'90 Merc 100hp no water

[olsenk514]

I have a 1990 merc 100hp that I just bought. Took it home and started it up and i'm not getting any water out of the "pee hose." Figured it was an old destroyed water pump so I got a new pump kit and replaced everything. I'm still not getting anything through the cooling system.

I took the lower unit back off and put a hose directly where the pump pushes water up and it seems like it's not getting past the mid section. Not really sure if the water tube is out of place near the powerhead or what. If I blow air up that same tube I can feel some of it coming out the pee hole, but not a lot.

Do I have to remove the midsection to get to the top of the water tube? or is there an easier way?

 

[Damien.]

Re: '90 Merc 100hp no water

Check the stat's are working in a pot of boiling hot water.

Its not uncommon for these to fail.

 

[olsenk514]

Re: '90 Merc 100hp no water

I actually just read that somewhere. Wouldn't I still get a stream though? Or would a stuck thermostat block the water completely??

 

[verado7]

Re: '90 Merc 100hp no water

siezed i smore like the word for a t-stat but yes it would block the water - you didnt get an overheat alarm - did you run it long enough ? some wont "pee" until pressureand volume builds - mine is like that and it's normal - fire it up - and count to 40 - you should see something by then - even fast idle to 1200 rpm in neutral . if nothing shows check the thermostats first - a winter storage is enough to sieze them after a season or 2 in the chuck maybe a year or 2 longer in fresh water .

 

[olsenk514]

Re: '90 Merc 100hp no water

siezed i smore like the word for a t-stat but yes it would block the water - you didnt get an overheat alarm - did you run it long enough ? some wont "pee" until pressureand volume builds - mine is like that and it's normal - fire it up - and count to 40 - you should see something by then - even fast idle to 1200 rpm in neutral . if nothing shows check the thermostats first - a winter storage is enough to sieze them after a season or 2 in the chuck maybe a year or 2 longer in fresh water .

Thanks verado. I didn't want to run it too long without water going through. If I remove the tstat will and start it up will I see water coming out? Thanks

 

[sschefer]

Re: '90 Merc 100hp no water

The tell tale on your engine gets it water directly from the fitting on the exhaust cover on the port side of the engine.

Remove the tube and the fitting and make sure they are clear. It's probably just a piece of dirt in the tube.

Worst case scenario is the Exhaust diverter plate gasket blew out and a piece of it is blocking the tell tale outlet.

The important thing to remember is that exhaust cooling always takes place but cylinder cooling regulation is controlled by the Thermostats and Poppet valve.

On your engine the tell tale is on the exhaust cover plate so water should flow within a few seconds after starting.

 

[olsenk514]

Re: '90 Merc 100hp no water

I actually have the telltale hose completely off. The little plastic piece at the end that spits the water was clogged but I'm still getting nothing. Right now it's just the little elbow that comes out of the exhaust plate on the port side. When I blow air down from the top I get some out the water tube (l/u removed) and some out the 3 small exhaust ports. Not sure what to try next...

 

[sschefer]

Re: '90 Merc 100hp no water

There should be a 3/8 plug on the cylinder cover for back flushing the motor. Make up a fitting to accept a garden hose and using light to moderate pressure, back flush the engine without it running. Don't use too much pressure, just enough to get the job done.

Just out of curiosity, is the engine running o.k. otherwise? No shinny piston tops or super clean plugs?

 

[olsenk514]

Re: '90 Merc 100hp no water

There should be a 3/8 plug on the cylinder cover for back flushing the motor. Make up a fitting to accept a garden hose and using light to moderate pressure, back flush the engine without it running. Don't use too much pressure, just enough to get the job done.

Just out of curiosity, is the engine running o.k. otherwise? No shinny piston tops or super clean plugs?

I wasn't able to find a plug anywhere There is a 3/8 elbow that the tell-tale hose comes off of, but no plug.

Anyways...I removed the exhaust cover that's over the cooling passages. Figured I should change the gaskets anyways. I only ended up breaking 2 bolts out of 20 something. There's nothing I can see clogging anything.

There are 2 separate 'sections' in the cooling system...one looks like it cools the exhaust area? and the other goes to the cylinders and then out the telltale. When I shoot water up the water tube with the hose, it comes into the cooling passages surrounding the exhaust, but nothing comes into the cylinder cooling passages. I'm not sure how it's routed after the water tube, but I'm not sure how water is supposed to get into the cylinder jacket???

There's a small hole for water to enter but i squirted some down there and it comes out the exhaust.

Thanks for the help guys. I'll get this thing running sooner or later

 

[verado7]

Re: '90 Merc 100hp no water

yes if you remove the stats water will come thru if the pump is working properly .