Mercury 500 - Clicking instead of starting, loses power when warm

[p38fln]

I have an ancient Merc 500 engine with a boat I got on Craigslist that I finally got to try out the other day. I charged the battery with a smart charger for a week, and all I got was clicking when I tried to start it. Since I was waiting for the boat ramp to clear after this, I kept turning the key to start and all I got was more clicking. I tried gently tapping the side of the starter with a screwdriver handle while someone turned the key to start, but no luck. Then I tried the rope on the flywheel, and the 45 year old rope shattered into powder.

After the couple pulling their boat out finished screaming at each other and pulled away, I tried clicking the key to start one more time and the starter actually engaged! I had already primed the fuel bulb and set the warmup/high idle lever. Choke button is missing.

It cranked for about 15 seconds, and then started. No clicking, and it cranked at a pretty decent speed. At idle I noticed water running from the upper unit, a trickle like you would get from a fridge water dispenser, not sure if that's normal or not. It wasn't running from the back, just around the sides.

So I drove it around the lake a few times (Staying as close to shore as the law allows) and gave it full throttle a few times. It seemed to go as fast as a 50 HP motor should go, with the boat almost onto its pad but not quite.

After it warmed up, it didn't want to go as fast - still fast enough to throw a wake, but not enough to lift the boat. I let it idle for about 15 minutes, and it had all of the power back again.

Eventually I stopped playing with it and when I put it back at idle speed, it shuddered a few times and stopped, and no amount of fiddling with the key would make the starter engage again. So I paddled it back to the boat ramp and called it a day.

So any ideas on what I need to do to this thing to make it run somewhat normally?

I'm thinking at a minimum it needs new plugs and a starter

 

[racerone]

I would never spend money on a new starter without confiming the old one is bad.-----Could be a simple wiring issue.-------Clean carburetors are a must.--Plugged carburetors can lead to serious engine damage.

 

[GA_Boater]

I'm with racer on this about the starter and cleaning/rebuilding the carbs.

How old is the battery? Take it to an auto parts store and have it tested. Clean all the battery connections, both power and ground, from the battery to the starter, including the solenoid - Bright and shiny!

The leaking water needs to looked at. Take the cowling and covers off to see where it leaking.

You might as well invest in an impeller or water pump kit, too. Cheap insurance for the motor to reach it's 46th birthday.

 

[CharlieB]

Ditto cleaning the battery cables, BOTH ends, and the starter cable. Charge the battery then take it in for a real load test. If it still won't crank grab your trusty jumper cables. connect the ground from battery to the motor block. Connect the Pos to the battery then strike it directly to the starter lug, if it tuens now that proves a poor connection. Either the relay or a battery cable corroded past the terminals and under the insulation.

Clean the carbs and REBUILD the fuel pump. Often a weak fuel pump is misdiagnosed as a carb problem when it is simply running low on fuel. Initial acceleration can be fine but shortly after just sort of runs low on power. That is a weak fuel supply and most dangerous to the motor as the upper carbs cannot stay full of fuel, get low, run lean, and melt the upper pistons! Rebuild that fuel pump!