[davemross]

my father in law just got a 20 horse mercury thunderbolt (early 70's model). The owner said that the motor had been in his garage for a couple of years and that we would probably need to change the impeller...so we bought a new one and installed it but the motor still wont pump water...anyone know what might be wrong the key is in correctly but no water seems to be flowing..looked for a thermostat but couldnt find it please help.

[baconbiscut]

did you make sure the impeller key was in. Also the impeller has to spin in a clockwise position it could be possible that the blades were turned the wrong way during installation

[davemross]

yes the key is in correctly, weve had the lower unit off probably 3 times trying to figure out what the problem is...do you know if that model has a thermostat or does the pump run constantly? thanks

[greg23]

did you replace all the gaskets?Mabey you should get a new water pump housing.

[green4themoney]

the older ones do not have thermostats, ok forst of all, your tell tale hole may just be plugged, so remove the hood, and find where the water exit hose leaves the motor and take that right off the water outlet from the engine to the exterior fitting of the engine, so you have the hose in your hand, check it to make sure its not clogged or anything and check the 2 fittings you just took the hose off of to make sure they arent clogged (those mud dabbers can get in there and be a pain) try running the engine without that hose shortly, see if it squirts out the fitting that comes off the engine. if it fails to do this, we have a block/ leak somewhere else in the engine and your going to have to drop your lu, first things first, make sure you have your impeller blades set so that the driveshaft spins clockwise, check your pump housing and your water tube seal (that sits right in the top of the pump housing and initially seals the water tube to the pump housing), you can even dunk the LU in a barell of water and hook a drill up to the driveshaft and spin it with the pump under water to se if its pumping properly, also hook a hose up to your water tube and run water through your engine block, when you do this, is should take a few seconds to fill up then you will see water start to fal down your driveshaft housing and it will start to come out of the telltale at the same time. if the water starts to piss down right away down your exaust housing your upper water tube seal is gone, if it goes up the tube and barely comes out or has a hard time making it through you must have a block in the water passages somewhere... heres a vid to describe some of the techniques i just told you.

http://www.youtube.com/watch?v=gSWCV2mJz8Q