Start boat diesel with water hose in inlet?

[quartersplash]

I have a large boat on a trailer that I just purchased and it has a 16 HP Yanmar. I don't want to put it in the water yet but I want to start the engine to make sure all is well. Is it ok to stick a water hose in the thru hull and start it? If so, I am assuming I don't want a lot of pressure? Thanks

[malbert73]

NOOO!!
Put the water hose in a bucket. Put a hose for the raw water inlet in the same bucket.
What you are proposing could fill your engine with water

[barnab]

Finding the balance between not-too-much-pressure and enough water will be hard. I would do one of these:
- Open the strainer and keep the strainer filled with a hose
- Disconnect the suction hose from the seacock and put it in a bucket
- Install a T-valve in the suction side of the raw water pump to switch easily between sea water and bucket


I would go for (1)

[s/v Jedi]

To make it clear for a new owner: at the inlet, close the seacock (valve) so no water can run out. Then find the sea strainer which is a filter between the engine and the valve. It will have a lid, remove the lid and fill with water from a hose. Then while someone starts the engine and check everything, another person keeps filling the strainer from the hose.

For Groco strainers you can buy a lid with a hose connection to make this easy and eliminate one person needed.

[CaptTom]

For your Yanmar you ought to be able to keep the strainer filled with a garden hose. Be ready to shut it off before it runs dry, until you know for sure that the hose can keep up.

For anyone with larger motors, understand that some of these things move a lot of water. Far more than a hose can provide.

[Lou-In-NJ]

Originally Posted by malbert73

NOOO!!
What you are proposing could fill your engine with water

I think what malbert is talking about is that raw water marine engines put the the cooling water into the exhaust and use the exhaust presures to expel the "coolant" water through the wet muffler. So if you pressurize the water inlet without the engine first running, you could fill your exhaust system to the point of flooding your cylinders through the exhaust valves. Theoretically this is possible if you don't start the engine immediately after hooking up the pressurized hose, but you have the water pump impeller slowing down the water when the engine isn't running, and the thermostat is closed on a cold engine, further restricting the water flow. Also, if you're only going to see if the engine can start and run for a minute or two, you don't need to worry about cooling it for a brief run. However, I would make sure the raw water pump is working before putting the boat in the water, by pulling the water inlet hose off of the seacock, and putting it in a bucket of water to make sure the pump draws water when the engine starts. It should draw water immediately, even while the engine is cold.
Finally, if you don't know how old the water pump impeller is, change it!
...I've seen a couple of people, over the years, blow their engine as it overheated pulling into the marina.

[capt jgw]

You can run the engine FOR A FEW SECONDS without water just to make sure it starts. I usually do this while waiting for the travel lift to come for launch. This will not tell you if the water pump works though. If you take the raw water pump impeller out (which I usually do for winter storage) you can run it for a minute or two. It will not make enough heat in that time to hurt anything. Once again, running it that way will not diagnose the cooling system. To run it longer you'll have to supply it with water from a bucket as said above. Letting the pump suck the water out of the bucket will tell you the pump works, force feeding it will not and could hydrolock the engine.