Generator can't handle rated load

[Sojourner]

Hey all, it's been a while.... hoping y'all are doing great! And hoping someone has some knowledge of my generator problem.

It's an old (30 y/0) Onan 6500 marine genset in my amel super maramu. Symptoms are: gennie holds loads fine up to about 2000 watts of demand, but much above that (but well below 6500) it will cut out the production of power for a minute, the engine speeds up as the load comes off, then in a minute or even less, it cycles back to engine under load and the watts coming back online. So it works to a point all day long (at half load or less) but then will cut totally out and back if I put too much load on. The engine side has been serviced/rebuilt last year.

What can I look for to see why it can't handle even half it's rated load? Mech/fuel side possible? The filters were changed last year too. Voltage regulator? Motherboard thingy? The local mechanics want to pull the whole thing to fix whatevers wrong but that's a huge job here and I'd rather wait or replace it if that's the case.

Any thoughts would be MUCH appreciated!
All the best
Davi
SY Wake

[GordMay]

GENERATOR TROUBLESHOOTING GUIDE
➥ https://www.flightsystems.com/pdf/on...ting-guide.pdf

More Troubleshooting and Cross-Reference Guides
➥ https://www.flightsystems.com/troubleshoot

[rslifkin]

Can you find and post the model number from the dataplate on the unit? Some of those old Onans can be a little bit fussy and hard to find parts for, but the basic units are pretty simple to work with and all of the manuals and lots of knowledge are floating around the internet. So once we know what you've got, we can likely find you better info to hunt down the problem.

[Sojourner]

It's an Onan 6.5 Marine Genset... I don't have the model number at hand right now. Someone suggested it might be a fuel starvation issue, ie the revs go too low for the force needed to produce more than 2000 or so watts, and then it clicks the power generation off, spins back up, then tries again over and over. I'm going thru the fuel system now, starting with the filter. Here's hoping it's that simple

[rslifkin]

Is it gas or diesel?

[Spot]

I have gotten good advice from the forum below on a Kohler generator issue and one guy even sent me a couple parts without me asking. It's a little slower paced than CF so don't be surprised if you don't get a reply to posted question for a couple days.

https://www.smokstak.com/forum/forum...-generators.1/

[rslifkin]

Originally Posted by Spot

I have gotten good advice from the forum below on a Kohler generator issue and one guy even sent me a couple parts without me asking. It's a little slower paced than CF so don't be surprised if you don't get a reply to posted question for a couple days.

https://www.smokstak.com/forum/forum...-generators.1/

I'll second that place as "the" resource for old Onan stuff. Some of those guys have been messing with them for longer than the rest of us have known the word "generator".