1973 Mercury 50 HP Thunderbolt No Pea Stream

[michael0972]

8)
I just purchased an old pontoon that I am planning on using to scuba dive off of. I bought it from a private individual and when we took it out for a spin I noticed there was not water comming out the pea streem. I asked the guy about it and he said it worked the last time he had it on the water 3 years ago. The boat did not seem to get hot while we ran it, so I bought it.

I replaced the water pump today and took it to the lake to test it out. There is still no water at the pea stream. I ran a piece of wire up the hole as far as it would go, which was probably 18 inches, it did not seem to be plugged at all. I took it out about 100 yeards from the dock thinking that I needed to rev the motor up a bit more to see if more pressure would force it out. I then noticed smoke or steam starting comming out for the pea stream whole, but no water. The motor then reved down on its own and then quit. We drifted to shore and I wenched it on the trailer.

Any ideas what is going on? Did I overheat it and blow up my motor? The motor was very hot when it quit. But it probably only ran for a total of 5 minutes.

 

[Plainsman]

Re: 1973 Mercury 50 HP Thunderbolt No Pea Stream

Welcome to iboats!

I am no expert, but if it was very hot, probablly not a good sign.
What is the serial # of the motor and hp?

Might want to look at this as well:

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=36;gtid=1035575

Also get a pair of muffs so you can run it off the hose to test it before you go on the water.

 

[tmcalavy]

Re: 1973 Mercury 50 HP Thunderbolt No Pea Stream

Those are great motors. I had a 74-75 model...wish I still had it but it went with the old boat at sale time. Pull the faceplate and cowls off while the boat/motor is in the water. The side covers on either side of the cylinders are the water jackets. Pull the lower unit and check to see if the impeller is still keyed to the driveshaft...while you're doing this check the driveshaft for pitting. Check the tube that carries water from the pump up to the head. Also pull and check the tell-tale (pee) hose from the cowl outlet back to the head. It should pee a good stream above 1200 rpm, but like my old Merc it will taper off below that speed. It should be making water at idle and at speed. You may have an obstruction somewhere between the pump and the head and tell-tale outlet. You can tell if its running hot if you cannot touch those sidecovers when you get it started and running...when it's cooling properly they will be cool to the touch. No thermostat in your outboard so that's not the problem. Take it one step at a time logically and you'll find and fix it. That one time of running it hot probably didn't hurt anything, but a compression test will tell you for sure. Each jug should have over 100 compression and all four should be within 5-10 percent of that or better. If the driveshaft is pitted (pretty common) it will affect the cooling...I had to pull mine and have my Merc guy send it out to be built up and then turned back down, cost about $75. That's a workhorse outboard...get a factory service manual and you can do most of the service/maintenance yourself. Post back with what you find.

 

[michael0972]

Re: 1973 Mercury 50 HP Thunderbolt No Pea Stream

Thanks for the info. You were correct. The key was missing. It was not there when I replaced the impeller, so I did not even know that there should have been one there. I was wondrering why there was a grove in the impeller. That would explain why it did not work before. I am going to the boat shop tomorrow to get one.

Thank you very much for the help Master Chief.