Merc 115 thunderbolt

[racerone]

I do not believe your motor has an overheat warning horn.---Or a " shut it down I am not happy switch " for overheating.-----Those motors require a new impeller every 2 or 3 years !!----Install a new one now.

 

[Itz gnome]

Are all Merc impellers the same? Does anyone have a pn?

 

[Chris1956]

Not all Mercs share impellers, however, there are only a few. Look for one for an inline 4 or 6 cylinder Merc. Replace the impeller, stainless wearplate and two gaskets, one on each side of the wearplate.

They are widely avail from Sierra, GLM, OEM and others.

 

[racerone]

The part # for those went something like this 47- xxx84 and was common from say 1964 to late 1980's on the 4 cylinder / 6 cylinder inline outboards / V-6 outboards and many stern drives too.-----Every boat shop should have a couple in stock !!!

 

[Itz gnome]

Replaced impeller today. No water still from spitter.

 

[racerone]

Testing in a bucket or on a hose ?-----In a bucket water must be 6 or 8" above the impeller.-----Perhaps tell tale is plugged.

 

[Itz gnome]

Got a set of mugs on it. I can feel air pressure through tell tale. I’ve noticed in a lot of videos that water comes out in the vent holes above the water intake vents. I have nothing there either.

 

[Itz gnome]

I pushed a wire nearly 1 foot into tell tale and tried again. Still no water. Do I try taking lower unit off again? Checking what? Somewhere else to look? I was not able to remove the water tube from mid section prior to re-installing lower unit.

 

[Itz gnome]

Tried in a bucket as well with same result. Could it be the supply tube not seating correctly?

 

[Itz gnome]

I feel as though these two tubes are not locking together. They slide inside very easy but nothing to seal them together. Am I missing something?

 

[Itz gnome]

Tried hooking up hose straight to intake pipe( lower unit off) started motor and had water come out by spark plugs with motor running??? Looks like cylinder 3&4 any thoughts?

 

[racerone]

Do some measurements to make sure tube is reaching and sealing in the pump housing.

 

[Itz gnome]

Measurements say it should hit by about half inch. However shouldn’t I be able to remove the upper pipe? It seems all my water isn’t flowing to motor? Possibly a crack in the pipe?

 

[racerone]

Water leaking around the sparkplugs means that the water jacket cover gasket is leaking.

 

[Itz gnome]

How difficult is that to replace?

 

[racerone]

On a fresh water motor it is just a bunch of small bolts.----Nothing technical to it.

 

[Chris1956]

OK, a couple of things.... The impeller had a stainless steel drive key to lock it to the driveshaft. It fits on a flat part of the driveshaft. You did install it, right?

Grease the shift and driveshaft splines. Make sure motor and control are in neutral.

The white plastic pipe sticking out of the waterpump is a guide to make sure the copper waterpipe fits into the waterpump.

When you install the gearcase, use fingers to stick the copper pipe inside the white plastic tube. Now wiggle gearcase until driveshaft hits end of crankshaft. Turn flywheel until they mate. Now mate the shiftshafts. You may need to rock control a bit to make it happen.

Use only fingers to tighten nuts until you are sure driveshaft is mated, then you can use wrench.

As for leak near spark plugs. Older motors usually have stubborn bolts. Breaking them is a real possibility. It is a real PIA to drill the broken bolts out and retap them.

Dry out the area of leaks and put some silicone on them to seal leaks, is my opinion.

 

[racerone]

The lower unit should slide right in place.---Not a good idea to use the nuts to " force " it together.

 

[Itz gnome]

Lower unit mates back up real nicely. No problems lining everything up and yes I did install key. Definitely pumping water it just seems like midshaft if filling up more than anything else. Drive shaft was wet when I removed lower unit second time. I’ll be checking into ordering water jacket gasket on Monday when store opens. Would silicone stand up to the pressure? And or heat?

 

[racerone]

There is not much pressure and not much heat there.-------Do not use silicone on outboard motor gaskets !!-----