Onan 6.5kw Marine Genset Cooling

[bmalmquist]

Hello, new to the forums and looking for some advice.

We recently purchased a 1984 Carver 3207 Aft Cabin with an Onan 6.5kw Marine Genset. The generator ran great for a couple of trips but just yesterday I went to start it and it did not appear to be circulating any water (this is a freshwater cooled system). I assume there must be a safety shutoff as the generator powered itself down after about 60 seconds.

I am thinking that I will need to replace the impeller but have read that it may have just lost siphon? Is that possible, and if so any hints on how to remedy?
Is it a big job to replace the raw water impeller?
Does anyone have a manual for that year Onan generator?

I have owned many inboard/v drive boats as well as a few older RV's and have done all the work on them myself.

I searched the forums but could not find anything specific to my year/model.

Thank you in advance for any expertise you can provide!

[bud37]

Welcome to the forum......from your explanation I am guessing the water not circulating is the raw cooling water that goes out the exhaust......since the boat is new to you , you have no way of telling when that has been done last, just change the impeller and go from there, probably all it is.....good luck with it.....

[bmalmquist]

Thank you for the reply bud37. You wouldn't happen to have or know where I could find the manual for that year generator? After the exhaust there is a collection tank before it drains out the side of the boat, anything special I need to know about that or it's purpose?

Thanks again!

[bud37]

Since you have recently bought , on your surveyors report should be the year , model and serial number of your genny, if not get those numbers off the plate on it and google same .....perhaps Onan itself has old manuals....there are most likely manuals online for these also.
The tank , if it is black fibreglass is probably the muffler for the generator.....if you have a pic of this, it can be verified as to the type.

[bud37]

Just to check, close the thru hull for the water intake for the generator....remove the hose , get your shop vac on blow, stick over the thru hull valve then open the valve to blow any debris out to remove the possibility of a bag or something being stuck in there.....if there was you will still have to change the impeller, they can't handle running dry.

[Viper]

Don't know the spec you have but this should be pretty close:

https://isurplus.com.au/manuals/Onan%20MCCK%20Marine%20Genset%20Manual.pdf

Replace your impeller. You need to start with a fresh one anyway so that you have a record of when it was last done.

[bmalmquist]

Thank you for the manual link Viper.

I am used to changing my raw water impellers every year in my Malibu Wakesetter towboat, I have been told that it could be a little aggressive to be doing all my impellers on the Carver every year.

It only takes me about 20 minutes to change the towboat impellers, how big of a job is the impeller on the Genset?

[Viper]

It depends on the spec. The earlier vintages were next to impossible unless you removed the carb to make it easier to get at. You'll know right away at a glance whether it's going to be a few minutes or a few hours.

[bmalmquist]

It is a Spec H. It would appear that there will be just enough room by about 3/8 of an inch, to remove the cover and replace. I will let you know.

Any special grease I should put on it for the initial start?

[Viper]

Coat the impeller and inside of the pump housing with a little bit of dish soap. Check the wear plate and cover for excessive wear. If they're heavily grooved, it will affect the performance of the pump and replacement is recommended.