Engine flushing - do you run your engine?

[9D280]

Nos,

Yeah, the bottom of the leg will be coming off in the not too distant future for it's biannual pump check, but there is absolutely no "tell tale" in the conventional sense of a jet - It's just like my 1972 'rude - a spray of water out the idle exhaust port, which does get stronger when it's revving. I've checked all round the bottom casing - absolutely no extra holes (blocked or otherwise) for a sideways squirting tell tale.

I chuck this in as a thought - would the primary default exit route not be the telltale - otherwise you'd never know if it was pumping or not until it was too late. I never rev it (other than the odd blip) when it's not in the water, so can't comment on the volume exiting through the prop... what I can say is that at idle it doesn't appear to be any different to any other O/B i've seen being flushed.


Also in repy to jyaski's comments - would the holes in the front of the leg maybe to give some "ram assist" when you're moving fast through the water? Not sure just how much pressure it would add to the system tho'. Probably not a lot.

[Nos4r2]

Originally Posted by 9D280

Nos,

Yeah, the bottom of the leg will be coming off in the not too distant future for it's biannual pump check, but there is absolutely no "tell tale" in the conventional sense of a jet - It's just like my 1972 'rude - a spray of water out the idle exhaust port, which does get stronger when it's revving. I've checked all round the bottom casing - absolutely no extra holes (blocked or otherwise) for a sideways squirting tell tale.

I chuck this in as a thought - would the primary default exit route not be the telltale - otherwise you'd never know if it was pumping or not until it was too late. I never rev it (other than the odd blip) when it's not in the water, so can't comment on the volume exiting through the prop... what I can say is that at idle it doesn't appear to be any different to any other O/B i've seen being flushed.

No-the primary route will always be the prop as it's the route that can handle the most flow. If that wasn't the case then if the comparatively small hole for the telltale (it's only about 5mm round in the water channels in most cases) blocked up then you'd have no cooling.
It's easy to add a conventional telltale-just drill/tap a point on the water jacket and run a hose outside.

[Locozodiac]

Well that will depend mostly on the engine brand, according to my partucular experience some Evinrude/Johnson models have a flush port on the head, A screw must be removed, so not to use a water bucket nor tail water phones to flush. With adecuate water pressure the impeller will be maintained wet when turning and will see water coming out from various parts.

Some brands like Mercury/Mariner/Tohatsu in the smaller engine, example 05 HP can be flushed without running engine, that is, they don't have a thermostat to open, mostly have a flush port on the lower exterior part of the head.

If your engine doesn't have a flush port, a water phone is a must, run engine and flush with adecuate water pressure for at least 5 minutes in fast idle (between minimum and start position) disconect the gas tank, keep engine running until completely stops to consume all gas in carburator bowl.

Put a plastic bag after, so to not mess your house floor with oil being drained from the propeller after flush (2 stroke mainly) Keep engine in a vertical position to drain remaining water.

Botom line: If you have a flushing port use it and run your thermostat engine to keep all salt water off the head inside passages. Your engine will last longer and cool better when running in sea.

[Cookee]

To add to the above post - do not run DFI, Optimax or fuel injected engines out of fuel - only carburettor ones!

[jyasaki]

Originally Posted by 9D280

Nos,
Also in repy to jyaski's comments - would the holes in the front of the leg maybe to give some "ram assist" when you're moving fast through the water? Not sure just how much pressure it would add to the system tho'. Probably not a lot.

Probably not. I assume the leaking-like-a-sieve holes are on the post-engine side of the circuit. As far as I know, from the impeller to the thermostat is a closed tube. Assuming the impeller is working correctly, there's no need for a ram-assist pressurization scheme. It's not an afterburning turbine engine, after all; it's just cooling water.

jky

[jyasaki]

Originally Posted by Locozodiac

disconect the gas tank, keep engine running until completely stops to consume all gas in carburator bowl.

From experience, this may or may not work. My Honda 40 used to get this treatment; I discovered early on that disconnecting the fuel line enabled the dry-break valves in the fuel line connectors, and the vaccuum created is what caused the motor to die, rather than running the float bowls dry.

