running motor with no lower unit. 2.5 merc.

[derekfl]

a 5/8 ths hose slides right on the copper water tube. i assume that i can run the motor that way with a shut off valve on the hose to regulate water flow. real question: can i run water through the motor without the motor running to check water flow? or will it fill the exhaust cavity and back-fill the combustion chambers with water? i am thinking one could start with a bare block or powerhead and plumb water into it and see it travel up and into the heads. then close them off and watch water flow to the next point, etc.

[rjdubiel]

you can, but too much pressure can push the copper pipe out of the adapter plate. Doesnt need to run to flow water.

[25two.stroke]

I run the motors like that all the time. But just like he said above...water will flow through the powerhead whether the motor is running or not.

[pcrussell50]

I run the motors like that all the time. But just like he said above...water will flow through the powerhead whether the motor is running or not.

Won’t be hot enough to open the thermostats and might not be enough pressure to be able to push the thermostats open though, right? So you might not get a full picture of the flow.

-Peter

[David - WI]

Thermostats open fully in a coffee mug of hot water.

[derekfl]

I run the motors like that all the time. But just like he said above...water will flow through the powerhead whether the motor is running or not.
if water is flowing and motor not running, will it fill with water like a 4 stroke? or is there so much exhaust reversion in a 2 stroke the water has to be kept far downstream from the exhaust ports?

[transomstand]

if water is flowing and motor not running, will it fill with water like a 4 stroke? or is there so much exhaust reversion in a 2 stroke the water has to be kept far downstream from the exhaust ports?

It's an open cooling system. Turn on the hose and it will piss water out everywhere.

[derekfl]

so it will fill up the exhaust ports and thus the pistons with water? or just run out the bottom? i have a bad 2.4 that is together enough to use as science fair project and dead enough to not care if it gets wet...

[transomstand]

so it will fill up the exhaust ports and thus the pistons with water? or just run out the bottom? i have a bad 2.4 that is together enough to use as science fair project and dead enough to not care if it gets wet...

How does water get to the exhaust ports?:confused:

[derekfl]

in a chevy v8, the exhaust gas mixes with the water AT SOME POINT!. it has to be a certain distance downstream from the exhaust valve depending on cam profile. the longer duration and more overlap the farther the motor can suck water back in exhaust at idle. therefore the farther the manifold has to keep the two separate. some dump the water after using it to surround exhaust without mixing at all. makes for a very loud engine. the 2 stroke has "valve" overlap like nothing else i can think of. is water mixed with exhaust in the exhaust chest or is it down in the adapter-tuner-mid section?

[25two.stroke]

in a chevy v8, the exhaust gas mixes with the water AT SOME POINT!. it has to be a certain distance downstream from the exhaust valve depending on cam profile. the longer duration and more overlap the farther the motor can suck water back in exhaust at idle. therefore the farther the manifold has to keep the two separate. some dump the water after using it to surround exhaust without mixing at all. makes for a very loud engine. the 2 stroke has "valve" overlap like nothing else i can think of. is water mixed with exhaust in the exhaust chest or is it down in the adapter-tuner-mid section?

BS. You can run any chevy v8 on a pallet with a water hose hooked up to it and it won't suck water back into the engine. open exhaust manifods doesn't matter. Same with a 2stroke outboard or a 4stroke outboard. You can run them all with no lower unit and it will not cause any water intrusion. The only ones you can't run with no lower unit is a 4stroke that has the oil pump driven off the driveshaft splines not off the cam. Those will have no oil pressure if you start them with no lower. If you get water sucked back in the exhaust something is wrong. The only inboards I can think of that would do that are ones with imco, hardon or aftermarket manifolds that mix water on the uphill side of the exhaust, but thats pretty rare.

[pcrussell50]

...water will flow through the powerhead whether the motor is running or not.







Thermostats open fully in a coffee mug of hot water.

sure but a garden hose should not be hot enough for that, right?

-Peter

[25two.stroke]

No. Those thermostats should open @ 143 deg F and I don't think garden hose water is that hot even in hot as h*** florida. But if you turn the water on just enough and DO run the motor you can get it up to temp. But you have to only turn it on to 5 or 6 psi...makign sure the poppet doesn't open and dump all the water out.

[derekfl]

yes jason you can run an engine with a hose. if you run the hose through the chebby V8, it better be running. running a hose through a non-running engine MAY fill the exh manifolds with water and have it dump into the combustion chambers or fill up on the exhaust valves and drop onto piston as soon as you crank it. i am wondering about flushing the cooling system without running the engine. mainly to check it for water flow and lack of obstructions before buttoning it up.

[donmac]

start the motor before turning water on, shut water off before stopping the motor! same as any engine with wet marine manifolds shop testing. your not dynoing it so doesn't need a lot of water!
I always brought them to temp and tore down obstructions like turbo's/chillers/manifolds for retorquing head bolts much faster/easier than doing it in the boat! those days are gone with torque to yield bolts!

there isn't much you can't see in an outboard block tore down, can't remember if 2.5 has rubber divertors in water jacket like 2.4!

[matt83]

yes jason you can run an engine with a hose. if you run the hose through the chebby V8, it better be running. running a hose through a non-running engine MAY fill the exh manifolds with water and have it dump into the combustion chambers or fill up on the exhaust valves and drop onto piston as soon as you crank it. i am wondering about flushing the cooling system without running the engine. mainly to check it for water flow and lack of obstructions before buttoning it up.

Nah, you can turn on the hose on, and let water flow until you flood the driveway with a bbc, sbc, or ford with out the engine running. If water gets into a cylinder you have a problem. Cracked or corroded manifold. The only time v8s suck water in is when something is broke/cracked or rotted out. Overlap with a big cam is possible, but thats when you just run dry to the tip or dry all the way, but the exhaust is still water jacketed.

[transomstand]

Well, I see I made an error. I was under the mistaken impression I was answering a question about V-6 Mercury outboards. Instead I'm getting "educated" about car motors.

Still can't figure out what in the holy hell a horizontally mounted Chevy has to do with a vertically mounted Merc powerhead.

I'll be more cautious in the future with my answers.

For now, the only reasons to get water in the exhaust ports are: Blown head gasket, blown base gasket, cracked block, divider OR THE GODDAM BOAT IS SINKING.

And people wonder why guys don't post anymore...........

[derekfl]

i am asking about running water through a v6 without running the motor. will it flood the motor or drain out the bottom? i was using my experience in a previous life as reasons why i am worried. but i am just gonna put a bad powerhead on top of the adapters and fire up the hose and see where the water goes and where it may wanna stop.

[InjectorService]

Holy cow man, whats all the fuss about.

To the OP, hook the damn hose up, put a little water on and run it. By the time the water and exhaust mix they are long past the point of going back into the engine.

[25two.stroke]

i am asking about running water through a v6 without running the motor. will it flood the motor or drain out the bottom? i was using my experience in a previous life as reasons why i am worried. but i am just gonna put a bad powerhead on top of the adapters and fire up the hose and see where the water goes and where it may wanna stop.

You are safe to do so. You can also look up very detailed water flow diagrams in the service manuals and on google.
I added extra info to my posts to potentially help other people years down the road who may come across this thread with a similar question on a different engine.