Onan generator

PitterPatter

Does anyone have a Onan Gen?  If so what is normal water flow for a 3MAJB. Mine seems to be weak and lately I think I am smelling a hot rubber smell. I think it is the impeller getting too hot. 

LaRea

Most of us have some variant of the Kohler 5k.  Water flow should be something like a gallon every 15-30 seconds (wild guess).  How hot is the water coming out?  It should be cool enough that you can easily hold your hand in the exhaust stream.  If not, you aren't pumping enough water. Check intake for fouling, and replace impeller.

PitterPatter

Thanks LaRea. The gen only had 18 hours (23 yrs old)and wasn't running when I purchased it last year. This year once I got it running I had a clog. I tracked it down it was a elbow going into the engine. I had a mechanic out since it still didnt seem right. It was rusted and corroded in the thermostat too. I replaced the impeller first thing. I think I will do a flush this weekend with barnacle buster. Thoughts?

LaRea

18 hours in 23 years ... wow, I'm not surprised it's giving you problems.  That's a poster child for why generators need regular exercise.   

You probably already did this: remove the bowl from the raw water strainer, then open the seacock to make sure water is flowing freely into the strainer. 

Once you get it running, check the water temp coming out of the side of the boat as I mentioned above.  If it's too hot, keep looking for blockages.  For the first month or two, run it a lot.  I'd run it under load for 20+ minutes at least once a week.  Then back off to a maintenance schedule of 20+ minutes 1-2 times a month.   

Good luck!  

PitterPatter

I will check thise things. Odly it does not have a strainer. I spoke with my mechanic about adding one so that is in the plan. I have probably more than trippled the the hours on it in the last couple of months. I plan to use it as it was intended to be used. Been having a little popping while running. Mechanic said he couldn't figure that out but was running ok. Just annoying. It has been quite the proccess finding someone who knows how to work on a Onan. Thanks again LaRea

PickleRick

I work on a few old onan motors, mostly in john deere lawn tractors.  I believe your model is a flat head design.  With that many years on it id want to check valve lash.  As the flat head motor wears the valve lash decreases until you have (usually) an exhaust valve not seating.  It will run until this point.

Next are the points and condenser, if it's that old. Use oem or oe replacements, ive found the China ones may last a season if lucky.

The ones i deal with also have an automotive style coil on them, the ones post points have a pick up unit that can cause a miss when failing.

Last but not least, i tell customers if youre going to guess at a repair without proper diagnosis on these motors go with carb repair first since 80% of the time that's the culprit with small engines.

I dont have any experience with ohv onans. 

I have converted an onan generator(rv) engine to run in a large simplicity tractor and the only difference between the two was the tractor engine had a stator behind the flyweel which the genset engine did not. 

PitterPatter

PR, Thank you. Your info is very helpful. I replace the condensor and not sure if the points have ever been changed. I have had three different people look at it. I have mentioned the carb cleaning to all of them. I guess I will have to tackle it myself. I will check the valve flash this weekend. Thanks again!

PickleRick

.009 and .007 come to mind on valve lash. .009 being the exh.

The points(contact) are what usually goes/gives issues.  Filing them creates an uneven surface. If needing to clean i hit them with brake claner then a new clean business card.  When possible i upgrade to electronic ignition system as it has less issues/maintaince but i have never converted an old onan, only Briggs and stihl equipment. Oh and an old 289 mustang

PitterPatter

How do you chec for valve flashing and what do you look for?

PickleRick

Valve lash is checked at tdc on each cylinder.  The space between the lifter and bottom of valve stem.  Continental engines in Greenville sc is who i would call for parts and to verify valve lash specs. Make sure you have the model and spec for the engine when you call. They are who i go to for any onan parts. They ship all over the usa, used to have an orlando branch.

PitterPatter

Thank you PR!

PickleRick

No problem at all!