Merc 150 V6 Cooling - is this correct?

I have a 150 V6 Merc (1981) - when its ticking over I get no water from the pisser or the two exhaust ports.

When I run it at 3,000 RPM in neutral (or in FWD) water comes out of the exhausts (pretty warm to the touch but not hot)

Regardless of throttle no water comes out of the pisser - I have blown down it with the air line and its clear - any ideas?

The engine doesnt appear to be overheating, however I can only run the engine flat out for 60 seconds in either direction on the water I'm testing on (River) before I need to stop and turn around - but no alarm is sounding - would it get hot enough to set it off doing this?

Is this normal - if not what should I change.

I fitted a new impeller a couple of weeks ago - could I have misaligned the main water pipe or somthing? Thermostats are OK - I checked they moved in hot water, cant I just remove them? - My Jetski runs without thermostats and has great pressure from cold.

Thanks for ALL and ANY help.

Jim

Re: Merc 150 V6 Cooling - is this correct?

you may want to check to see if the top of the water tube is in the bottom of the powerhead correctly. was there any water coming out of the telltale at all before you worked on it?

Re: Merc 150 V6 Cooling - is this correct?

you can also remove the thermostats and run the motor to see if there is water flow. if it's a weak flow check the poppet valve diaphram

Re: Merc 150 V6 Cooling - is this correct?

latin monkey said:

you may want to check to see if the top of the water tube is in the bottom of the powerhead correctly. was there any water coming out of the telltale at all before you worked on it?

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I'm not sure as I purchased it and stripped to change right away - he had it running on a hose and there was water from the pisser, but I dont have the flush bellows to try a comparison. Would the hose pipe & bellows force more water through the motor than the impeller alone hence why it did then but doesnt now?

When I refitted the lower unit I was careful to line up the main shaft and gear shift - thought the pipe for cooling would line itself up - is that not the case?!?

Thanks.

Re: Merc 150 V6 Cooling - is this correct?

the water tube needs to go in just right. there is a small grommet that it fits into just like it does in the water pump housing. i install the water tube into the powerhead first then align it into the water pump housing as i raise the lower unit.

Re: Merc 150 V6 Cooling - is this correct?

latin monkey said:

you can also remove the thermostats and run the motor to see if there is water flow. if it's a weak flow check the poppet valve diaphram

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Any reason why I cant just bin the thermostats and run it without?

Re: Merc 150 V6 Cooling - is this correct?

yes you can run it without them. thermostats help the motor warm up faster

Re: Merc 150 V6 Cooling - is this correct?

latin monkey said:

yes you can run it without them. thermostats help the motor warm up faster

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Some engines will cold seize if powered up when cold. this engine will normally warm up to full temp in about 20 seconds with thermostats, and stay there. Without them, you have all kinds of issues, from fuel mix to the above said seizing problem.

Put the engine on the cups, remove the thermostat housings and thermostats, and start it up. Within 20 seconds you should have a pretty generous flow of water out the holes. If not, you have problems in water pump or delivery tube. If you do, then the telltale is plugged. I've seen a small stone plug em up, and not clear with air. Had to pull the hose off and flush it out.

The most useful information on the condition of your cooling system would come from a water pressure gauge.

hope it helps
John

Re: Merc 150 V6 Cooling - is this correct?

As J_martin suggested, a pressure gauge is a very good way to monitor and diagnose the cooling system. Also, the below linked guide can give you an idea as some common water pressure conditions and possible causes.

http://forums.iboats.com/attachment.php?attachmentid=26018&d=1239382120