Running outboard when flush port disconnected

[smckean (Tosca)]

I've attempted research on this, but I can't find anything other than how to flush your engine.

If one is underway, and, for whatever reason, the hose (or other component) of the flush port breaks or disappears, can one safely continue to run the engine?

My guess would be yes. A heavily leaking flush port would seem to me to be little more than a "second" pee-hole. I wouldn't think enough water would discharge to effect the engine cooling. Besides if the engine did overheat you could tell by the water temp or the overheat alarm that would shut down the engine.

 

[ssobol]

I've attempted research on this, but I can't find anything other than how to flush your engine.

If one is underway, and, for whatever reason, the hose (or other component) of the flush port breaks or disappears, can one safely continue to run the engine?

My guess would be yes. A heavily leaking flush port would seem to me to be little more than a "second" pee-hole. I wouldn't think enough water would discharge to effect the engine cooling. Besides if the engine did overheat you could tell by the water temp or the overheat alarm that would shut down the engine.

Try running the engine on the muffs and disconnect the flush line and see what happens.

 

[smckean (Tosca)]

Try running the engine on the muffs and disconnect the flush line and see what happens.

Good idea. The boat's in the water for a couple weeks; I'll try that when I haul her out.

P.S. This "problem" is not on my boat, but on a friend's Osprey with a 300hp Yamaha. He's not sure if he can run it or not. But then I thought: "You know, I'd like to know the answer to that question too."

 

[Sea Wolf]

I'm thinking the flushing inlet port is mid-stream from the water pump in the lower unit up to the power head.

Leaving that port open will reduce the water flow potential to the power head and the thermostat at the power head outlet into the exhaust stream.

You might think it won't hurt until the engine warms up, the thermostat opens up, and water is needed for cooling.

Will the pump supply enough water to cool the engine with the flushing inlet open? Will it depend on the engine rpm? Or the water temperature supplied by the pump?

What happens if the water supplied and lost out the port leaves the head dry and no hot water reaches the thermostat, and you're just running on a dry power head with no water to help distribute the heat from the hot spots like the cylinder heads?

Who's on second?*

Sounds like Russian Roulette with a ~$30,000 engine at the end of the barrel. :lol:

(* Abbott and Costello)

Your call!

Joe. :teeth :thup

 

[smckean (Tosca)]

All good questions Sea Wolf. You misunderstand. I'm not doing this for fun or to experiment; rather my friend actually had this flushing hose break while he was cruising. The question was could he run his engine to get home and do repairs or not.

I am looking for the "factory" answer to this question. That is, does anyone know what Yamaha has to say about this?

 

[ssobol]

...Will the pump supply enough water to cool the engine with the flushing inlet open? Will it depend on the engine rpm? Or the water temperature supplied by the pump?

What happens if the water supplied and lost out the port leaves the head dry and no hot water reaches the thermostat, and you're just running on a dry power head with no water to help distribute the heat from the hot spots like the cylinder heads?
...

It is possible that the pump can push enough volume that having the flush hose disconnected is not an issue (especially at higher RPMs).

 

[thataway]

Too risky to loose that volume of water. I would not run home. Very easy to fashion a "plug" of wood to block the hose--and always carry spare hose clamps. Any boat with a thru hull, should be carrying tapered plugs. Not a bad idea to carry some small pieces of wood on any boat--can be useful in many ways.

 

[smckean (Tosca)]

Too risky to loose that volume of water. I would not run home.

Bob, would you still consider it too risky if you kept an eagle eye on the water temperature gauge, and if you saw the engine temp rising significantly, shutting the engine down -- putting you in the same situation you would have been in if you hadn't attemptted to run the engine after the failure of that flush port?

Later edit.....I guess this raises another question. If no water is getting to the engine head, will the temp gauge, or engine alarm, register the over heating engine? I would presume so since surely the engine designers wouldn't put you in the situation that the engine overheating alarm doesn't protect you if you, say, lose your water pump.

 

[hardee]

Not the answer you are looking for, but related.

At one time, a ways back, there was a thread about using the flush port water off the Yami OB's for a source for warm water for an onboard shower.

Your question seems very pertinent to that use, and was not brought up in that thread. I know there were several who did a modification to the port fur that purpose, but I do not recall much followup on that thread, especially regarding any obvious adverse affects.

