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Old 17 November 2008, 16:04   #11
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That screw you pointed to is the rack stop, this effectively adjusts the fuel delivery, when adjusting by allowing the fuel rack to open futher. this will not affect the maximum governed RPM of the engine, however if fueling is very lean obviously the load will stop the engine revving up to governed speed.

Really you need to check the valve clearences, though in my opinion its unlikley to be a problem, and intake exhaust for blockages then assuming ther fuel filters are clear and there are no other problems with leaking pipework make sure the engine can reach ~300 rpm more than the expected max on load speed on the throttle stop screw, then start fiddling around with this screw until you just get a little whif of black smoke under aceleration.
It will also be worth checking if there is a compensator device on the pump, and if it works, this will increace fuel with boost.(i cant see one)
diesels without a compensator can smoke fairly heavily when accelerating while the turbo plays catch up. it should be clean once the turbo spools up.

If you are unsure if you have over fuelled fit an exhaust gas pyrometer. do a google on EGTs I would also fit a boost gauge so i could see whats going on.
When pumps come from calibration they can be wrong, yours could be set to fuel a non turbo for example!
I am unsure why your rpm dips, maybe because of the hull shape and bite the prop has? or some anomaly with the fuel delivery, i think it requires more fiddling
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Old 17 November 2008, 17:05   #12
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Cheers for that, im not the one doing the fiddling thats Andy my brother I just do the steering (Im a decky afterall!)

the prop has a fair bite, this is a pic from when we first got the boat



and hull profile



Hull has been cleaned since these photos

T the posn where it is has been fiddled to just now theres alot of black reek when accelerating but once the turbo spools it runs clear. There is a boost gauge fitted, once the turbo spools it hits a max of half a bar then once the boat is up to speed it drops to 0.4 of a bar

As you say more fiddling required!!!

New exhaust hose is on order so will be removing the old exhaust and checking for any blockages due to growth etc, the valve clearances will be checked Fri / Sat depending on weather as boat is outside (I think Mermaid quoted 0.18 for inlets and exhausts) and turbo will be removed for inspection and overhaul (got a rebuild kit on the way). We have also got a full set of water and boost hoses so these will be changed out also.
Charge cooler has already been taken off, cleaned and painted
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Old 17 November 2008, 18:04   #13
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I wouldnt touch the turbo yet, its unlikely problem unless its obviously lunched if you visibly inspect the compressor and turbine, if you disturb it it needs balancing or the result could be catastrophic.
I think you found the problem....if the boost is falling once the boat is up to speed then its because the fuel is reducing. this is probably because the no load speed is set too low.
the phenomenon is called govenor run out, if the no load speed of the engine is set to say 2800RPM which would be in the right area for the engine the fuel rack will stay fully open until around 2300-2400 then it starts to shut off.
so if you want the full load speed of the engine to be 2800 you may need to adjust the throttle stop to allow a bit more movement.
theres two screws on the throttle arm one for tickover and one for max rpm.
try a tweak here, it may get those last few hundered rpm you need to get the extra speed.
still at a loss why the rpms dip though!
It sounds like he govenor RPM and the Rack stop were both set a bit cautiously.
If you have black smoke under aceleration, and .5 bar boost then that may well be all its got to give in terms of aceleration without risking high EGTs and melted turbine blades.
Its worth checking what the boost is meant to be, if its low then it could be the turbo, does it have a wastegate that could be sticking open and reducing boost?
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Old 17 November 2008, 18:16   #14
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One other thing are you sure its a 204HP? i have been looking at mermaid engines on the website, and i recognise the engine as a ford tractor engine,
I am familiar with the 4 and 6 cylinder versions, and the six turbos arent even 200HP i thought the 4 cylinders were about 150hp. Unless they run a lot more boost than the six?
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Old 17 November 2008, 19:06   #15
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Cheers for all the great info, will read a couple more times to digest.

http://www.mermaid-marine.co.uk/PDF/...TurboFour3.pdf

We bought the boat through Babcock Disposals advertised as 204HP, whilst chatting to mermaid they told us that the last of the Turbo 4 units for the MOD were uprated to 200BHP with uprated internals. Im going up to the boat tomorrow to get some serial nos from the turbo and engine and will be able to confirm (or deny) what power rating the boat is.
Will also be talking to Turbo technics to see if they can offer advice on a Hybrid turbo to aid spool if we hit a dead end.

On initial sniffing about the turbo there apears to be no wastegate fitted
they arnt the best pics, but will try get some more whilst up at the boat tomorrow





Many thanks

Graeme
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Old 18 November 2008, 03:58   #16
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Grame, for reference Old Spice with a 200 hp Mermaid used to get over 1 bar of boost from the turbo at speed. Turbo was noticable from 1800 revs and smoked really quite badly until then. Max revs was 2800 in gear with 21 and 22 inch props and light loaded. The P22 manual is here is you want it:

http://www.polar-ribs.co.uk/


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Old 18 November 2008, 04:25   #17
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Hi,
as there is no wastegate on the turbo,or a compensator or the pump then you will have to put up with smoke before the turbo spools up.
If extra fuel on the screw you already played with dont improve things and increace boost, then, as pete 7 suggests youre low on boost it may be worth checking the exhaust for blockages and the turbo for damage and its the correct unit.
did you spill time the engine when you changed the pump? if the timing isnt spot on that wont help.
its still worth trying more fuel on that screw, it may make the turbo spool quicker and actually reduce the smoke once it gets going.
IMO the turbo should be creating boost from quite low rpm.

as you say a hybrid turbo may improve bottom end but may jigger the top end, a wastegate is the way to go with a smaller turbo to reduce lag.

or fit a nice 6 cylinder yanmar
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Old 18 November 2008, 09:03   #18
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Screw the 6cyl yanmar
V8 Tigershark diesel 400HP - 948lbs torque
http://allmarinediesel.com/Tigershark%20Page.htm

Will update you all at the weekend once we have been back up to the boat

Graeme
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Old 18 November 2008, 09:11   #19
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In addition to the exhaust hose, I would have a look at the route air takes from the turbo to finally entering the clys. Since the Mermaid has an intercooler and several pipes any one of these could either leak or have a pacial blockage. The ali parts are easy enough to take part and stuff in a dishwasher to get clean

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Old 18 November 2008, 09:25   #20
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Quote:
Originally Posted by G.Mac View Post
V8 Tigershark diesel 400HP - 948lbs torque

They really are a piece of crap. A pal of mine had one installed by the local agent in his boat, but it didn't perform as expected, been back to marine diesel in Sweden a few times, and they can't make it work. Last time back they put it on the dyno, and admitted it was only making 230 ish hp! They're unable to sort it, and having spoken to numerous people who've tried other motors from them, it seems to be a common problem.
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