Merc 1976 tower of power won't pee but does puff air.

[Bass_o_matic]

Just replaced the impeller and gaskets, and also tried fishing the waterline with weedeater line but it still only puffs. The old impeller was falling apart so it could be debris, but at the same time it's puffing air so I don't know if the water just isn't even making it to the impeller. Any help would be great!

 

[wired247]

Re: Merc 1976 tower of power won't pee but does puff air.

"fishing the waterline with seadeater line but it still only puffs"

What?

 

[Bass_o_matic]

Re: Merc 1976 tower of power won't pee but does puff air.

Fat thumbs. Weedeater line.

 

[wired247]

Re: Merc 1976 tower of power won't pee but does puff air.

I had to read that a few times to figure out what you were talking about. So you cleaned out the pee hole with string. Got it. It might not be pump related. You could have a blown fuel pump diaphragm that is pushing crankcase pressure into the water chest. Could be a exhaust/water gasket blown on the port side exhaust chest. Theres quite a few places on those inlines for water and crancase or exhaust gasses to come into contact with each other if the gasket is bad. If you run it on the muffs do you have water coming out the lower where the prop is?

 

[racerone]

Re: Merc 1976 tower of power won't pee but does puff air.

How does a bad diaphragm " push crankcase pressure into the waterchest "-----explain please.

 

[wired247]

Re: Merc 1976 tower of power won't pee but does puff air.

I know. It doesnt make sense but on many of the early 70's ( after '73 ) the fuel pumps were water cooled. If the diaphragm ruptured it would push crankcase pressure into the water jacket.. Ive owned a few of those blocks and generally just plug the water port to the fuel pump.

 

[Chris1956]

Re: Merc 1976 tower of power won't pee but does puff air.

Water cooled fuel pumps? What motors were those on?

I had a '77 Merc 1500. The fuel pump sucked, but was certainly not watercooled. I would think on that motor, that exhaust could back up into the cooling system, as they mix at the base of the block. Likely the OP has a piece of old impeller plugging the water tube. Maybe a thin piece of stiff wire can remove it.

 

[wired247]

Re: Merc 1976 tower of power won't pee but does puff air.

Water cooled fuel pumps? What motors were those on?

I had a '77 Merc 1500. The fuel pump sucked, but was certainly not watercooled. I would think on that motor, that exhaust could back up into the cooling system, as they mix at the base of the block. Likely the OP has a piece of old impeller plugging the water tube. Maybe a thin piece of stiff wire can remove it.

'73 up to early '75 blocks had water cooled ( or heated ) fuel pumps. I know. It sounds weird but there is a water passage right through the water pump diaphragm area that feeds from the cylinder water chest. Later blocks have the cavity with no water connection. If the diaphragm blows you'll get water intrusion into the crank case or the other way around.

 

[jimmbo]

Re: Merc 1976 tower of power won't pee but does puff air.

Never heard of a water cooled fuel pump on the inline 6. There were some on either the 3 cylinder or the 402 3 cylinder

 

[wired247]

Re: Merc 1976 tower of power won't pee but does puff air.

Never heard of a water cooled fuel pump on the inline 6. There were some on either the 3 cylinder or the 402 3 cylinder

Not making it up. Ive owned 3 of them. All '73 and '74. I just plug the water port from the cylinder cover to the fuel pump cavity..

 

[CharlieB]

Re: Merc 1976 tower of power won't pee but does puff air.

Are you SURE the water transfer tube plugged into the water pump while you raised the LU?

When you had it running did you place you hand on the exhaust side cover, and was it cooled?

Make sure of these things first. Then if you have access to an air compressor try blowing back thru the P tube, or see if you can hook the water hose to it and back flush it.