Flushing the engine when in the wet stuff

[oGaryo]

sorry for the naive and somewhat lazy question... will be moving the boat to a marina next year and have decided on the marina to go to so am looking forward to the convenience factor of having the boat in the water ready to go but need to understand the change in maintence approach I'll need to adopt. the boat's currently on a trailer so flushing the engine is an obvious difference as is anode maintence, seacock checks and bum scrub..

what I don't know is how do I flush the engine and sterndrive after each trip if the boat's in the water? I am meticulous when it comes to flushing the engine at present and would like to continue to look after it with the same level of dilligence when in the marina... it's a raw water cooled mercruiser 5.0l MPI with alpha 1 gen 2 leg.

will start reading up in the next few days but would welcome advice on this aspect and any aspect of moving a boat to a marina for the first time.

many thanks Gary

 

[MapisM]

what I don't know is how do I flush the engine and sterndrive after each trip if the boat's in the water?
...
it's a raw water cooled mercruiser 5.0l MPI with alpha 1 gen 2 leg.

Mmmm... That's tricky. The raw water pump is inside your outdrive, therefore I would think that the only way to flush the engine with fresh water is with a hose and a flusher attached to the leg - the same as you probably used to do with your boat on the trailer.
How feasible that is (or not) with the boat in the water, it depends on how deep is her waterline and how accessible the outdrive is from the swim platform.
Not the nicest way to end a day of boating anyway, particularly in cold waters...

It would be completely different with a Bravo leg, where a simple T adaptor on the hose from the leg to the pump on the engine would do the trick, but I suppose you wouldn't want to change the outdrive for that reason alone...

 

[Mike k]

I will be interested to follow this thread as i do not flush my engine each time i use it- i am in seawater permanently and was told that it is unneccessary- i am fresh water cooled with raw water heat exchanger - single prop shaft drive 250hp 4.2 d- looking forward to hearing comments.

 

[Divemaster1]

Mmmm... That's tricky. The raw water pump is inside your outdrive, therefore I would think that the only way to flush the engine with fresh water is with a hose and a flusher attached to the leg - ......

Without knowing the engine, surely the raw water cooling is not completely enclosed throughout.... What would stop one putting a T piece in with a ball valve, then a one way valve above it with a connection point for the flushing water??

Then let the pressure of the waterhose push water through ...but there will be salt water in the leg as it constantly would be immersed ... then temperature differences would cause water circulation .... probably..... so is there any point in flushing the engine, if in the water and no air getting to the cooling system ??

 

[MapisM]

i do not flush my engine each time i use it- i am in seawater permanently and was told that it is unneccessary

Well, it all depends on what unnecessary really means...
Engines, ourdrives, heat exchangers, risers, etc. are indeed built to withstand salt water.
But in my experience, it takes 4 or 5 years of fresh water usage to get anywhere near the effects of one season in salt water.

 

[MapisM]

Without knowing the engine, surely the raw water cooling is not completely enclosed throughout.... What would stop one putting a T piece in with a ball valve, then a one way valve above it with a connection point for the flushing water??

Then let the pressure of the waterhose push water through ...

Good point, I'm not sure about how the water flows from the outdrive to the block in Merc Alpha sterndrives.
It might be fully enclosed, though. But maybe not.
Worth some further investigations, anyway.

 

[rafiki_]

Gary,

We used to have a similar set up, although OMC engine and drive on the river Bure in Norfolk. This was tidal hence sea water, and never flushed with fresh water until she came out in the winter. Didn't appear to cause a problem in the 3 seasons we had her there.

 

[Divemaster1]

Good point, I'm not sure about how the water flows from the outdrive to the block in Merc Alpha sterndrives.
It might be fully enclosed, though. But maybe not.
Worth some further investigations, anyway.

Looks like front left side have a filter unit .... T piece could go there...

 

[KieranW]

My understanding of it is that as long as there is no air going through the drive you have no more chance of rust than you would have if you flushed out the drive and dry stored it.

Rust needs air to form and while there is air (oxygen) in sea water it would be a really slow process for rust to form, no faster than it would be if it was caused by the salt left in your drive after flushing and there will always be some)

That's what I was told any way.

 

[carlton]

Gary - you could take the easy option and don't bother flushing. You'll need to budget for replacing mans/risers every five years if used in saltwater.

 

[tinkicker0]

Cooling water on the gen 2 enters the boat via a 3/4" rubber hose located near the top of the transom shield above the driveshaft.

 

[oGaryo]

That's what i was thinking TK... some sort of setup to inject water at that point towards the engine and allow saltwater from the sterndrive to be redirected overboard... however, as said, probably best to just budget for replacement risers etc and spend the time each season checking them for premature corrosion instead

 

[penfold]

Alternatively get your motor converted to freshwater cooling with an intercooler and associated plumbing, then you don't need to worry about it.

 

[oGaryo]

Alternatively get your motor converted to freshwater cooling with an intercooler and associated plumbing, then you don't need to worry about it.

like the sound of that... any idea how much that'd cost (ish)?

 

[carlton]

A lot more than a new set of mans/risers every five years!

 

[oGaryo]

A lot more than a new set of mans/risers every five years!

yep, just looked around, not cheap.... it's looking like a case of plop the boat in the wet stuff and don't create a daily hassle factor.. which sort of defeats the object of moving the boat to a marina in the first instance... will check the manifolds and risers before we move her and replace if necessary before we move her.

thanks for the advice all, appreciated

 

[carlton]

Gary - I assume you don't know for sure when they were last changed?

I've discovered that mans/risers don't suddenly fail. The first sign that they're on the way out is your engine/s start running a little warmer than normal. Just keep an eye on the temps and you should be fine.

 

[oGaryo]

Gary - I assume you don't know for sure when they were last changed?

I've discovered that mans/risers don't suddenly fail. The first sign that they're on the way out is your engine/s start running a little warmer than normal. Just keep an eye on the temps and you should be fine.

thanks, good advice. temp is fine at present and I ended up changing the riser and manifold on the old boat (had a 3.0l straight 4 installed)... tried the route of de gunking it with acid which sort of worked but loads of hassle and no telling if the water jacket walls were thin so safest option is to watch the temperature, look for rust streaking at the joins and inspect annually I guess. The previous owner told me his engineer checked them annually and I'll be checking them for the first time this year...

They've not been replaced in 8 years I reckon according to the receipts I have so reckon they're due a change considering the boat was kept in the water prior o my ownership.

Will defintely check them out especially as inspection looks easier on the 5.0l mpi block with two rubber gaitors on the risers... thanks again for the advice

 

[MapisM]

Alternatively get your motor converted to freshwater cooling with an intercooler and associated plumbing, then you don't need to worry about it.

You're saying that as if with freshswater cooling the exhaust wouldn't still be cooled by salt water...

 

[andy59]

Gary , as far as i can tell , flush muffs would work while the boat is afloat so i think the only sensible option would be for you to plop yourself in the oggin after using the boat and put on the muffs to flush her out , you know it makes sense !!!