Thread: 2 Stroke Mercury 40 Water Pump Replacement

Pulling the Lower Units on different engines are mostly the same untill you get to the shift design. Old Evenrude Cross Flow's you had to remove a pin below the carbs which was way easier to do with the Carbs off. Little engines like this a Jamb Nut Connection is unthreaded to release the Shift Shaft from the Lower Unit Shift Rod.



You almost always have to remove the Skeg to access Lower Unit bolts under it. This engine has a Stud which was caked in corrosion. I pack the bolts with Quicksilver Extreme Grease on the reinstall. I cleaned all the gunk off first.



Then the remaining bolts are removed from each side of the Lower Unit. Once removed grasp the Lower Unit firmly and give it a wiggle it should release. Clean all the Alignment pins before reinstalling. V-6 Lower Units can be quite heavy so remove those with someone standing by if you can.



The tube that carried the water up into the Engine Block is almost always around 5/8in in Diameter. This is where I hook up my circulation Pump to chemically clean out a plugged Engine Block.



The driveshaft Splines are always greased with Extreme Pressure grease but you never put any grease on top of the shaft as it will not compress. Fill the Splines on the side only.



I took close up pictures so you can see where the grease is and where it is not.

This Quicksilver 2-4-C is the grease I use on the Water Pump Output Seal. A thin coat is all that's needed to prevent the Water Tube from snagging.

You knew that I’m about to have to do this on my 25 tiller Merc. Most of my experience is on older OMC stuff or my ‘88 150 mariner. While most of what you tell of is somewhat normal, a few things look to be different. Shop quoted me $175 labor plus party’s to do this so I will be entering yet another learning curve. Still pumping good as of now but this impeller has been in since the middle of ‘22 so I’m trying to stay ahead of things a bit.

I bought this boat in ‘09 and didn’t change impeller for too long cuz it was still pumping water and gave no signs of overheat. Turns out I got to it just in time cuz the rubber was beginning to come off in small pieces and could’ve blocked water jackets and made a much larger mess.

And just to make it easier to work on I grabbed my saw ponies and a couple of one by stuff and never had an issue. And I second the statement that v6 lower units are stout and awkward to handle. Think ahead cuz ya don’t want to drop these things. This impeller was changed on 2/19/2019. Ten years is way beyond life expectancy and I truly dodged a bullet by getting this one changed before it went catastrophic. I usually drove too fast and an overheat at high rpm’s wouldn’t have been good. Thanks for the play by play John, kinda like my old Chilton’s manual. Thorough.

Originally Posted by Rojo

Pulling the Lower Units on different engines are mostly the same untill you get to the shift design. Old Evenrude Cross Flow's you had to remove a pin below the carbs which was way easier to do with the Carbs off. Little engines like this a Jamb Nut Connection is unthreaded to release the Shift Shaft from the Lower Unit Shift Rod.

The last time that I changed the impeller on my XP150 with carbs required both of my kids and me to strategically get the shift shaft and linkages lined up properly--one kid at the shifter and one kid pushing the linkage into alignment so that I fasten it up.

Skeet, you were close to the Edge as they say. I really hate when I pop a water pump impeller cover off and see the impeller in pieces. My procedure is the same when that happens, pull all the covers & thermostats and hook a impeller type water pump to the output tube to the block. You have to flush the pieces out reassembling the impeller so you know for sure you got every piece out. I've had to pick them out of the water jackets before because the impeller still had enough pressure to open the By-Pass Valve allowing pieces to enter the water jackets.

jjue1979, the newer engines Shift linkage just spline together for the most part but if you're like me you may never own one. The engine you have is one of the most reliable V-6 engines OMC built. You know I have one stashed under a blanket in my shop. A little tweaking to the Port Timing, Blending of the Block, Re-Jetting the Carbs, and Shaving the Heads (Squish must be corrected also) and your engine walks right over the 225HP mark.

Got up this morning and filled the Gear Case with fresh Full Synthetic Gear Oil. I had it draining over night due to the low temps here. You have to tilt them up so your lower drain screw is at the lowest point to fully drain but the prop end of the gearcase must be the lowest when you fill. This ensures no air is trapped in the gearcase giving a false full.



When I looked under the Carb and saw Dirt Dauber Nest material inside the Engine case I had to clean it out. It was in a bad spot and looked like it was tracking to the Carb so I pulled it off to give me more room to clean.



Removing the Carb left a big hole in the Engine and a open fuel line so I put Duct Tape over the old Carb gasket and a micro Zip-Loc bag over the Fuel line securing it with a Rubberband.



I discovered a Degreaser that IMHO has no equal. Sam's Club sells this stuff, it's Members Mark Brand, comes in gallon jugs. It will remove every bit of crud in a Bilge. I use the spray bottle for application as some of the bilges are huge so nasty areas I can't reach I wet down with this Degreaser and just wait. I stream of water 15-30 minutes later and the area rinses clean. Well when cleaning out the Lower Cowling of a Outboard I use it first then after 30 minutes follow up with Gunk Foamy Engine Cleaner. The Double Wammy does the job.



Don't use a hose nozzle set to stream always set it to Shower when washing out a Cowling. If it doesn't come clean the first time let it fully dry before repeating for the best results.



With all the contamination washed out I used compressed air to finish drying the water out of tight places.



The Carb was Funky so I took it apart for a solid cleaning. Once complete, passages open, and new float & needle installed I put it back together.



That's the original float from 1999, I can't say about the needle but I installed new, hopefully it will last over 25 years.



I installed the Carb but the Fuel line was not cooperating. I'm ordering the molded hose to replace the hose seen here but I need this rig going. This little Tin Boat is as Deadly as Thor's Hammer in wintertime so the fuel line must go on.



Enter the humble Hose Pliers. I've got to say what a cheat to get that fuel line back on the barb.



Now that the line is on and secured I can install the Air Baffle.



I went ahead and replaced the Fuel Filter Screen too. When re-installing the Fuel Filter Bowl a drop of 2 Stroke Oil or engine oil is needed on the o-ring seal at the top of the bowl.