Hunton/ilmor Build

[Jon Holmes]

Thats a lovely piece of work.

[Boatless-Again]

Originally Posted by peterunwin

Hi Boatless,
In a small light boat travelling at fairly modest speeds you can manage without check or counter balance valves but the bigger faster boats with out drives such as the Merc and the Ilmor where the propellor sits way behind the steering pivot there is so much sideways force created by the propellors & the lower unit that if you don't control that force with a check or counter balance valve the helm unit would be turned in to a hydraulic motor causing loss of control of the boat & potentially serious injury to your hands. In my installation there is no helm unit as it is flyby wire, the hydraulic circuit is between the cylinders via the counter balance valve to the directional control valve. The counter balance valve has been chosen for this installion because it has zero freeplay, i am also engineering my own tie bar between the drives using stainless steel spherical ball joints this will be mounted aft of the cavitation plates which is the furthest point from the steering pivot.Keeping good control of the drives will save the control valve from constantly adjusting itself to keep the boat on track it will only steer with an input from the wheel not by external forces.

Peter

So, the valves isolate or remove the feedback the propeller torque/thrust/side load exhibits onto the hydraulic system in means of back pressure?

I never see a check valve on the helm units or a counter balance valve on Merc system other than on the p.s. pumps to eliminate flow back.

[PerformanceDodge]

Originally Posted by peterunwin

Hi All,
Started fabrication of the water pickup pipes, they are made from 1.25" OD stainless tube bent to about 110 degrees this added to the transom angle of 14 degrees gives quite a good scoop effect.When they are fitted the front of the pipe will be level with the bottom, the rear of the pipe is about 1/4" lower which i may need to reduce if i have too much water pressure, also had a mock up of the spark free battery isolator switches.

Peter

Hi Peter

Firstly I must say what a stunning job you are making of you boat, it really is a work of art and can't wait to see run. I was just looking at your water pick ups and wonder if I could possibly ask you opinion. As you possibly aware from the forums I am converting a cougar 225 to inboard engine and using a sealed water system with heat exchanger. The engine a 3 litre Mercedes turbo charged diesel with charge cooler and is expected to be 270bhp max. The raw water will first flow though the charge cooler heat exchanger then trough the main engine heat exchanger, the engine has a built in oil cooler heat exchanger connected to the sealed system.

I notice you have used 1.25 inch O/D tube for you water pick ups with probably 1.125 inch ID and you engines produce 725bhp. The inside cross sectional area of your pick ups would equate about 1 inch.

I wonder if you think I will get away with 0.875in I/D which equates to 0.6in Cross sectional area, which is 60% of the size you are using. On the one hand I will be running well under half the horse power and with a diesel which is thermally more efficient, but on the other hand, I will be running a charge cooler too.

In you opinion do you think this size would be OK for my pickup up and run through the whole system.

Look forward to you reply.

Regards David

[peterunwin]

Originally Posted by Boatless-Again

So, the valves isolate or remove the feedback the propeller torque/thrust/side load exhibits onto the hydraulic system in means of back pressure?

I never see a check valve on the helm units or a counter balance valve on Merc system other than on the p.s. pumps to eliminate flow back.

Hi Boatless,
That's probably because they are usually built into the helm units and unless you know where to look you would probably not spot them, as i don't have a helm unit i am using a much larger external valve. An easy way to test whether a system has check valves is to try and move the drives manually where you would normally get a small amount of free play as the check valves seat, but i have to say having had numerous boats with Seastar or Danfoss steering systems they have all had check valves.

Peter

[peterunwin]

Originally Posted by freddy21

Hi Peter

Firstly I must say what a stunning job you are making of you boat, it really is a work of art and can't wait to see run. I was just looking at your water pick ups and wonder if I could possibly ask you opinion. As you possibly aware from the forums I am converting a cougar 225 to inboard engine and using a sealed water system with heat exchanger. The engine a 3 litre Mercedes turbo charged diesel with charge cooler and is expected to be 270bhp max. The raw water will first flow though the charge cooler heat exchanger then trough the main engine heat exchanger, the engine has a built in oil cooler heat exchanger connected to the sealed system.

I notice you have used 1.25 inch O/D tube for you water pick ups with probably 1.125 inch ID and you engines produce 725bhp. The inside cross sectional area of your pick ups would equate about 1 inch.

I wonder if you think I will get away with 0.875in I/D which equates to 0.6in Cross sectional area, which is 60% of the size you are using. On the one hand I will be running well under half the horse power and with a diesel which is thermally more efficient, but on the other hand, I will be running a charge cooler too.

In you opinion do you think this size would be OK for my pickup up and run through the whole system.

Look forward to you reply.

Regards David

Hi David,
I think your your proposed pickup pipe size will be fine. I would mount the pickup down the V as low as possible with the rear of the pipe 1/4 to 5/6th lower than the front and also fit a water pressure gage in the pipe before the strainer and adjust the pipe angle until you have got around 1.5 bar at max speed. Very interesting build and i think it should go well and handle nicely with it's low centre of gravity.

