Our Mermaid Mariner

The engine was installed in early 2008 and has been very reliable from the very first turn of the key, through a North Sea crossing and then on through France and Belgium. Our only concern is a slightly high oil consumption which Mermaid state is normal for this heavy diesel engine but which we have to keep a check on. We think we may not be running it hard enough in the canals and this may have lead to slight glazing of the bores. We find that Waterdog is difficult to steer at anything over 1600 revs and we can generally do our top speed for the smaller canals at 1100 to 1200 revs. That is using only about 70 HP of the 135 available. We did only 50 hours of running before setting off down the North Sea to Dunkerque but I did change the oil before that voyage.

engine side view

The engine looks great in white but we basically chose that colour so that I could see any oil or diesel leaks. We did have one leak on the injection pump and I could see the pink stain (red diesel was legel then) as it seeped from the pump, a tightening of a nut sorted that out though. We were very keen to get a non-turbo engine that was fairly low revved and this was one of three that we could buy with those guidelines. There was also the Perkins and the Doosan, but we thought the ford would be easier to find spares for since it is a marinised common truck engine.

We had the engine solid mounted to the engine bed which meant the engineers at MMS in Hull had to make the alignment to the short propellor shaft very accurate. This initially caused a problem as the flnge on the PRM showed more miss-alignment than the engine manual said was acceptable. PRM sent 2 engineers up immediately with a spare flange and changed it to give better but not perfect results. It was eventually set up with just 4/1000" miss-alignment and seems pretty good. The soid mount engine probably gives more vibration and noise through the boat than a flexible mounted engine but there seems less to go wrong and Waterdog is big enough and heavy enough to get away with it.

We have a dry exhaust and cooling water outlet that is just below the deck level. This is a hang over from the commercial days of Waterdog when the freeboard could be anything from near zero to 5 feet. We decided the dry exhaust was a simpler way to go than wet and would fit with what was there already.

 

engine top view

The PRM 500 gearbox was chosen because it would be easily fitted with hydraulic power take off and also the spec describes its multi plate clutch which would be capable of taking the mariners rated HP from full ahead to full astern. Not something we would like to test though.

We keep a tally of fuel used against hours and km run. This helps us plan ahead for how much fuel we need for each trip and also helps us spot problems The highest fuel consumption we have experienced was when doing 1700 revs for the North Sea crossing and using about 11 litres and hour at 6 to 7 knots. As a comparisen we can generally do 4 litres an hour at 4 knots in the canals. On smal canals we are slowed by interaction with the canal bd and banks and our speed drops to 3 knots whatever engine revs we use, if we increase revs above 1000 on a small canal we just use more fuel and don't go faster.

The table to the right shows our fuel figures based on site gauge readings over about 1100 km. This improved after dry docking in 2011 as Waterdog had a clean painted hull but we can generally look at 4 litres per hour equating to about 1.5km per litre.
revs
litrs /hour
800
1.5
900
2.5
1000
3.96
1100
4.12
1200
4.30
1300
5.10
1400
5.40
1500
7.00
1600
9.00
1700
11.00
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