stefan_r
Well-Known Member
- Joined
- 16 May 2001
- Messages
- 753
- Location
- Southampton & Greece (Chios)
So, picture the moment...running the boat for a first good outing after a long winter. Have already done a couple of hours to turn over the engines and run all systems after wintering ashore.
Significant change for 2009: had a few inches of pitch on the props over winter as the boat is sensitive to trim/load/prop pitch/fouling. HUGE difference - runs sweetly now!!! In 2008 had engines totally reconditioned, fuel pumps replaced, cylinders roughed...the works. Still suffered with performance being a bit off "new"....the boat is a 1991 model Mochi Craft 46' flybridge with twin 680hp MAN D2848LXE, runs great....but needed a spruce up after 18 years of crappy marine diesel.
Sunday afternoon run from the marina an hour down the road, drop hook, lunch (no booze) then run back with a couple of friends on board.
Run down perfect. Getting just shy of 30 knots and know the boat is under(or is it over?) propped and with a bit of hammer and an inch or two off the props 30k can be cracked with the right fuel load (almost 4,000L on board including "special" reserve tanks under fwd berths) more usual fuel load 2,000L-ish.
Run home equally as good...but about a mile out of port performance drops off.
Can no longer rev to 2,300RPM.
Top end now early 20 knots.
Engines smoking as-if under heavy load if revved to max...previously spooled up to max no probs.
Much scratching of heads...
Performance seems to be back to "pre prop recondition".
Easy answer: the heavy fuel load needs a manual swap from under fwd berths to rear-mounted fuel tank, therefore trim is "off" and therefore performance has taken a hit. This has happened recently because I have been for a run and burnt just enough diesel in rear main tank to cause a change in trim as boat now nose heavy.
Fine.
Sluggish response trying to reverse into berth....bit of an Easterly blowing, bit unusual, so it's probably wind then.
Eventually manage to moor up...though a pain in the arse because of wind/turn rate/ reverse speed/whatever....or maybe just my cackhandedness!!
Moored against jetty...hmmm exhaust sounds funny...."bubbling" as if underwater as opposed to usual burble.
Look over side...PANIC - water above antifouling!!!!!!!!!!
Open engine hatch PANIC water over checkerplate though thankfully under batteries/engines/genny etc.
Switch everything off, listen to bilge pumps working overtime, start manual pumping.
Monitor water level.
Water level drops after toooooooooo long.....sweats start to subside, though it's 32 degrees outside and nearer 60 in the engine room so sweat is expected!
Stop pumping.
Water level unchanged.
Look for holes...nothing.
Pump out until normal level.
Leave for a while....no change.
Start port engine WHOOSH (680hp MAN). Gearbox raw water cooling pipe hanging loose and nicely filling boat. The engine alone can deliver 430 litres per minute of cooling water at full chat. Gearbox feed is smaller.....but.
So: lessons learned:
1. install repeater for "bilge pump working warning light" on flybridge. Only on lower helm and in the Med I never drive inside apart from at night.
2. don't assume the easy option. I thought fuel imbalance (thus trim) and the need to move 2 tonnes of diesel from reserve into rear-mounted main tanks caused performance drop whereas it was carrying maybe 3 tonnes extra weight in seawater!!!!! If something changes check all systems/are working. A quick glance at the engines bay a mile out when performance dropped off would have told me something was wrong. When I got previously unseen black smoke again a quick look at the engine bay would have indicated high water levels.
3. spend as much as you can afford on bilge pumps. I replaced the manufacturer's standard with run dry Johnsons AND an extra centrifugal pump a couple of years ago....brilliant. Never faltered, never clogged despite the crap that was washing around. Worth their weight in gold. Bilge pumpps...go BIG!
4. checking ALL hoses and fittings EVERY trip is a pain in the arse but f/forums/images/graemlins/mad.gifk me it would have been a life-saver....especially if we were 5 miles out of port when performance dropped (and I had a few thousand litres of extra weight/water on board) and not just a mile...creeping into port by luck. Another half hour would have meant water over batteries and dead in water, with only manual pumping an option.
