Engine Flushing

NRath

Tagging onto the thread about fresh water flushing w/o trying to hi-jack it brings me to a question about when the engine needs to be flushed.   Running in brackish (or salt) water, it's easy for my rookie self to assume it should be flushed after every trip.  What's the consensus on fresh water?  

This has been my first summer with a boat and I haven't been flushing it as it's been freshwater only.  I'm thinking as long as the outdrive isn't being grounded/beached, it should be good to go.  My trip back to the ramp always includes a few minute run on plane (10-25 ft water), so it should be pushing some clean water through if I did manage to stir up some dirty water back in a cove or something.  Heck, my tap water comes from this lake.  Granted they clean it up a little first.

What do you guys think?

MarkB

I am on Lake Ontario. I NEVER have flushed my raw water cooling system (through the block). I replaced my thermostat this season, and the old one looked brand new.

Michael T

@NRath - I have never flushed a fresh water engine. I have helped friends flush fresh water engines that ingested sand from a sand bar or algae from fishing in weeds then having the engine temp go up. But - I agree with you - no need to flush a engine used in fresh water unless there are exceptional circumstances.

Dream_Inn

Yeah, should not be a problem.  I don't see it an issue in brackish water either.

Michael T

@DI, I would flush in brackish water.

NRath

Having seen what salt will do even in limited exposure, I agree with MT and would flush and spray off the outdrive if my stuff gets near saltwater (brackish).  My '06 V-P 4.3 GXi has 80 hrs, 2 yrs near brackish/saltwater and the remainder in fresh water.  There is corrosion speckled around on my outdrive.

NRath

Good to hear I wasn't off base with my freshwater flushing.

Once there is some small amounts of corrosion, is it like rust in that it will continue grow regardless of environment?  Or, once it's removed from the salty environment, will it stop spreading?

Handymans342

I even wash my cars with salt away to get the winter salt off.

NRath

NRath said:

"will it continue grow regardless of environment"

Scratch that.  A quick google search confirmed it will.  There was a wee bit of wishful thinking that it might not.  I can see myself pulling the outdrive to sand, protect, and repaint the whole thing.  Likely next winter.  Will have to do a little preventive patching this year.

Dream_Inn

Well, I do wash off my outdrive and the boat a quick spray after each outing (benefit to being on a lift).  I guess I just hadn't seen much difference in running the engine on fresh water after each use, of course I'm happy I have fresh water cooled, but my risers/manifolds still have brackish go thru them.  Maybe I was lucky, but my 310 after 10 years of brackish, risers/manifolds still looked like new.

Handymans342

Someone told me that salt water is not so tough on Diesels. Might have something to do with the heat ex-changer design vs Gasers. I will ask my Yanmar mechanic

MarkB

I do not believe that.  A metal has to be used to transfer heat (cool).  Any metal that's in contact with sea water, at elevated temperatures that isn't going to cost $10,000 is going to have corrosion.

NRath

Dream_Inn said:

Maybe I was lucky, but my 310 after 10 years of brackish, risers/manifolds still looked like new.

How did the outdrive(s) look?  V-P or Mercury?

Handymans342

Probably good since he keeps his boat on a lift. I painted my drives with outdrive antiablative paint or what ever it is but I too will be on a lift.

Dream_Inn

Handy is correct.  My outdrive looked like it would in the showroom, waxed and shiny new since it was lift kept.  But the lift portion had nothing to do with the risers/manifolds staying nice.  It would made it much easier to flush if I had done that.  Oh, they were Merc B-3s

Michael T

From my standpoint (and remember I am ocd when it comes to prevenataive maintenance) I just ask myself what my time was worth. It takes me 5 minutes start to finish to flush my HVAC and Generator using my system - maybe 4 minutes or even less with a production "automatic" flush. So, is my 5 minutes worth it. If I boated in brackish water would I flush my engines. Are you kidding me? Darn right. Why do you think you change from magnesium to aluminum anodes going fresh to brackish water and aluminum to zinc when going from brackish to salt. There's a good reason guys. BTW the spots of corrosion on a drive, yes, the first signs of trouble, neutralize, sand, prime, paint and wax. IMO...... BTW, my fresh water flush (and the "automatic" production units too) can ALSO be used to prime my HVAC and Generator (both of which are a real pita to do on my EC 360) AND also be used to run anti-freeze through them to winterize.