The boat's generator is a 1990 8KW Onan Diesel generator, which had failed long before I bought the boat. The previous owner had made a serious attempt to get the generator working again, but finally gave up in the typical frustration of "expert generator mechanics" swapping parts, spending excessive amounts of money, and ended up with a result that was worse than the original problem...
The survey reported that the generator would start, but would not continue to run unless the stop solenoid was held open.
1990 Onan Model#8MDKDB 1C
Rated at 8 KW at 1800 RPM's and 60 Hertz
Rated at 66.7 amps.
Kabota 3 Cylinder motor.
The survey reported that the hours (~100) on the generator hour meter were not correct.
Rated .8 gal/hour at full load (as per manual)
Filters:
Fuel Filter
Onan 149-1914-04
Donaldson P551744
Carquest 86426
(Get Racor number from previous filter - can't see currently...)
Oil Filter
Onan 185-2123
Fram PH3593A
Fleetguard L3462
Water Pump:
Major Repair Kit for Oberdorfer Pumps 202M-11, Onan 132-0277", $127.19 on Amazon (includes seals, gaskets, and impeller)
12-9-22
Linn from Advanced Marine arrived to diagnose and repair the generator. First date was a very brief diagnosis - which was surprisingly positive. Linn confirmed what the survey had said: He was able to manually override the fuel stop solenoid (hold it open) and get the generator to start and run. Generator would immediately shut down after starting if the solenoid was not held open. Linn also verified that once running, voltage was generated.
Observations included:
New control board, new fuel solenoid, new oil pressure sensor installed.
Remote panel harness had been disconnected (some generators sense his, and will shut down without the remote panel unless a jumper is connected - this does not appear to be the case with the Onan).
Harness had blown 30A fuse. (Replacing the fuse did not help anything.)
Water pump was weeping - needs to be replaced / rebuilt.
Saltwater is in the bottom of the tray. This may be coming from cooling system or heat exchanger?
1-4-23
Linn from Advanced Marine returned. CB-12 (emergency stop circuit breaker) seems to be kicking in within a few seconds of start. Linn checked all the sensors feeding the shutdown relay. They all appear to be functioning properly.
1-27-23
Linn returned. Replaced CB-12 circuit breaker (I had ordered a replacement from Elite Diesel, ~$46). Didn't help.
2-2-23
Paid Advanced Marine $649.50. Generator still does not run. Remote harness is not connected. No understanding of why control board is tripping CB-12 shutdown circuit breaker.
2-17-23
Flight Systems (manufacturer of the replacement generator control board) reorted that the board passed all their system tests. Board returned UPS.
Check: The survey noted that the Generator battery switch was secured to the starboard battery box. ?? Check this! Yes - there is a battery switch next to the starboard battery box. It is currently not wired to anything.
2-19-24
Replaced generator battery with AGM (Walmart). Tried starting, no further success. More attempts resulted in generator no longer even turning over (bad starter?) [Continued failed testing resulted in burned up starter.]
8-18-24
John Allison assisted. Generator starter was determined to be dead at this point (burned out due to attempted starts with low battery, exacerbated by long cables?).
8-25-24
Replaced starter. John Allison continued to assist. Primed fuel, verified fuel pump worked. Determined that fuel pump and solenoid were both wired together. Fuel pump and solenoid shut down as soon as generator started (and start button released).
9-1-24
John Allison over to observe and assist with further testing. Simple wire harness with switch to jumper Batt to fuel solenoid and fuel pump wired in. With switch "on", fuel pump and solenoid were jumpered to run. Generator started easily. Switch turned off (batt jumper connection removed) as little as 2 sec after start - generator continued to run until killed with Stop switch.
15A AC plug wired to generator. Polarity checked. With generator running, voltage was about 112VAC. Tested generator under load by connecting Vissani 5000BTU. Started and ran without any load issues on generator.
Note that raw water pump is leaking badly, and needs to be replaced or rebuilt.
9-7-24
More testing with bypass wiring.
AC input at A11-K15 pins is good, but slow showing up. Power doesn't seem to show up until after generater has started and come up to speed.
Checked voltage on battery as generator was running. Battery voltage was very slowly climbing (.1V increase every 20 sec or so...). So generator does appear to charge the battery (if allowed to run for a while).
Water pump was leaking a LOT. Generator tray was about full of water. (later pumped out with shop vac)
Tried holding start switch on long enough for gen to stay running - that didn't work. (Trying to remember - but I think the control circuit shut down the starter, and then the fuel pump and solenoid.)
Gen only ran with bypass switch providing 12V power to fuel solenoid and pump during start. Switch could be turned off as short as 1sec after generator started, but had to be on for slightly longer than starter switch.
9/15/24
John Allison rebuilt the water pump (I got to help). I removed the water pump Saturday. We took it over to John's workshop, and replaced parts from the "Major Repair Kit for Oberdorfer Pumps 202M-11, Onan 132-0277", $127.19 on Amazon. Kit included seals, bearings, gaskets, snap rings, new screws and impeller.
The pump had 4 screws that secured it to the motor. One was visible. Had to remove the actuator for the fuel solenoid, remove the fuel solenoid, then access the 4 screws. One was visible, 3 were mostly blind... Different short, medium, and short/med combined socket extensions required to remove the screws. Lower right screw was longer than the rest. Pump re-assembled with new parts (old shaft, but everything else inside was new), and re-installed. Installation was a "challenge", due to (lack of access), and not being able to see screws (but mostly lack of being able to reach screws easily).
