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Anybody here ever had this problem with their Onan 6.5
The gen runs Perfect in a cool bilge. My first hot day running around the girls fired up the gen for A/C and after 10 minutes it shut down. Was hard to restart but then cut out again after 10 minutes again. I had wondered why someone had put a small bilge blower in with hose coming from the bottom of the bilge and terminating right on the points housing (see pic of gen)
While researching through the mounds of paperwork that came with the boat I found some e-mail correspondences from the previous owner and a Onan tech describing this exact problem (funny how the widow didn't mention this) The tech said that the condencer was getting too hot in the heated bilge. The gen will run perfect for weeks while sitting at the dock. I've discovered that while out running if I leave the hatch over the gen open about 6 inches to let out some heat it runs great (dangerous). This is one of those weird problems thats on my "Major" list to tackle when nothing else to do.
Has anybody here heard of this happening?????
Ron
When you can't make them see the light, make them feel the heat.
Ronald Reagan
1987 F36 Tri-Cabin
Twin 270 Crusaders
"Special K"
Upper Bay, Chesapeake Bay
I had one do the same thing on a houseboat we lived on while building our house. I ended up putting a 110 volt blower in the engine compartment that ran anytime the generator ran and was ducted outside to keep the engine room cooler. Worked very well. Just be carefull of what type of motor is runnig the blower. I used a totally enclosed motor. Some people might say its dangerous because its not marine/ignition protected but it will keep gas fumes out of bilge also. Added benifit I think.
I'm going up to the marina this PM in order to watch my boat being winterized. I like to be there when they drop it.
While I'm up there, I'll ask the mechanic (he's a good one) if he's ever heard of this situation before and if not, what he might suggest is the problem.
The stator/rotor assembly on a generator is air cooled. They can generate a lot of heat in a poorly ventilated engine room. I measured the temp on a hot july day over 140 degrees in my engine room sitting on the hook with genny running. With the blower we reduced the temp to almost outside ambient. Solved my problem.
Mechanic said "Yes, you're correct, if a condenser gets too hot it could cut out and then, upon cooling it would work again until it heated up once more."
But, he also ventured his opinion that. in his experience he has run into very few similar hot condenser situations.
He thought from what you were describing that probably the automatic cut out switch was being triggered due to a high engine temp as a result of a partially functioning impeller.
He said new impellers these days are manufactured in China and sometimes spin on their center. So even if you have a new one, it may not be golden. He said to check that.
He also said with boats of our vintage (all manufacturers), he sometimes encounters worn impeller housings, whereby sand and other debris have scribed the inside of the housing enough to create a poor seal, even with a new impeller installed. This means enough cavitation to drop the water flow to less than 100%. Gradually, the gennie will overheat in this case.
He said to remove the impeller and inspect it and then inspect the inside of the housing. Any problems with the inside of the housing will bevisible to the naked eye.
I agree with the raw pump. And yes a condenser will over heat. Had the condenser trouble before. If you do a check on the site you can fined all the parts I and a couple of the guys used to update our onans to get rid that 60'points system.. if you can't find them let me know. I'll be glad to give you all the info I've gotten over the pass couple of yrs
Carver 3607 ACMY 454's Merc's
10' Dinghy 6hp Merc.
La Dolce Vita
Let's hit the water !
ron, also, do not over look the thermostats. these little buggers are only a half inch round and roughly and inch in height. they can corrode and clog very easily, especially with marine crud. if you recall, my genset on this tri cabin had only one thermostat. you might want to replace them, get a new impeller (mine had 3 out of 6 blades left) and flush the genset with the marykate on&off. while i know it's the end of the season, at least it will be stored 'clean'. i know that when i dewinterize, john and i are going to adjust the carburetor and governor linkage too.... she's running way too slow and when i apply the reverse cycle, my volt meter reads just a tad over 100volts.... that's way too low. it should read roughly 110 or a little below. once john and i did this to my other genset on the f-32, she handled any load i could put on her. these gensets are bullet proof, but they need to be tended to from time to time as i'm sure anyone will agree. sure wish i had the kohler from our original tri cabin. that baby could handle anything and from what i understand, nearly 40 years later, still could.
tony, what did you do to upgrade your onan? i'm curious.
flying the boston shuttle all day today (1130-2145, two round trips) so i need to get ready to go to work. naturally, i'd rather be putzing around on the tri, but hey, it's a living.
aaron
1982 F-36 TRI CABIN ENTERPRISE
PARKSIDE MARINA IN MIDDLE RIVER, MD aaronbocknek@gmail.com
It was tired when I got the boat. I did my best to nurse it along until she stopped charging in 2003.
Tried to replace the brushes, but all the bolts were so rusted that they just broke off. Once I really started looking at it I was surprised at just how rusted everything on that genny was.
Replaced it with a 5kW diesel genset that is certified to run in a gas environment on it's own custom built 17 gallon fuel tank.
Weighs less than the 6.5 and burns less than 1/3 gallon of fuel while running the A/C.
with the addition of a gen sep, it's quieter than the 6.5
Runs my 16,000 BTU HVAC and everything else nicely. Starts every time, no choke no issues, no problems.
