6.5 onan

fpawn1 · Post by **fpawn1** » Sun Jul 24, 2011 10:33 am

Started a project on my 19981 gen set. I have had the carb rebuilt, 2 hew thermostats, all new hoses, gas pump, and impeller. Had to take intake head off since it was clogged and cleaned it out. Starts up fine, giving out plenty of juice, but very little water is being pumped out. Mechanic says its fine, but use to--has not worked in 2 yrs--to pump more water I thought. Any thoughts on such

alexander38 · Post by **alexander38** » Sun Jul 24, 2011 3:23 pm

If I'd had it tore down that far a raw water pump rebuild would've been done.

Big D · Post by **Big D** » Sun Jul 24, 2011 9:20 pm

Ditto the water pump. Closed cooling? If so, did you clean out the heat exchanger?

fpawn1 · Post by **fpawn1** » Sun Jul 24, 2011 9:25 pm

its raw water cooled---disconnect hose and pump is working fine---only took one head off

prowlersfish · Post by **prowlersfish** » Sun Jul 24, 2011 9:33 pm

exhaust riser can plug up

alexander38 · Post by **alexander38** » Sun Jul 24, 2011 10:13 pm

Have u checked the temps with an IR temp reader? Easier to fined out if its cooling well enough. And its a great tool to have to check all your risers and heat exchangers

sluggo · Post by **sluggo** » Mon Jul 25, 2011 11:24 am

fpawn1 wrote:Started a project on my 19981 gen set. I have had the carb rebuilt, 2 hew thermostats, all new hoses, gas pump, and impeller. Had to take intake head off since it was clogged and cleaned it out. Starts up fine, giving out plenty of juice, but very little water is being pumped out. Mechanic says its fine, but use to--has not worked in 2 yrs--to pump more water I thought. Any thoughts on such

I think on mine, there is a sensor that makes it cut off if it gets too hot, I know mine doesn't throw a ton of water, it never really has.

alexander38 · Post by **alexander38** » Mon Jul 25, 2011 1:50 pm

Yeap sensor will cut out on over heat . Mine did it the other day underway good water flow but the eng room temp was just to high

aaronbocknek · Post by **aaronbocknek** » Thu Jul 28, 2011 7:18 am

i've worked on two different models of the onan mcck with my mechanic. the first one was a 1976 (spec G) and my current one is 1982 (spec H). in spite of the small size of the water pump, you should be getting good water flow, (the water flow should be constant, not water then 'dry exhaust'. you can also tell if things are not quite right by the sound level. if the sound level is loud, then there is something clogging the water flow) even if your aqua lift muffler is big, as is the case on my tri cabin. the best thing john (my mechanic) taught me is to do an 'acid flush' twice a year. at the beginning of the season, and at the end of the season. one simply pours some marykate on/off into the water jacket via the raw water intake hose using a funnel. switch the unit on for just a second via the controller to get the acid into the system. keep doing this until the entire bottle is empty. let it sit for a good 10-15 minutes. then, pour water into the intake hose again in case there are any air bubbles, cover the hose with your finger and reconnect it. USE GLOVES WHILE YOU DO ALL THE ACID FLUSH THOUGH. run the unit and watch the 'diotomacious ooze' run out the exhaust. this acid flush will make the unit run cooler and your water flow will be 'normal'. any buildup in the exhaust mixer elbow will be eaten away too. i cannot over emphasize enough that these gensets NEED to be run, once a week (per the manual) for at least 30 minutes. this not only makes the units start better, but it keeps the cooling system clear. the more the set is run, the better it will be. they are not designed to be paperweights in the bilge.

tri cabin aaron

prowlersfish · Post by **prowlersfish** » Thu Jul 28, 2011 8:08 am

Aaron is correct they need to be run . But they like any marine engine they need to be run under load . not just run .

Big D · Post by **Big D** » Thu Jul 28, 2011 9:47 pm

+1 +1. Use it or lose it.

alexander38 · Post by **alexander38** » Thu Jul 28, 2011 10:26 pm

+1+1+1 that goes for the main engines too

aaronbocknek · Post by **aaronbocknek** » Fri Jul 29, 2011 6:49 am

prowlersfish wrote:Aaron is correct they need to be run . But they like any marine engine they need to be run under load . not just run .

thanks paul, 'run under a load' (50-60% at least) was implied, but i should have been a little more clear. the bottom line is the water flow should be fairly constant, allowing for the buildup in the lift muffler if your vessel indded has one. my f-32 did not have a lift muffler, just a small straight shot one and the water flow, once all the crud was cleared out of the water jacket was constant and quiet.

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