with with something that "may or may not fit".

On the hull/length/weight issue, there is one parameter which is paramount for the jet performance envelope; the slenderness ratio. It is calculated as: (waterline length)/(displacement volume)^(1/3). Low slenderness (ie short and heavy) hulls have very high resistance in the pre-planing speed range, often higher than at high speed. With too small "swallowing capacity", the jet will loose thrust due to cavitation when trying to get over the resistance "hump".

The power density in the jet impeller is extremely high; you are asking a small rotor of less than five kg weight to transfer the output from a 400 kg engine with trillions of rotating, vibrating and jumping-up-and-down paraphernalia. There are simply limits to what can be done, even if vortex motion is one of the most energy-dense phenomena in nature! So; If it is worth doing, it is worth doing well......!

 

Thanks for your advice, I’ll fit the 771 its got to work better than the PP currently does in my boat according to the formulas in the 770 workshop manual. And I will keep an eye open to obtain the bits to upgrade it to a 772. The engine weighs in at 170kg so it has excellent power to weight ratio. I'll keep you posted on any progress.

 

Hey Michael,
I was wondering how your conversion to the hamilton 771 jet worked out?

 

Hi Rebrandt,


Sorry for the delay in getting back to you.

Kept an ear to the ground re-upgrade bits for the 771, although the impellers are available the stator blocks are not and have been unable to find any second hand 772 bits (shaft, staters, studs, control rods etc). Also, a lack of time (work) prevented me from fitting the 771, as Baeckmo pointed out the 771 as it was, was under powered so I didn't feel inclined to find the time and make the alterations to fit it. Boat is fast once you coax it up onto a plain. Got a fair bit of use out of it in 19 and 20 espeicily with the pandemic.


Was continually having problems with weed on the intake grill, so after considerable deliberation I removed it, that made a big difference to performance, no cavitation and much more responsive, goes straight up onto a plain and even goes better in reverse! And the weed passes straight through and gets chopped up without clogging. I’m not concerned about sucking stones and gravel as there is no shallow water where I use the boat, and I cut the engine before I approach the slipway.


A Vospower PP90 in good condition has become available but I’m concerned that the extra weight (50lb) will make the boat trim even worse plus the outboard portion is 8" longer. Guess I could still move engine forward to correct for that though.


With the present setup it seems with extended running at over 5000RPM i have a problem with flywheel bolts working loose. The bolts are extended and pass through the hub of the donut coupling. i used Loctite thread lock but that didn't help, am thinking now to drill holes in the hex heads and wire them together. I also had to replace the bearing and oil seals in the jet drive.


Mike

 

Ok have finally got around to fitting the Hamilton 771 unit into the boat and boy what an improvement in performance though it was hard work, and took longer than anticipated. can post pix of the conversion if people are interested. I do have a couple of issues though, one is i can’t lower the reversing bucket below the neutral position if the engine is running at idle it just won't drop and I feel I’d break the reversing lever or control cable if i really force it, i can see its mounting bending. If I stop the engine it goes from forward to reverse without a problem, but surely you should be able to do that without stopping the engine sometimes I can't get it to go to the neutral position, it’s as if the water coming out of the jet is trying to lift the bucket.


Secondly there is a wired handling anomaly when going at speed (30 + mph), when going straight the boat tends to list to the right (drivers’ side) without going around a corner even with a passenger so the boat is balanced weight wise. If you turn to the right the list angle becomes alarming and tilts quickly so much so that you feel if you turn too tight you might capsize and considering how much the boat is tilting it’s not turning very tightly, turning to the left is fine and feels very solid and can do really tight turns. Any ideas anyone? Is the torque of the engine tilting the boat?


By the way i have two brand new (still in original crates) Naiad Dynamics/Vospower PP90 jets for sale if anyone is interested.

 

Could this be a similar problem to the Searader thread? I have only got a couple hours of use on the jet so far, not long enough to have cavitation marks to appear on the stator yet. I think the boat had a tendency to tip to starboard with the previous pp65 jet when the engine was maxed out but as the top speed then wasn't so high it was barely noticeable. and as the engine was revving very high i rarely ran the boat that fast so it was not a problem, now i go through that speed threshold at around 2/3 throttle and the rest of the throttle range is usable as the engine is heavier loaded so does not rev as high. Throttle wide open revs are 5200 RPM but at that speed i would not want to imitate a turn to starboard as it already has up a 30 degree list to starboard, also the list seems to oscillate, it will pitch down, then go back to level then pitch down again, when going slower boat is level but it still does not turn to the starboard as tightly as it can turn to port.

 

Hi Mike, nice to see your improvements. The listing can not be traced to the engine/jet combo though; the stator compensates for the input torque in a jet. From your description, my spontaneous reflexion is that something is wrong with the spray rails and weight distribution. Could you give us some more info on the hull? Pictures?

 

Hi Baeckmo,


Great to hear from you and have your input again on this project. At the moment the boat is in the shelter and currently blocked in with another vehicle but I’ll move things about and move it outside tomorrow it’s on its trailer so that will restrict the view somewhat. When you say spray rails, do you mean chine lines? I have attached some pix i took during various stages of the conversion, i don't have a side view of the hull as such but will try to take some tomorrow.


You might wonder why i built the wedge-shaped box on the transom that the jet is poking out of, the reason was the outward angle of the transom was greater than the angle the seal ring on the jet could accommodate, and there would have been gaps top and bottom where the rubber seal would miss the ring on the jet all together. To angle the front of the jet up enough so it sealed against the transom would make the engine unduly high in the boat and the water exiting the jet would have a considerable downward pitch. Also, that would have necessitated mounting the front foot of the jet scoop higher than the bottom of the boat which might have caused turbulence to the incoming water, as it is the front foot of the scoop is flush with the bottom of the boat, I cut out a triangle from the bottom in front of the scoop which goes from the point of the V towards the front to a flat line flush with the bottom edge of the intake as described in the Hamilton workshop manual on installing the jet. So i built the wedge-shaped box so the jet can push the water out horizontally, parallel to the bottom of the hull. The box bottom follows the V angle of the hull and is smoothly blended to the hull so it just becomes an extension of the bottom of the boat.


Can you let me know what pictures you'd like me to take? I have included the boat on the water pix to give you an idea of the trim both when going at speed admittedly not maximum as its towing a banana with two heavy guys on it. and one at rest just after launch.


Look forward to hearing from you.

 

looking at the engine/jetpump/self bailer pic you might think the engine and pump are not mounted on the center line of the boat, infact they are its just the spacing of the engine barers is un equal as the engine is wider meashured to the crank on one side than the other.

 

The outboard bracket is a square that fits round the starboard exaust port, it does have a horazontal brase accross the middle but when the boat is plaining i would have thought it would be totally clear of the water. and does appear to be from planing pic.

 

looking at the plaining pic i don't think its something as silliy as the prop on the outboard dragging in the water, if it was i think it would have had so much force and vibration as to break the outboad bracket or rip it off the transom.