Harvey
SleepyC :moon

 

[Ron on Meander]

Well.... don't know if it was risky or not but I ended up running for more than an hour with the flush port disconnected due to a "senior" moment. This was several hundred hours ago and I haven't seen any noticeable problems. I did not get any engine overheat alarms or notice a temp rise. So I would think it can probably handle it. Just wish the "senior moments" weren't so frequent these days.

Cheers
Ron :crook

 

[thataway]

Too risky to loose that volume of water. I would not run home.

Bob, would you still consider it too risky if you kept an eagle eye on the water temperature gauge, and if you saw the engine temp rising significantly, shutting the engine down -- putting you in the same situation you would have been in if you hadn't attemptted to run the engine after the failure of that flush port?

Later edit.....I guess this raises another question. If no water is getting to the engine head, will the temp gauge, or engine alarm, register the over heating engine? I would presume so since surely the engine designers wouldn't put you in the situation that the engine overheating alarm doesn't protect you if you, say, lose your water pump.

To answer your question--I have see the "overheat" alarm go off when water intake plugged by plastic bag. So it should go off if over heating when no water was getting to the top passages.

If you have a temp gauge that puts it in a bit of a different category than waiting for the engine over heat alarm....I certainly would run the engine slowly, if it was not possible to fix the. issue on a temporary basis...

 

[ssobol]

FYI. I was running my Honda BF90D on the muffs after some engine maintenance. Just for grins I disconnected the flush port hose from its stowed position. No water came out of the flush port. There was no change to the amount of water coming out the pee hole.

 

[Sea Wolf]

FYI. I was running my Honda BF90D on the muffs after some engine maintenance. Just for grins I disconnected the flush port hose from its stowed position. No water came out of the flush port. There was no change to the amount of water coming out the pee hole.

Do you suppose there's a check valve in there?

(Red highlighting mine.)

Joe. :teeth :thup

 

[smckean (Tosca)]

My boat is still in the water until later this week, so I haven't yet tried the "ear muffs + disconnect" test; however, while out on the boat at the end of last week, I did a quick test.

I disconnected the flush port hose and re-started the engine. I disconnected the prop at the throttle control, and set the RPMs at 1000. I ran it like that for maybe 10 minutes. I was a bit surprised at the volume of water that shot out of the port; if I had to guess, I'd say 3 times the volume that typically comes out the pee hole. I did not notice any problems. The pee hole volume dropped a bit, but not much. I kept an eye on the water temp gauge and did not see any rise in water temp (my water temp gauge displays a marker along a horizontal bar -- standard Yamaha gauge setup). The gauge is not good for showing small changes in temperature, but if the temp had risen significantly, I think I would have seen some evidence of that. Since I do hull speed at 1300 RPM, I think I could get home if that flush port were badly leaking.....but I'd have an eagle eye on the water temp gauge.

P.S. I attempted to call Yamaha tech support to ask the question. I had just explained the situation, and was starting to get the feeling that I was going to get one of those "we don't recommend it" type answers, when, believe it or not, some sort of fire alarm went off in their building. The tech lady had to hang up and evacuate, so I never did get an answer.

 

[Sea Wolf]

(Some clipped)

P.S. I attempted to call Yamaha tech support to ask the question. I had just explained the situation, and was starting to get the feeling that I was going to get one of those "we don't recommend it" type answers, when, believe it or not, some sort of fire alarm went off in their building. The tech lady had to hang up and evacuate, so I never did get an answer.

They were probably running a motor with the flush hose port open to test the theory that it wouldn't make any difference when the engine alarm went off, indicating an overheat condition. :lol:

Olde West Addage:"If ya like to shoot yerself in the foot, go ahead, it's an easy target, and satisfaction is guaranteed!" :wink

Joe. :teeth :thup

 

[thataway]

The engine would heat up more under load--that is with the prop engaged, and the engine at the RPM for "cruise". This is why it is always recommended when running the engine for maintenance purposes, that it be in gear to put a load on it. How much know--we don't know. Perhaps an IR thermometer on the cylinders or heads would help answer the question...

 

[tsturm]

Too risky to loose that volume of water. I would not run home. Very easy to fashion a "plug" of wood to block the hose--and always carry spare hose clamps. Any boat with a thru hull, should be carrying tapered plugs. Not a bad idea to carry some small pieces of wood on any boat--can be useful in many ways.

:thup Thank you! Common sense is becoming more & more un common. :roll: