Nanni 4.390 saga continues (low power low speed)

James066 said:
I’ve got a nanni 4.380 and my maximum revs are suddenly 2900 making speed 12knots instead of 3600 and up to 20knts - I’ve done all the checks recommended on this thread but nothing is solving the problem. I’ve booked in for lift out but am doubtful that light fouling I can observe at low tide (drying harbour) would cause such a massive drop in performance. Any ideas?
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Single or twin engines? Shafts or legs?
 
Yeah it will go to normal max revs 3600 out of gear without issue (if only very briefly for fear of doing more harm than good) . Prop shaft turning as normal - real head scratcher this one
 
Only other thing I can think of would be the linkage setup.
Do you still get full throttle position at the pump when the button is out on the morse control and pushed to full position (in gear and throttle)
as opposed to when the button is in (just revving the engine without being in gear) ? Maybe the linkage adjustment is out?
 
Check these
Waist gate stuck open . Undo the linkage and see if the waist gate moves freely.
Dismantle the racor fuel filter completely to check for diesel bug (just don’t change the filter)
Check the pick up pipe in the fuel tank as some tanks have a gauze on the bottom of the fuel tank pick up pipe that clog up with diesel bug.

is the hull really clean or just look it . Jet wash it to make sure the growth is not the issue as your be surprised how little growth can slow you down.
 
jamie langstone said:
Check these
Waist gate stuck open . Undo the linkage and see if the waist gate moves freely.
Dismantle the racor fuel filter completely to check for diesel bug (just don’t change the filter)
Check the pick up pipe in the fuel tank as some tanks have a gauze on the bottom of the fuel tank pick up pipe that clog up with diesel bug.

is the hull really clean or just look it . Jet wash it to make sure the growth is not the issue as your be surprised how little growth can slow you down.
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Thanks for the suggestions - I will be lifting her next week for jet wash and antifoul - in the meantime I’ll try the waste gate as I’ve only tried moving it whilst the linkage is attached. Pretty sure it’s not related to the hull but will get that eliminated and see.
 
From all I learned during my saga I concluded that it was lack of fuel (because the hull had been "cleaned" already) as it may max out when not under load but would be starved when under full load. You can measure the fuel pressure with the right kit at the pump to be sure. As it turned out mine was due to hull fouling after hours of investigation. I fitted a fuel pre filter with glass bowl right out of the tank to see if any contamination. Good luck.
 
freddyuk said:
From all I learned during my saga I concluded that it was lack of fuel (because the hull had been "cleaned" already) as it may max out when not under load but would be starved when under full load. You can measure the fuel pressure with the right kit at the pump to be sure. As it turned out mine was due to hull fouling after hours of investigation. I fitted a fuel pre filter with glass bowl right out of the tank to see if any contamination. Good luck.
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I’ve cleaned the hull and antifouled - speed is up now to 15knts but the revs max out at 2900 not 3600 - I have a prefilter (racor) - I’m guessing it’s fuel related possibly governor issue but don’t know. Still scratching my head with this one
 
Hi
jamie langstone said:
Dismantle all the fuel lines right back to the pick up pipe in the tank and check for blockages . Have you had the turbo checked .
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Hi, yeah we have today tried running from a deck tank and had the same issue. Exhaust end of the turbo was clean and waste gate is free. I’m trying to find out if there are boost pressure data available for the engine - I’ll then install a boost gauge and check that
 
Actually a modest boost, but what you'd look for. Should be checked under load to be meaningful. Make notes of the rpm : boost relation.

Mine are making a notable whistle when building boost.

This vid from 3:45 to 3:55 shows a gauge reading (Toyota Prado but same engine)
 
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Mine is doing the same now..
I did fit a Snapp filter which should be ok but might be impeding the flow of diesel.
I didn't check the waste gate yet. She is down to 15 knots full throttle now :-(
 
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