Water pump works then stops after a few minutes, old Yamaha 6b 678.

[southampton_mike]

Hi All

I`m new to boating, I`ve just bought a Small rib and Yamaha 6b 678 6hp outboard (I think I may have made a bad purchase). When I start the engine the water pumps fine from the tell-tale on idle, however when I put it in gear after a couple of minutes the flow pretty much stops to a splutter and started to steam, I shut the engine straight off to not cause any damage or further damage. I tried the engine again last night and the same thing happened. The impeller looks OK however i`m going to change it anyway. I cant seem to be able to find a water pump for sale for this engine to replace the whole thing.

Do you think this would be the cause or is there anything else you think this may be?

Thanks in advance for any help.

Mike

 

[VicS]

Hi All

I`m new to boating, I`ve just bought a Small rib and Yamaha 6b 678 6hp outboard (I think I may have made a bad purchase). When I start the engine the water pumps fine from the tell-tale on idle, however when I put it in gear after a couple of minutes the flow pretty much stops to a splutter and started to steam, I shut the engine straight off to not cause any damage or further damage. I tried the engine again last night and the same thing happened. The impeller looks OK however i`m going to change it anyway. I cant seem to be able to find a water pump for sale for this engine to replace the whole thing.

Do you think this would be the cause or is there anything else you think this may be?

Thanks in advance for any help.

Mike

I dont think you will find a complete water pump . All parts were available separately and I believe overhaul kits ( with or without the housing ) are available from non OEM suppliers such as Sierra)

You may have trouble due to blocked cooling passages which may need a powerhead removal and cylinder head off to unblock

Also worth checking the thermostat

You may find the manual at http://www.boatinfo.no/lib/yamaha/manuals/1984-1996yamaha.html#/0 useful

 

[southampton_mike]

I dont think you will find a complete water pump . All parts were available separately and I believe overhaul kits ( with or without the housing ) are available from non OEM suppliers such as Sierra)

You may have trouble due to blocked cooling passages which may need a powerhead removal and cylinder head off to unblock

Also worth checking the thermostat

You may find the manual at http://www.boatinfo.no/lib/yamaha/manuals/1984-1996yamaha.html#/0 useful

Thank you, I’ve been struggling to find a manual. I’ll definitely check the thermostat and If the impeller doesn’t fix it I’ll look into the other possibilities.

 

[southampton_mike]

Thank you, I’ve been struggling to find a manual. I’ll definitely check the thermostat and If the impeller doesn’t fix it I’ll look into the other possibilities.

I dont think you will find a complete water pump . All parts were available separately and I believe overhaul kits ( with or without the housing ) are available from non OEM suppliers such as Sierra)

You may have trouble due to blocked cooling passages which may need a powerhead removal and cylinder head off to unblock

Also worth checking the thermostat

You may find the manual at http://www.boatinfo.no/lib/yamaha/manuals/1984-1996yamaha.html#/0 useful

hi just thought I’d give you an update. The impeller was fine but it’s now replaced anyway, the thermostat was missing. You were spot on that there was a blockage the wholething was full of salt/corrosion/sand. Removed and cleaned out the best I can and it seems to be running ok. Haven’t tested it out on the water yet. The link to the manual didn’t work.

 

[Web0r]

How did you manage to clean the cooling canal? Did you clean it all or only around the thermostat? We have the same old engine but the whole system does not cool at all, the previous impeller was shredded in pieces so perhaps it’s blocking the tube but i’m a bit unknowing on how to attack the problem and where to start.

 

[VicS]

hi just thought I’d give you an update. The impeller was fine but it’s now replaced anyway, the thermostat was missing. You were spot on that there was a blockage the wholething was full of salt/corrosion/sand. Removed and cleaned out the best I can and it seems to be running ok. Haven’t tested it out on the water yet. The link to the manual didn’t work.

Thanks for the feed back

The link to the manual works OK for be , but Ive checked on the model and yours predates the manual so it was bum steer anyway

 

[southampton_mike]

How did you manage to clean the cooling canal? Did you clean it all or only around the thermostat? We have the same old engine but the whole system does not cool at all, the previous impeller was shredded in pieces so perhaps it’s blocking the tube but i’m a bit unknowing on how to attack the problem and where to start.

Hi yeah I took the casing off and cleaned as much as I could get to. snapped a few of the bolts though that had corroded as wellbut still had enough to hold the casing back on correctly. Once cleaned the water flowed through well but the I obviously caused a different issue where the engine would cut out when throttled up. I have since sold the engine on as I could see it becoming a money pit at this age. Sold as spares or repairs on eBay and it sold for over £300 I was very surprised.