Mercury Thunderbolt 115

[Jkovalcik]

So I have a Mercury Thunderbolt 115. The motor ran great until I melted a piston. I replaced the Powerhead with a donor motor and kept the lower unit the same. Now I am unable to get water to come out of the Powerhead when running in water. When I use water muffs, water runs through without a problem, with the motor running. I've heard that the thermostat may be the problem but I'm unsure where it is located. Any other thoughts besides possibly damaging the impeller during the swap?

 

[Chris1956]

If that motor is an inline 6, it very likely doesn't have a thermostat. When you installed the powerhead, was the lower unit installed? Maybe the water pipe is not installed correctly or the driveshaft or powerhead splines are stripped. It is best to remove the lower unit and inspect the driveshaft splines and waterpipe.

 

[jimmbo]

I would replace the impeller. Which piston melted, and did you ever figure out why it melted? As to your wondering about a thermostat, It doesn't have one

 

[Jkovalcik]

I would replace the impeller. Which piston melted, and did you ever figure out why it melted? As to your wondering about a thermostat, It doesn't have one

I believe it was cylinder 4 if my memory serves me correctly. And it was more or less the improper mixture of oil and gas. Wasn't using a 50:1 ratio. Lesson ya learn the hard way

 

[Chris1956]

I would not think piston #4 would fail first due to an improper mixture. I would expect #1 or #3 to fail first due to overheat or clogged carbs. I would expect damage to all cylinders from improper mixture.

I recommend you clean all carbs, rebuild the fuel pump, link and synch the motor and make sure the waterpump is working, so as not to destroy another powerhead.

JMO...

 

[Jkovalcik]

Wel Ive already switched out he power head, cleaned the carbs and rebuilt the fuel pump and swapped the lower unit.

I guess what I'm really looking for is a step by step instruction to replace the water pump

 

[Chris1956]

A service manual is best, but here are the basics: Drop gearcase. Remove nuts and screw(if equipped) from water pump cover. Remove slinger and pump cover. Inspect SS liner for scratches. If scratched, replace it. Remove impeller and save drive key. Remove SS wear plate and two gaskets.

If in doubt about quality of driveshaft seal, replace water pump base and O ring. To do that clean driveshaft with sandpaper and solvent. Pry out waterpump base with large screwdrivers, Do not damage casting. Lubricate driveshaft and install new pump base with correct new oring and gasket. Grease base gasket and Oring.

Install new gasket to match base, then new wearplate, then new gasket to match pump cover. Now install impeller over drive key. It only fits one way.

Lube impeller with oil or soap. Place pump cover over impeller and turn driveshaft CW while pushing down on cover. After it seats, snug bolts and screw. If you had the base out, it may not be seated properly, so make sure it is inplace.

Lube driveshaft and shiftshaft splines, and install gearcase in neutraha