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Old 28 September 2007, 16:14   #11
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Engine Flushing

My understanding is that on modern engines you may have two flushing options:-
1. Muffs on the water intake which requires the engine to be running on idle in order to pump the water around all the engine. This is the best method of flushing the waterways but requires a good flow of water and close fitting muffs to ensure adequate cooling.
2. A hose fitted directly to the flushing point, usually located on the side of the main motor. This must be used without the engine running as the water pump/impeller is not getting a flow of water which acts as a lubricant and as a consequence will quickly be damaged. I would only use this facility when option 1 is impossible eg when the boat is afloat in a marina berth and the engine is tilted out of the water.
No doubt others have different views!!!
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Old 28 September 2007, 17:29   #12
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Originally Posted by jyasaki View Post
Using a hose adaptor on/near the head of the engine, generally you do not run the engine. Input is after the thermostat, so the heads entire water jacket is flushed.


jky
Thanks for that good information.

If you are right that the direct hose connector is after the thermostat on my Yamaha 60, then that makes good sense, and no, absolutely no need to start the engine.

But is that 100% sure? Is there a complete separate cooling circuit for the direct connection? If so, then this must be the best and most thorough way to flush.

(When I flush like this, engine off, water comes out of the bottom of the engine leg, through the prop and the water intake - how does it get past the closed thermostat?!)
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Old 29 September 2007, 00:56   #13
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Originally Posted by bernithebiker View Post
Thanks for that good information.

If you are right that the direct hose connector is after the thermostat on my Yamaha 60, then that makes good sense, and no, absolutely no need to start the engine.

But is that 100% sure? Is there a complete separate cooling circuit for the direct connection? If so, then this must be the best and most thorough way to flush.

(When I flush like this, engine off, water comes out of the bottom of the engine leg, through the prop and the water intake - how does it get past the closed thermostat?!)
Well, if you want it from the horses mouth, go to the Yamaha website and read the owners manual. It's written by the guys who designed the engine, so they should have a pretty good grasp of correct procedures.

http://www.yamaha-motor.com/outboard...d_manuals.aspx , and enter the year and model.


And realistically, if the water source is after the thermostat, the only parts not flushed are the impeller housing, and the water tube leading to the thermostat. Not really a lot to wear there (and all pretty much vertical, so it's not going to pool and evaporate, which is where most of the salt buildup comes from.)

No separate cooling circuit with the hose adaptor at the powerhead; it's just an opening into the circuit that is normally pressurized by the impeller (try undoing it for a brief moment while running; you'll probably get a bit wet, though.)

jky
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Old 29 September 2007, 13:15   #14
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Do the muffs in any way muffle the sound of the engine if you are running it out of the water? I imagine it must make one hell of a racket.

Or is that a stupid question?
Quite a sporty exhaust note on my Johnson, especially if you blip the throttle

Guaranteed to get the attention of neighbours and indeed anybody else within 1/2 mile
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Old 30 September 2007, 09:09   #15
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I have a 2006 Yam 80 4 stroke & after much research & many different opinions, flush with direct hose connector whilst cleaning down boat (say 3 mins or so), then, hook up the muffs & give it another 3 mins or so idling.

Maybe a bit OTT but the salt is v corrosive here in Spain & I plan to keep the boat & ob in tip top condition.

When flushing via direct hose connector there is water egress from lower leg so I think there is a bypass mechanism, or backwash, which cleans out the impellor & thermostat. Otherwise, why would Yam fit such a connector if it only did half a job.

Anyway, lots of diff opinions & views as usual.
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Old 30 September 2007, 17:17   #16
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When flushing via direct hose connector there is water egress from lower leg
Which parts of the lower leg?
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Old 01 October 2007, 07:05   #17
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On my Suz there is a small amount of water down the prop exhaust - I assume it is because when you're running flat out the amount of water needed to cool the engine will not all get through the tell-tale nozzle (the name gives it away, otherwise it would be called the cooling outlet?) and the easiest place to dispose of it is down the leg and out through that nice big hole in the middle of the prop. Also when afloat the static pressure at the prop results in the exhaust leaving above water thru' the silencer, but the coolant that isn't exiting via the tell - tale has to go somewhere - take it out the water and that back pressure isn't there, hence why the tell tale isnlt so forceful?

My prop has a flared trailing end to the hub, I assume it's to act in a similar manner to a "wedge" self bailer, create a slight vacuum in the exhaust and either pull more coolant through or get the exhaust out the cylinder quicker (probably a bit of both).

For what it's worth I have discovered I can put my hand over the prop exhaust (fingers clear of blades!) and it makes no difference to idle speed (same as it being underwater) - also makes the muffs a far more sociable method of flushing! (this winter's plan is a wooden bung with a small vent hole or two to keep it quiet next season)
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Old 01 October 2007, 11:45   #18
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Which parts of the lower leg?
F115 has water coming out all over the damn place. Telltale, through-hub, and about 10 or 12 little jets or dribbles from all kinds of openings on the leg (some that I didn't even know existed.)

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Old 02 October 2007, 11:09   #19
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yes thatīs the same on the f80, lots of water egress points when hooked up to direct hose connection as previously posted here. Tell tale, through prop, small hole at leading edge of gearbox, plus many others.

Starting to think that it pretty much flushes everything or it wouldnīt have been fitted - Yam are no fools. Anyway, till I hear otherwise I am going to keep flushing via the muffs too.
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Old 02 October 2007, 13:16   #20
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Originally Posted by 9D280 View Post
On my Suz there is a small amount of water down the prop exhaust - I assume it is because when you're running flat out the amount of water needed to cool the engine will not all get through the tell-tale nozzle (the name gives it away, otherwise it would be called the cooling outlet?) and the easiest place to dispose of it is down the leg and out through that nice big hole in the middle of the prop. Also when afloat the static pressure at the prop results in the exhaust leaving above water thru' the silencer, but the coolant that isn't exiting via the tell - tale has to go somewhere - take it out the water and that back pressure isn't there, hence why the tell tale isnlt so forceful?

My prop has a flared trailing end to the hub, I assume it's to act in a similar manner to a "wedge" self bailer, create a slight vacuum in the exhaust and either pull more coolant through or get the exhaust out the cylinder quicker (probably a bit of both).

For what it's worth I have discovered I can put my hand over the prop exhaust (fingers clear of blades!) and it makes no difference to idle speed (same as it being underwater) - also makes the muffs a far more sociable method of flushing! (this winter's plan is a wooden bung with a small vent hole or two to keep it quiet next season)
It actually sounds like you need a new impeller fairly soon. The telltale should get stronger the faster you're going and there should be quite a lot of water coming out of the prop hub.
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