2000 150 Optimax Lower unit removal advice

[Dougdawg]

I have never dropped the lower unit off this boat, so this is my first time.
1. There is a tube connector at the pivot point located at the base of the engine housing. How does this disconnect?
2. While the posted instructions from this website did not say to do so, I must presume I will need to remove the prop in order to not turn the drive shaft, right?
3. I have the the instructions from this website for rebuilding the water pump system including all the pictures. These rather stop at finishing up the water pump rebuild and I don't see any additional pages about putting things back together fluidly and not forgetting something important. Is there a post with additional instructions (with professional level tips) on reinstalling the lower unit, once I rebuild the water pump? My concern is getting that pitot tube back into the pivot cavity and reconnected and getting the driveshaft and shift shaft all line up properly at the same time. How do others handle that?

[tr20josh]

Not sure if you've found this thread yet, but it may have some helpful info for you: https://www.bbcboards.net/showthread.php?t=1086570

My Optimax 150 is a 2010 model, but I don't believe it's significantly different. I don't usually remove the prop when I drop my lower unit; it won't turn the drive shaft anyway unless you're in gear when you drop the LU. Actually I usually leave mine in neutral when removing, then put it in gear before I put it back on so I can use the prop to spin the drive shaft to get the splines to align. You'll have to turn the drive shaft anyway to get the impeller to fit into the housing.

To get everything back together, I first push the copper water tube into the adapter plate, then start running the drive shaft into the motor. First obstacle for me is usually getting the copper tube aligned with the plastic tube that sticks out of the water pump. Once I get those aligned, I can get the LU up to the drive shaft splines, which are usually not aligned. Holding the unit up at this point, I use a pair of needlenose to connect the pitot tube, then slowly turn the prop until the drive shaft splines are aligned. Then I back out the LU just enough to get the shift shaft splines aligned; can use my finger to align the female end through an opening in the motor just above where the LU attaches (can't find a good photo). I'm not a pro but hope some of this is helpful for you.

[EuropeanAM]

Good/helpful info above- hopefully your copper water tube stays in place.

Only exceptions I would make:

-Neutral position from start to finish (have someone turn flywheel to help align splines if needed)

-No GREASE on impeller (use Dawn Dish-Soap).

[SilverFox579]

When I wrote the tutorial didn't think it necessary to show every reassembly step since reinstall is simply reverse of removal.

Leave engine in neutral before disassembly, do not rotate driveshaft after removing lower, put a mark on the driveshaft and pump housing as shown in the tutorial and the lower unit will slide right in.

Same for water tube, if water tube comes out, reinstall it in the base plate before stabbing the lower unit, attempting to align it with base plate while holding lower unit is an exercise in frustration.

The pitot speed hose does not have to be reconnected to the legris fitting unless you're using pitot speed. I use Smartcraft and my pitot hose has been disconnected for several years. If concerned about debris getting in the legris fitting, cut off a short piece of the plastic tube, plug one end, and insert into legris fitting.

[Dougdawg]

Thank you for the reply!

[Dougdawg]

Well I rebuilt the waterpump. Impeller, housing, gaskets, Orings, everything was like new. The impeller had not even taken any permanent bends once free of the old housing. My concern is what to do next, since I didn't fix anything. What should I do now to fix heating up at idle? Thermostat? Sensor?

[JOE54]

recommend replacing thermostats and inspecting poppet valve for debris and movement ability , what is digital temp at idle and digital water pressure at idle

[SilverFox579]

recommend replacing thermostats and inspecting poppet valve for debris and movement ability , what is digital temp at idle and digital water pressure at idle

Important info!

[Dougdawg]

I only have a hose cup water supply connection. I have never let the engine run much just on the hose. I figure tstats are pretty standard replacement part. Does anyone know what the part number is for these and is there a picture or tutorial on the bbc board? I don't know what the poppet looks like or where it is located. I think I need a manual with pictures in it. Can I check temp on the head or a hose with an IR thermometer? How do you get digital water pressure reading?

[JOE54]

recommend OEM service manual for your engine , you can check temp on center of stat housing with IR you would need diagnostic tool for w/p , is your engine overheating or just doing maintenance ????? reinstallation can be tricky be very carful ..... good luck now JOE

[EuropeanAM]

Part numbers (and ordering) are available, by engine serial number on our website at: www.mercurypartsonline.net

When you add items to your cart, they automatically supersede to the latest number.

Thermostat replacement on the 2.5L Optimax is similar to the 3L... take a look at the post in the FAQ section on the 3L forum for somewhat detailed instruction.