markpierce
Master and Commander
- Joined
- Sep 25, 2010
- Messages
- 12,557
- Location
- USA
- Vessel Name
- Carquinez Coot
- Vessel Make
- penultimate Seahorse Marine Coot hull #6
Smaller engines give the mechanic more room in the engine room/compartment.
This is one of the main reasons noisemakers are of two different sizes on larger boats.
The night load is minor , and would be very hard on the day unit.
This is done even tho 2 identical noisemakers would offer easier servicing and a source of spare parts .
Eric, you have it figured out. Heat and cool oil via coolant with a plate heat exchanger that is mounted on side of engine. The oil always seems to be at least 10F degrees hotter than coolant at low loads and about 15 to 20F at higher loads.
At my low (1500 RPM) to normal (1750 RPM) cruising loads I don't find (measured with IR gun) oil temperatures below 185F once engines have warmed up.
Sunchaser,
This makes no sense to me at all. The coolant is artificially kept higher than it would normally be by the thermostat. The oil has no thermostat and most of the time it sits in the bottom of the sheet metal oil pan w large area exposed to ambient cool air. I don't think I do "get it".
Sunchaser,
This makes no sense to me at all. The coolant is artificially kept higher than it would normally be by the thermostat. The oil has no thermostat and most of the time it sits in the bottom of the sheet metal oil pan w large area exposed to ambient cool air. I don't think I do "get it".
Coolant to oil heat exchangers are really elegant. At low power with thermostat closed, coolant is recirced and the oil HX is on the discharge of the water pump, between that and the block. As engine warms up, it does actually put some heat into the oil. Running at high load, the thermostat is open and lots of coolant is going through the coolant HX. This drops the coolant temp coming out of the water pump, so tends to cool the oil. And at high load there is much more heat going into the oil, so this is where you want cooling and you get it.
With the oil hx you get oil temps like 190f at light load, 210 at high load, or thereabouts. Pretty tight range, really.
A couple thoughts:
2 pole generators are much more prone to glazing due to running at constant high speed with light loads. Generators running at 3600 rpm (60Hz) are more at risk than the generators running at 50 Hz (3000 rpm).
Larger generators are often 4 pole running at 1500 or 1800 rpm. There are less glazing issues with these.
Even the small generators we have are at 1800 rpm. Most modern generators are. We have Northern Lights, Kohler, and Onan from 7.5 kw to 99 kw and all are at 1800 rpm.
Panda lovers will squeel at this! Your 1800 units become 1500 at 50 hz. BTW, bigger gensets than yours drop down from 1800 RPM while at 60 hz.