5. know your boat and where all the pipes and hoses come/go...it was quite easy once it was clear the problem was not a hole or broken skin fitting to trace water cooling circuit (complex for me as raw goes to engine, gearbox, vee-drive) and seperate feeds for genny, sternglands etc...not to mention all the other thru hull fitings for water in - toilets, wash pump and various senders/logs etc
Significant change for 2009: had a few inches of pitch on the props over winter as the boat is sensitive to trim/load/prop pitch/fouling. HUGE difference - runs sweetly now!!! In 2008 had engines totally reconditioned, fuel pumps replaced, cylinders roughed...the works. Still suffered with performance being a bit off "new"....the boat is a 1991 model Mochi Craft 46' flybridge with twin 680hp MAN D2848LXE, runs great....but needed a spruce up after 18 years of crappy marine diesel.
Sunday afternoon run from the marina an hour down the road, drop hook, lunch (no booze) then run back with a couple of friends on board.
Run down perfect. Getting just shy of 30 knots and know the boat is under(or is it over?) propped and with a bit of hammer and an inch or two off the props 30k can be cracked with the right fuel load (almost 4,000L on board including "special" reserve tanks under fwd berths) more usual fuel load 2,000L-ish.
Run home equally as good...but about a mile out of port performance drops off.
Can no longer rev to 2,300RPM.
Top end now early 20 knots.
Engines smoking as-if under heavy load if revved to max...previously spooled up to max no probs.
Much scratching of heads...
Performance seems to be back to "pre prop recondition".
Easy answer: the heavy fuel load needs a manual swap from under fwd berths to rear-mounted fuel tank, therefore trim is "off" and therefore performance has taken a hit. This has happened recently because I have been for a run and burnt just enough diesel in rear main tank to cause a change in trim as boat now nose heavy.
Fine.
Sluggish response trying to reverse into berth....bit of an Easterly blowing, bit unusual, so it's probably wind then.
Eventually manage to moor up...though a pain in the arse because of wind/turn rate/ reverse speed/whatever....or maybe just my cackhandedness!!
Moored against jetty...hmmm exhaust sounds funny...."bubbling" as if underwater as opposed to usual burble.
Look over side...PANIC - water above antifouling!!!!!!!!!!
Open engine hatch PANIC water over checkerplate though thankfully under batteries/engines/genny etc.
Switch everything off, listen to bilge pumps working overtime, start manual pumping.
Monitor water level.
Water level drops after toooooooooo long.....sweats start to subside, though it's 32 degrees outside and nearer 60 in the engine room so sweat is expected!
Stop pumping.
Water level unchanged.
Look for holes...nothing.
Pump out until normal level.
Leave for a while....no change.
Start port engine WHOOSH (680hp MAN). Gearbox raw water cooling pipe hanging loose and nicely filling boat. The engine alone can deliver 430 litres per minute of cooling water at full chat. Gearbox feed is smaller.....but.
So: lessons learned:
1. install repeater for "bilge pump working warning light" on flybridge. Only on lower helm and in the Med I never drive inside apart from at night.
2. don't assume the easy option. I thought fuel imbalance (thus trim) and the need to move 2 tonnes of diesel from reserve into rear-mounted main tanks caused performance drop whereas it was carrying maybe 3 tonnes extra weight in seawater!!!!! If something changes check all systems/are working. A quick glance at the engines bay a mile out when performance dropped off would have told me something was wrong. When I got previously unseen black smoke again a quick look at the engine bay would have indicated high water levels.
3. spend as much as you can afford on bilge pumps. I replaced the manufacturer's standard with run dry Johnsons AND an extra centrifugal pump a couple of years ago....brilliant. Never faltered, never clogged despite the crap that was washing around. Worth their weight in gold. Bilge pumpps...go BIG!
4. checking ALL hoses and fittings EVERY trip is a pain in the arse but f/forums/images/graemlins/mad.gifk me it would have been a life-saver....especially if we were 5 miles out of port when performance dropped (and I had a few thousand litres of extra weight/water on board) and not just a mile...creeping into port by luck. Another half hour would have meant water over batteries and dead in water, with only manual pumping an option.
5. know your boat and where all the pipes and hoses come/go...it was quite easy once it was clear the problem was not a hole or broken skin fitting to trace water cooling circuit (complex for me as raw goes to engine, gearbox, vee-drive) and seperate feeds for genny, sternglands etc...not to mention all the other thru hull fitings for water in - toilets, wash pump and various senders/logs etc
