73 25 HP lower unit problems.

[matridium]

I just bought a boat of a man for 800.00 with a johnson 25HP 1973 motor. It started right up and seemed to run very well. I feel was a good buy. However now that I have had a chance to really look at the motor I have noticed some things that are not right. I changed the lower units lub and it came out looking like heavy wipping cream, off white.. I know this means there was water in the lower unit. also when I ran the motor I noticed there was no tell tail. Is there a tell tail on this motor? also I know I am going to want to change the water pump. I am prepared to do the work. I have the Clymer manual already. However I was taking the lower unit off today and notice when I was getting ready to disconect the shift rod that it is very baddy rusted. Is this an easy part to get? Also is it wise to use an RTV sealent when puting the lower unit back on as too keep out the water. I noticed that one of the 5 mounting bolts was missing so this could be a way for the water to get in. Also does this motor have a thermostat? I can't find it. <br /><br />thank you in advance<br /><br />Michael Moore

 

[rabidfish]

Re: 73 25 HP lower unit problems.

I try to help...<br />Refill the lower unit if you are not ready to look at it immediately. If you are, the remove the lower unit and pressure test it to find the leak.(probably the shift rod seal, or under the water pump) Once you know where the leak is, you can be certain that you have fixed it. Anyways, reseal the entire lower unit anyway. You can put your water pump on now also. You do not need RTV. That part of the housing has water from the cooling system in it anyway.<br /><br />There is no "telltale" on that engine. You should see a fair amount of water mixed with the exhaust at the rear, underneath the powerhead.<br /><br />Do try to get a bolt for the missing one. Do not use a steel bolt from the hardware store. Get a proper bolt(stainless steel) preferably even one from a used engine, or order a new one.<br /><br />The thermostat is located under the "triangle" shaped plate on top of the cylinder head.

 

[matridium]

Re: 73 25 HP lower unit problems.

thank you <br /><br />I found the thermostat late last night by just looking at the power head the thermostat is in bad shape it was rusted open!! I assume this will impare the engine before it warms up. also I will be able to work on the lower unit but I want to know how do you pressur test. I have an air compressor and a vacuum pump, which is the best to use. <br />Also is the shift rod an easy item to get becuase it is really rusty. <br /><br />Michael Moore

 

[rabidfish]

Re: 73 25 HP lower unit problems.

Use a hand pump to pressure test. You'll hold a maximum of 15psi for 10 minutes.