The CG specs are a bit behind the times with respect to fuel
hoses. I'd use nothing but armored EPDM (ethylenePropyleneDiamineMonomer) hosing as its more compatible vs. diesel
fuel. The usage of Copper in the fuel lines promotes fuel degradation. I prefer stainless steel
with at least two 'stress relief' joints to prevent embrittlement due to vibration, etc. In ANY piping system choose double flared connections if possible. The simple and typically found 'compression fitting' should be considered SINGLE
USE only and should be replaced (and the tubing 'trimed back' to undeformed metal) after you re-open them. Compression
fittings deform the copper tube to make a seal and are a notorious site for air leakage.
To prevent 'foam-out' when filling the tank, consider to relocate the inlet fill hose so that it discharges onto the inside SIDE wall of the tank - not the middle. Also KNOW how much fuel you need to put into the tank and watch the delivery
meter. A bubble trap can be arranged to break foam-out bubbles .... simply filling a section of the vent line with small bundle of 'capillary' tubes - the small tubes burst the bubbles but permit
As regards the 250 rpm
difference that you see, consider that most gages on boats are not calibrated and simply the difference you observe may be only a 'gage' fault. However and in addition to the other suggestions of injector, governor and high pressure pump overhaul
, also consider that if you've been using degraded and contaminated fuel that there is a possibility that the exhaust
system may be loaded with soot and that there is high exhaust
manifold back pressure due to the carbon fouling --- may reduce output rpm
- and you may not necessiarily see any smoke, etc. issuing out the end of the exhaust stack (this is called 'coking'). A similar exhaust blockage condition can be encountered at the area of the water
; as where the cooling
water is injected to the exhaust, the sudden high temperatures encountered by the cooling
water may cause calcium carbonate (rocks!) formation accumulation which also partly blocks the exhaust circuit and causes back pressure to the cylinders - hence power loss. Carbonate (precipitation) build-up is easily remedied by 'pickeling' the raw water
circuit with an acid or (better) organic boiler descaling compound - usually performed as routine mainentance, especially when and in addition to cleaning
out the heat exchanger
. I wouldnt disassemble an exhaust system to simply look for blockage; but, if and when you replace the exhaust system next time consider to add a gage port so that you can monitor
the exhaust pressure .... just a simple 'boss' to which you can add a gage when needed to check - the gage only installed when checking, otherwise removed.
For any engine, its best to establish a 'base-line' of operating data so that you have something to compare later on when you perceive something is failing.
At a 'designated' or specific rpm:
Gallons per minute of output cooling water (stopwatch and bucket at exhaust outlet).
Temperatures of inlet and outlet sides of heat exchanger
.... you're establishing 'terminal differences'.
Exhaust manifold pressure.
Exhaust cooling raw water
pressure (before injection elbow) - shows impeller 'slip' and also if water injection elbow
Vacuum gages on fuel delivery
system to monitor
For tank diptubes, most keep the diptube off the bottom to prevent suction of accumulated water and large debris. An alternative to be sure that there is no water in the tank bottom (to prevent bacterial and fungal growth) simply run the dip tube all the way to bottom and place an EMPTY filter housing in the FIRST postion after the tank in the fuel delivery line. The water will separate by gravity from the oil
in the empty filter housing ... simply and routinely drain off the water from the bottom of the 'empty' housing with a 'cock-valve' at the bottom of the housing occasionally to prevent the water from challenging the filters, and travelling further down stream. There is no way to easily drain water from bottom of a marine fuel tank
, its easy to drain such a 'water-knock-out' pot.
If your normal source of fuel is unreliable and occasionally also delivers water (either emulsified or free water), consider to purchase
a large fuel filter
that has an added water absorbing starch (HydroxyMethylCellulose) - be sure to routinely monitor such a filter with a gage so that you can see when to change-out.
I can email
you a schematic of fairly 'upgraded' fuel delivery system (110 gal.) that I have on my boat that also includes an onboard recirculation polishing system and a lock-in/lock-out gravity feed day tank to ensure an extremely reliable source of available fuel for 'emergencies'. Most boat fuel systems are quite 'primitive' and what I have would probably be considered 'state of the art'. email
me @ RhmpL33ATattDOTnet if you want to view a 'serious' fuel system.
Hope this helps.