Didn't mean to hijack the thread, but when the costs to repair the old uni whos condition and life expectancy is questionable, it's time to seriously consider alternatives.
Your's probably needs just some maintenance, but I wanted to share my own experience and results for future reference.
RWS
1983 10 Meter SOLD after 21 years of adventures
Yanmar diesels
Solid Glass Hull
Woodless Stringers
Full Hull Liner
Survived Andrew Cat 5,Eye of Charley Cat 4, & Irma Cat 2
Trojan International Website: http://trojanboat.com/
It was tired when I got the boat. I did my best to nurse it along until she stopped charging in 2003.
Tried to replace the brushes, but all the bolts were so rusted that they just broke off. Once I really started looking at it I was surprised at just how rusted everything on that genny was.
Replaced it with a 5kW diesel genset that is certified to run in a gas environment on it's own custom built 17 gallon fuel tank.
Weighs less than the 6.5 and burns less than 1/3 gallon of fuel while running the A/C.
with the addition of a gen sep, it's quieter than the 6.5
Runs my 16,000 BTU HVAC and everything else nicely. Starts every time, no choke no issues, no problems.
Didn't mean to hijack the thread, but when the costs to repair the old uni whos condition and life expectancy is questionable, it's time to seriously consider alternatives.
Your's probably needs just some maintenance, but I wanted to share my own experience and results for future reference.
RWS
believe me, nothing would please me more than to yank out that 'paperweight' i have in the bilge. i'm not a huge fan of the mcck, especially after seeing how those exhaust mixers rot away. i'd love to replace it with a new kohler or westerbeke, but for now, i do not have the bucks to do it. my mechanic is watching out for a good used unit though so eventually, what i have in there will go and be replaced with a newer model. i just need to gather the funds to have it done.
aaron in baltimore
1982 F-36 TRI CABIN ENTERPRISE
PARKSIDE MARINA IN MIDDLE RIVER, MD aaronbocknek@gmail.com
You guys are sooo Awesome!!! Thanks for the help! In the 5 years I've been working on yachts I've never had to mess with Gens because I had a guy who thats all he did. Sadly the "Old timer" moved to Fla. a month before we got this Tri.
While going through the paperwork for this boat I found a reciept from a rockhall marina from spring '09 where they tore apart the entire Gen then replaced almost everything on it except the block. Even a new water pump housing, carb, fuel pumps, hoses, wires, muffler etc. The last dude obviously had the same issues.
Please keep the ideas coming since I plan to tear it apart myself in January
Thaks again Ron
When you can't make them see the light, make them feel the heat.
Ronald Reagan
1987 F36 Tri-Cabin
Twin 270 Crusaders
"Special K"
Upper Bay, Chesapeake Bay
Considering all the work that has been done, perhaps tearing it all apart to re-do that is not advisable.
I do know that my new diesel genny has a temp sensor that will shut it down in the event of overheating.
Perhaps yours has a similar system that needs attention to the sensor or the wiring harness?
RWS
1983 10 Meter SOLD after 21 years of adventures
Yanmar diesels
Solid Glass Hull
Woodless Stringers
Full Hull Liner
Survived Andrew Cat 5,Eye of Charley Cat 4, & Irma Cat 2
Trojan International Website: http://trojanboat.com/
Going down to work on my genset this morning , replacing a temp cut off switch . Gensets have so many cut of switches it can be a problem finding what on is causing issues some times . I just replace my elbow and could not remove my switch with out breaking it so I am replacing it .
RWS what brand Genset do you have ?
Last edited by prowlersfish on Sun Nov 07, 2010 4:43 pm, edited 1 time in total.
Boating is good for the soul
77/78 TROJAN F36 Conv.
6BTA Cummins diesels
Life is to short for a ugly boat
RWS wrote:Considering all the work that has been done, perhaps tearing it all apart to re-do that is not advisable.
I do know that my new diesel genny has a temp sensor that will shut it down in the event of overheating.
Perhaps yours has a similar system that needs attention to the sensor or the wiring harness?
RWS
That's a good point RWS. Forgot about that.
A few years ago the GM genny on my Searay stopped working. Would start perfect then as soon as I let go of the start switch cut off. Discovered it was the "low oil" sensor clogged up with gunk. Replaced it for $31 and it ran great till I got rid of her. Perhaps I should do an Ohm test on it.
Ron
When you can't make them see the light, make them feel the heat.
Ronald Reagan
1987 F36 Tri-Cabin
Twin 270 Crusaders
"Special K"
Upper Bay, Chesapeake Bay
Basically it's a Kubota 2 cyl diesel running at 2400 RPM spinning a Markon generator spinning at 3600 RPM
PArts will be easy and affordable.
Other than oil, filters & zincs, we've only had to replace the oil pressure switch.
She has almost 800 hours on her since 2003.
RWS
1983 10 Meter SOLD after 21 years of adventures
Yanmar diesels
Solid Glass Hull
Woodless Stringers
Full Hull Liner
Survived Andrew Cat 5,Eye of Charley Cat 4, & Irma Cat 2
Trojan International Website: http://trojanboat.com/
