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Old 09-11-2016, 05:36 AM   #21
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"You should never operate a generator continuously at greater than 70% load,"

Larger sets (hospital in a desert) are set to work at 90% load for lowest fuel bill and longest life.

On larger cruise ships a set will be taken off line at 70% so the other running units see a better more efficient operation.
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Old 09-11-2016, 06:34 AM   #22
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"You should never operate a generator continuously at greater than 70% load,"

Larger sets (hospital in a desert) are set to work at 90% load for lowest fuel bill and longest life.

On larger cruise ships a set will be taken off line at 70% so the other running units see a better more efficient operation.
I agree with this. Back when I was doing load calculations, and later when I was reviewing and approving them, the objective was to have the generator running at 80% - 90% as much of the time as possible. It could be tough to do with highly variable loads such as AC. Most vessels I was involved with had two generators and either paralleling equipment or split buss set ups.

BTW I'm feeling a bit foolish about repeating what I was told about the propulsion engine FW pump "weakening". I immediately though of RW and oil pumps, both of which are positive displacement and therefore can weaken with impeller wear. I don't see anything sinister here as a couple of posters suggested. I'm getting the information third hand through at least one not too technical person. There was evidence of water leakage under the pump. I'm sure the captain went down to investigate the slight temperature rise, found the pump seals leaking, and sent it out for rebuild. That is taking longer than expected so something was wrong. However, agree with posts above that whatever was causing the slight temperature rise will probably still be there when the rebuilt pump is installed.

The Captain is reported to be a gauge watcher and the engine was shut down immediately upon seeing the temperature start to rise and then only used again for a couple minutes of docking. The alarm never went off. It's also possible that the pump failed entirely and his careful monitoring saved an overheat event. I hope to talk to him when he becomes available and will report on that and the machinery survey.
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Old 09-11-2016, 07:19 AM   #23
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Old 09-11-2016, 07:26 AM   #24
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Old 12-26-2017, 03:40 PM   #25
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Gulfstar 43 Mark II purchase

I have owned a 1975 Gulfstar Mark II since 2000. I have replaced the port engine water pump with parts from Perkins, 165.00. The starboard engine spins in the opposite direction and water pump is different and not available. Perkins recommended a local company the rebuilt it for 125.00. Both work great. I found a thermostat at Baxters auto Parts and all cooling issues were resolved.

My engines have 3,100 hours. I really like the boat. It slides through the water and burns around 2 gallons an hour or less.

I have a ONAN 7.7 MJDE(?) that is leaking oil (quart or more in 2-3 hours). Cant see where it is coming from but thinking it is the oil pan or generator side gasket. Does anyone have any experience with this?

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Old 12-26-2017, 08:07 PM   #26
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I have a ONAN 7.7 MJDE(?) that is leaking oil (quart or more in 2-3 hours). Cant see where it is coming from but thinking it is the oil pan or generator side gasket. Does anyone have any experience with this?

Steve
Probably the rear main seal if it's dripping near the back of the pan or where the generator attaches. If there is blowby, it often pushes oil past the seal. Depends on the seal type and age.
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Old 12-26-2017, 08:12 PM   #27
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I have a ONAN 7.7 MJDE(?) that is leaking oil (quart or more in 2-3 hours). Cant see where it is coming from but thinking it is the oil pan or generator side gasket. Does anyone have any experience with this?

Steve
Welcome aboard. That is a huge leak for a generator or main engine. Remove all of the sound enclosure panels. Get a dozen oil sorbent pads and roll of paper towels and wipe down everything bone dry. Line the drip pan with new pads and start it up. With that leak rate drops will appear shortly on the pads. Get a good flashlight and follow the oil trail.
Post a few pictures when you can.
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Old 12-27-2017, 01:10 PM   #28
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Thank you for your prompt response. I have cleaned the pan, several times, and noticed a drip coming down the case between the engine and generator. Couldn't get a clean look at it as there is a fuel filter in the way. The scary part is how to get to the seal or gasket. It's all big dark and heavy.

I'm not going to be on the boat for a few weeks but will post results or more information requests. Thank you, Steve
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Old 12-27-2017, 01:16 PM   #29
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Thank you for your response. Having seen a drip on the case between the engine and generator I'm thinking the same thing. Not sure I understand the blowby concept. Is there an escape route for the engine oil if the pressure is to great? Why/How would the pressure get to push the oil out. Makes sense as there was a lot of oil being pushed. I'm assuming the seal is as old as the unit.
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Old 12-27-2017, 03:22 PM   #30
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Having seen a drip on the case between the engine and generator I'm thinking the same thing. Not sure I understand the blowby concept. Is there an escape route for the engine oil if the pressure is to great? Why/How would the pressure get to push the oil out. Makes sense as there was a lot of oil being pushed. I'm assuming the seal is as old as the unit.
When cylinders and rings get worn (or with glazed cylinders) some of the combustion gases get past the rings into the crankcase, increasing the pressure. The engine crankcase breather is designed for normal operation and usually doesn't allow enough pressure to escape. So the increased pressure pushes against the seals. The easiest escape for large volumes of oil is the rear main seal because of it's proximity to a bearing using pressurized oil. Rubber seals get stiff and brittle as they age and no longer hold tightly to the crank. In older engines with rope type seals (looks similar to shaft packing) becomes compressed and no longer pushes against the crank.
To repair, the generator and flywheel need to be removed. In some engines the pan and rear bearing cap need to be removed. And some older engines need the crank removed to replace the top half of the seal. I don't know your engine, but probably the seal is one piece and replaceable after the flywheel is removed.
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