Peter

[PerformanceDodge]

Hi Peter

many thanks for your reply, just happen to have the tube and bends in stock. that's set my mind at rest.

Thanks, David

[PerformanceDodge]

Originally Posted by peterunwin

Hi Jon/JW,
The strainers are mounted slightly below the expected water line at rest,i am also incorporating a flushing connection between the full bore ball valve & the strainer so that i can run fresh water through the heat exchangers & headers if we are away from home for any length of time, can also be used to back pressure the pickup to clear blockages.There will also be a 2 bar pressure relief valve to take out any unwanted pressure spikes.

Peter

Hi Peter

Hope you don't mind me asking, what are you using for pressure relief valves on the strainers and would you know where to get them.

Many thanks in advance

David

[peterunwin]

Originally Posted by freddy21

Hi Peter

Hope you don't mind me asking, what are you using for pressure relief valves on the strainers and would you know where to get them.

Many thanks in advance

David

Hi David
The relief valves i used on Cinzano & the Hunton Ilmor are hydraulic check valves made from 316 stainless steel including the specially made springs to give a 2 bar cracking pressure, i will PM you a price tomorrow.

Peter

[peterunwin]

Hi All,
On a recent pre-launch check of Cheetah i found the starboard propshaft a little bit notchy so we abandoned plans for the launch & removed the drive.On stripping the drive & inspecting the parts i found that one bearing was begining to fail causing the bearing spacer to rotate into the path of the gears causing quite a lot of aluminium debris.However catching it early prevented any further damage & the drive is now rebuilt ready for fitting to the boat on Thursday.The only parts used were 1 bearing 1 seal & a few shims.

Peter

[Cookee]

Originally Posted by peterunwin

Hi David
The relief valves i used on Cinzano & the Hunton Ilmor are hydraulic check valves made from 316 stainless steel including the specially made springs to give a 2 bar cracking pressure, i will PM you a price tomorrow.

Peter

Can I get a copy of that PM? We're doing a twin diesel / Arneson setup with water pickups and could do with some relief valves as well!

I would also be interested in what engine mounts you're using if it's not top secret!

Thanks!

[Jon Fuller]

Are you havin a bubble barf?

This boat must be real special!

Originally Posted by Cookee

Can I get a copy of that PM? We're doing a twin diesel / Arneson setup with water pickups and could do with some relief valves as well!

Thanks!

[Cookee]

Originally Posted by Jon Fuller

Are you havin a bubble barf?

This boat must be real special!

Very!

[peterunwin]

Hi All,
I drilled the transom today for the exhaust header drain down and relief valve fittings, also completed the last of the hosing. Next job on the list is to use an old control cable to establish the length and most appropriate route for each cable.

Peter

[peterunwin]

Hi All,
Marked out the rear panel for the exhaust tailpipe cutouts.I am using plastic drainpipe for establishing the length & alignment, haven't decided yet whether to run them the whole length of the swim platform, will experiment tomorrow, the real pipes will be considerably larger in diameter.

Peter

[peterunwin]

Hi All,
Mocked up several styles of tailpipe today but have decided to go with the full length ones with a slash cut.

Peter

[Tom Stone]

could you not have gone through the bathing platform like jeff used to do on the 36's?

[gary mills]

not being funny look at the pipes aqnd the real ones will be bigger,dont think they will fit. i made some for another hunton which were only 2.5 inch dia and they only just fitted these on peters boat will be about 4.5 inch dia

[peterunwin]

Originally Posted by Tom Stone

could you not have gone through the bathing platform like jeff used to do on the 36's?

Hi Tom,
Having engineered through the bathing platform exhausts for the current boat they are extremely difficult to work on & fit, also they have to be made in sections to get them in, some parts are fitted inside the boat some from the outside & then joined. As Gary has also pointed out the real pipes will be way too big to go through the gap without rolling them to an elongated oval & as the starboard engine is a plugin there just isn't enough room to make a round to oval adaptor. Other factors to consider are with staggered engines & a very large belly fuel tank when the boat is at rest with a full tank the bathing platform will be almost parallel to the water, so i wouldn't be able to get enough fall on the pipes also that area is being used for steering transducers & wiring trunking.

Peter

[kitten]

Don't forget the fact that they will look sooooo bling all polished up out there.
Build looks seriously cool, why not take some of it outsideso it can be seen.

[peterunwin]

Originally Posted by kitten

Don't forget the fact that they will look sooooo bling all polished up out there.
Build looks seriously cool, why not take some of it outsideso it can be seen.

Thanks kitten unfortunately the boat is temporarily built into our workshop surrounded by racking & it would be a huge task to take outside, so it will only emerge when transport is booked to bring it to Southampton. Would love to come & see you & John when you start rigging?

Peter