out of water running

[Frank mellin]

I have a Fletcher fitted with a mercruiser inboard engine and an alpha one outdrive.
I want to run the engine whilst out of the water to check everything before putting it in water
Problem I have is where the boat is stored I have no access to running water and to provide a tank large enough for the out drive would be approx 200 ltrs.
I am thinking of setting up a sealed system from the muffs to the water outlet from the boat using a header tank of approx 50 ltrs.
Seems a simple solution but am I missing something

 

[Mr Googler]

Muffs are not water tight and it will run out of the leg. Muffs rely on 2 bar of mains pressure to get water to the impeller (which is quite a long way away compared to an outboard) which then sucks it up round the engine.

It would work if you piped in just before the impeller on the engine though.

 

[Frank mellin]

thanks for the info.
just a couple of questions.
you mention that muffs need 2 bar of pressure but surely when boat is in water the pressure supplying the leg is only the normal intake water pressure.
If I mounted the header tank level with boat deck the water should prime itself to the impeller?
As mentioned I am thinking in the dark on this so any help appreciated

 

[Mr Googler]

As said…the muffs aren’t water tight. In the drink…water is already up inside the leg intake pipe work so the suction effect of the impeller is effective at pulling it the rest of the way.

Not so with muffs hence you need some pressure behind and lots of flow. Maybe not 2 bar but you get the idea.

You could always try your way…if you don’t get water coming out in 15 seconds…that’s your answer ?

 

[Frank mellin]

OK ,thanks for the explanation
Maybe I should try to find a suitable water supply by taking the boat elsewhere or just put it in the water first.
One thing I dont want to do is ruin the impeller, I managed to do that on an outboard engine last year by running it dry for 5 mins!
Appreciate your help though, many thanks.

 

[Mr Googler]

What engine model is it?

 

[Frank mellin]

its a 140hp mercruiser inboard

 

[ChromeDome]

I had same situation and used a rainwater barrel with sufficient diameter. It was higher than needed but was cut on one side to fit the drive. Despite a tank capacity of 200 litres I only filled it to a couple of inches above the intake holes in the leg. Worked fine.

For winterization I used a can on the bathing platform, a hose and muffs. Gravity apparently was enough to make it work, ran it until coolant mix came out with the exhaust (not many seconds btw) .

 

[BruceK]

As said…the muffs aren’t water tight. In the drink…water is already up inside the leg intake pipe work so the suction effect of the impeller is effective at pulling it the rest of the way.

Not so with muffs hence you need some pressure behind and lots of flow. Maybe not 2 bar but you get the idea.

You could always try your way…if you don’t get water coming out in 15 seconds…that’s your answer ?

IIRC the impeller is in the leg of a MR/ Alpha 1 right? Ergo a 1/4 44 gal oil drum or a B&Q wheelie bin cut down to size to fit under the drive would suffice. Would only need 50 litres or so. Stop when the water in the drum gets hot.

 

[Mr Googler]

IIRC the impeller is in the leg of a MR/ Alpha 1 right? Ergo a 1/4 44 gal oil drum or a B&Q wheelie bin cut down to size to fit under the drive would suffice. Would only need 50 litres or so. Stop when the water in the drum gets hot.

funny enough….I was trying find a picture of the impeller pump on the engine but it was only on the bigger mercruisers so read up alpha one and you’re right….impeller in the leg ?

@Frank mellin ….don’t take advice on a boating forum from people who are arm chair experts at best….i.e ….me ??

 

[Frank mellin]

thanks guys, armchair or not you took the trouble to advise me.
really appreciate that