To actually run the bowls dry, I had to open the fuel line using a pen-tip or similar appliance, and it took forever to use that much fuel at idle.

jky

[bernithebiker]

Originally Posted by 9D280

Nos,



Also in repy to jyaski's comments - would the holes in the front of the leg maybe to give some "ram assist" when you're moving fast through the water? Not sure just how much pressure it would add to the system tho'. Probably not a lot.

I believe yes, quite alot. At speed (15 knots +), the pressure at these water intakes will be considerable, and will help the pump to flow water.

In fact the mechanic at my boat shop reckons that some engines used ONLY this feature to impel cooling water.......not sure about that - what happens at idle?! But if you look at the inlets you will see that they are angled into the flow of water - kind of like water scoops.

[jyasaki]

Originally Posted by bernithebiker

I believe yes, quite alot. At speed (15 knots +), the pressure at these water intakes will be considerable, and will help the pump to flow water.

In fact the mechanic at my boat shop reckons that some engines used ONLY this feature to impel cooling water.......not sure about that - what happens at idle?! But if you look at the inlets you will see that they are angled into the flow of water - kind of like water scoops.

It may help pressurize the system, but the pressure will be static; i.e. will work both for ( pushing water towards the head) and against (pushing water towards the impeller) the desired flow of water.

The openings I refer to (Yam F115) are not "angled" but are simple openings in the lower unit; they are in the forward part of the taper, but I seriously doubt they are designed as ram intakes.

jky

[Locozodiac]

You are right, forgot to mention to disconnect the gasoline hose from the engine connector to consume most of the gas left in the bowl rather than disconnecting from the tank which will take endless time.

To consume the most left in the bowl after the engine has died pull choke again, put grip to full throttle and crank engine untill starts again, push choke and accelerate till engine dies again. Only for carburated engines that are not used on daily basis (eventually)

[jwalker]

Originally Posted by 9D280

I chuck this in as a thought - would the primary default exit route not be the telltale - otherwise you'd never know if it was pumping or not until it was too late.

The primary route for the cooling water exit is into the exhaust down pipe in order to keep the exhaust cool. On all the outboards I've owned, at tickover there isn't sufficient exhaust to blow the water from the main exhaust ways and there were relief holes at the top of the leg; usually covered in some way but not always.

[jwalker]

Originally Posted by Locozodiac

To consume the most left in the bowl after the engine has died pull choke again, put grip to full throttle and crank engine untill starts again, push choke and accelerate till engine dies again. Only for carburated engines that are not used on daily basis (eventually)

What is your view on engine lubrication during this procedure? Since the fuel is the carrier for the lubricant it stands to reason that if you are exhausting the fuel you must be exhausting the engine lubricant too.

[davej]

While I do use the muffs on my old 2 stroke mercury I much prefer to use an old plastic water tank that came out of the loft. I made a cradle with wheels on and usually keep it full of water just ready to run up the OB. This way it is certainly quiet and gives the lower leg plenty of water to stand in as it covers where the pump is situated. It also in my case limits the clouds of smoke generated by a 50:1 2 stroke running on premix. While I have never had problems on the muffs it always concerns me that the hose connection might spring off or maybe someone at home might just switch the cut of valve off inside the house. A tub just eliminates any possibility of that and at home it just pushes out of the way when I have finshed with it. Dead easy to make up.

Dave J

[jyasaki]

Originally Posted by jwalker

What is your view on engine lubrication during this procedure? Since the fuel is the carrier for the lubricant it stands to reason that if you are exhausting the fuel you must be exhausting the engine lubricant too.

Yeah, but you won't run out of lubricant 'til you run out of gas, so when the lube stops, so does the engine. That assumes it's a 2-stroke, of course.

My post on the fuel disconnect was not so much where it was disconnected, as how. On my Honda (40hp 4-stroke), there was a dry-break clip-on fuel fitting at the motor to hose connection point. Disconnecting the hose and waiting for the engine to die would not empty the carb bowls, as the line drew a vacuum well before that. To empty the bowls, you had to sit there and hold the spring-loaded dry-break ball bearing in with a pointed object. Took a while to run dry, too.

jky