Used switch wire harness to override wiring - and generator started without any issues, and pumped water. Unfortunately, generator is still leaking a lot of water into the generator pan. Will need to track down where that is coming from (upper and lower raw water hoses both VERY soft and need to be replaced - possibly one of those is leaking, but probably leak is coming from somewhere else in the cooling system / heat exchanger).
During the week (9/11/24) - wired up delay circuit to replace switch override. Will need to figure out where to place the circuit and relay.
10/27/24 - Replaced upper and lower hoses on raw water pump.
11/24/24 - Latest circuit attempt wired and tested. It worked!! Generator starts, runs, and stops as expected!!!
John Allison found broken hose clamp on back side of generator that fell off hose from pump to heat exchanger(?). New hose clamp installed. Water vacuumed out of generator drip pan, generator tested. Generator starts, runs, stops as expected. Not sure if all of the leaks are resolved - but definitely resulting in MUCH less water in the drai pan now! This is a significant improvement.
Working on 3D printing a new knob for the helm electrical panel transfer switch. This is a process of trial, test, adjust, and repeat to attempt to get the right dimensions.
12/20/24 - After more than 3 years!!! I was able to start the generator (in the engine room), disconnect shore power, rotate the transfer switch to run the house from the Generator - and power the boat circuits from the boat's generator!!! Somewhere during the re-wiring of the electrical panel in the prior year, I lost part of the knob for the transfer switch. After 10 attempts, I was able to gradually dial in the design of a new knob to precisely fit the shaft of the transfer switch. Now I just need to figure out how to wire the switches from the boat's electrical panel into the generator to remote start - so that I don't have to go into the engine room to start/stop the generator. Generator was run for 20-30 min. No water in drain pan!!!!
12/21/24 - Generator wired to start/stop switch on main helm electrical panel. Generator started and ran from helm position for first time in at least 3 years!!!!
To do's.... I ran a wire from the windlass breaker (not used) to the generator to be used for switching the battery contactor. I would like to have the battery go to a breaker, then a contactor, then to the generator. Then I will also need to do a oil change and fuel filter change. At least the water pump impeller is known to be new and good!
~4/6/25 - After returning from 2 hour outing with generator running, discovered a significant pool of diesel fuel in the drain pain of the generator. Cleaned up, monitored, and on 4/6/25, ran the generator for about an hour in the slip. No further leakage found. Source of prior leak unknown.
4/10/25 - Performed oil and oil filter change. Then performed fuel filter change. See options for filters below.
Parts used:
Fram: PH3593A (Oil) - $10 / Amazon
Donaldson P551744 (Fuel) - $56 (including tax) Amazon
Both filters came off easily. Fuel filter had to be cranked down tightly to get it to not leak. May be difficult to remove... Ran generator in the slip for 2.5 hours - no leaking observed. 112.3 hours (4448.4 main eng hours)
IMPORTANT!!!
Portable generators MUST be run at least every 2 weeks, or the fuel will turn to varnish in the carb, and the carb will need to be rebuild or replaced.
Portable generators typically have a FLOATING GROUND. The ground needs to be tied to Neutral (CORRECTLY!! WATCH POLARITY!!!) for 3 wire electronic devices to work.
Currently priced at $800 at Harbor Freight (7/9/24). The Predator 2000 is about $600. I got my 3500 on sale, seems like it was about $650 on sale?
https://manuals.harborfreight.com/manuals/63000-63999/63584.pdf
These work great when they run. Reviews show tests where the Harbor Freight 3500 is quieter than the Honda and other brands - maybe even quieter than the Honda 2000.
But... To keep them running, they MUST be run every 2 weeks for 10-15 min, or the carburetors WILL gum up, and they'll die.
Sadly, I had the misfortune of letting mine sit too long (maybe 6 months?) - and no, it would no longer start at all.
I ended up buying a service kit on Amazon:
https://www.amazon.com/gp/product/B0C2XZ44XB/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
For $32, that had a NEW carburetor, spark plug, air filter, etc. There are videos that show how to clean the existing carburetor - but for $32 (and less if all I got was the carb), it seemed much easier to just replace the entire assembly and not worry about getting all the jets clean and all the parts back in the right places.
Here are two youtube videos that were very helpful with hints on how to pull the carburetor, sparkplug, and do an oil change (I really should do that soon too):
https://www.youtube.com/watch?v=3r9Bodn7BSw ## How to clean the carb - but shows how to remove it.
https://www.youtube.com/watch?v=b5VgQ_AKCdY ## General maintenance
I also replaced the battery (again, Amazon):
https://www.amazon.com/gp/product/B00K537UJQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
The new battery was $25.
I'm happy to report that the generator is running again!!!
Cover from Amazon that fits the Predator 3500: ($19)
I also have a 2000W Champion Portable Generator. These are now (July 2024) going for $630 on Amazon. I purchased this one for $399+tax in June 2021.
https://www.amazon.com/gp/product/B0812PNK3X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
This cover from Amazon works great to protect the generator:
https://www.amazon.com/gp/product/B0B8Y4WFZ2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Below are the part numbers from the Onan manual, that were cross-referenced online:
Oil Filter:
Prior Oil filter when boat purchased: Fleetwood LF34622
Onan 185-2123
Fram: PH3593A
AC Delco PF1127
Fuel Filter:
Prior Fuel filter when boat purchased: Parker/Racor R245
Onan 149-1914-04
Donaldson P551744
Carquest 86426