Impeller maintenance

[rfrance0718]

I have 2 Tohatsu 6hp 4 stroke engines. One of them I ruined several different ways. (not before I got 14 great years from her) First thing I did was to avoid the impeller maintenance, thinking that it would be difficult) Next problem was that it fell off of its stand when I was doing a gear lube change. That cracked the bowl, but it still ran fine, but the cover wouldn't fit. Finally, I tried to do the impeller maintenance and found that the drive shaft was terminally stuck in the power head. When I finally got it to come free, it actually pulled the shaft out of the lower unit. The shaft is still stuck in the power head, but if I ever got it free, it might all go back together.

My second Tohatsu (actually Nissan by brand, but exact same engine) was given to me. It has run well, albeit a little fast in idle, but I had no idea if its impeller had ever been changed. So here I go again. I went about following the instructions (you tube) for pulling the lower unit and, halleluiah, it came right apart. I bought the pump kit with all of the gaskets. The top one looked bad and I was sure that the others were similar. That's when I ran into the first issue. The gaskets were seemingly permanently attached to the base of the pump. This problem I managed to solve with a can of gasket dissolving foam and 2 days of wire brush. (some pundits said that the wire brush was a no-no, but others said that it was the only way, and that it all worked in the end. At that point I reassembled the pump around the drive shaft and was ready for reassembly, which is my new sticking point.

Several videos showed the demonstrator struggling with this, so I'm not surprised. The one guy, finally found success by standing the motor on its head so that gravity became a partner. So that's where I am now. Motor upside down (oil drained first), and drive shaft splines still not interested in nestling into the socket. Good thing I'm not in a hurry, but I would like to figure it out at some point. It seems like hundreds of attemptsYou cannot view this attachment.You cannot view this attachment. at every possible angle would find success, but maybe I'm only at one hundred, and haven't yet paid the dues in full.

The second picture shows the view where the drive shaft belongs. The hole in the diamond shaped plate is easy, since you can see everything up to that point. After that you are working blind because the lower unit has dropped down enough to block any view. I always get a hard clunk, when I'm several inches from home. Sometimes a softer feel, where maybe it's at the opening but won't go down. I've tried rotating the prop and the flywheel to see if the splines aren't matching up, but no sense of success at all.

I always wake up with a fresh idea, and I'm getting ready to try today's concept. Does anyone have some magic dust they can send?

[Wolverine]

Sorry I can't help. I'm the worlds worst mechanic. I bought a 4hp Tohatsu in December 2009 and put it to work in January 2010. In was in the shop twice in 4 weeks. It would only run with the choke on. I put it away and pulled out a 1985 Nissan 5hp and it's run without a problem since. In 2018 I had a new carburetor and impeller installed in the Tohatsu for a trip to the North channel. It ran great until that year and hasn't started since. It now keeps my 1966 Chrysler 3.5hp company in a corner of the garage.

I will need to thank for reminding me to have it fixed so I can sell or trade it for a short shaft.

Good luck!

[Riley Smith]

First, before going ANY further, make sure the socket in the head is not reamed out. Can't see from the picture. Take your time and get it in focus and visually inspect. Then get it CLEAN. Gun cleaning kit does a good job. Then install the foot and turn the shaft to get it all aligned by turning the prop. You have to do the shift rod at the same time too, and all this is mostly done by "feel", but fiddle with it a bit and you'll KNOW when it is there. Any burr must be dealt with, the shafts CLEAN, and lightly lubed. 10W-30 is ALWAYS laying around. THEN you can tap the foot downward to get the shafts to engage fully. NO...not SMASH the foot down, tap. Maybe so much as a rap if it starts to go. I LOVE a dead blow hammer. At least that's how I think I'd proceed.

[Frank B.]

Agree with Riley, have done my Nissan 6 hp sail pro a couple of times and it seems it is just by feel.  Often it does not go up initially, stops an inch or so and than twisting back and forth or rotating the shaft will cause it to eventually drop in.

One thing I learned about those pumps when I almost replaced the impeller because I wasn't getting any cooling water when I tested it in a barrel is that you can't just have the water level above the intake, it has to be at the level of the pump.  If it is not, it won't prime and you might think, as I did, the impeller is bad.

[rfrance0718]

I went to the hw store and bought a dowel rod that was a bit slimmer than the shaft. My idea was to see if I could get it to go into the socket with the help of a visual line of sight. I thought that this might help me get and idea about the appropriate path. I was successful at this, so then tried the actual shaft again, w/o luck. Now I'm trying to reproduce what I did with the dowel, and I can't get it to go in! Giving up for the evening.

[Doug SC]

I have the 5hp Nissan and have change the impeller 3 times in the last 9 years. I know of what you speak but seem to be able to line it up. I try not to rotate shaft when I take it apart. Where I have a problem is with the link to the shift rod so I can get it to go from R to N to F it has to be in just the right place on the shift rod. I think Riley's advice is on the money. Oh, I never turned the motor upside down. and the first time took the longest to get it right. Good luck.

I had to change the impeller the first time because I pulled the boat out with the motor in idle. Duh! the second time I hadn't put the motor mount down, so the prop was out of the water when I started the motor. Double DUH!! both times were within the first 2 years I owned the motor. It was because I so rarely used the motor anyway. That's my story. Believe me I am very aware of not doing this now. The third time was to replace it before it failed from wear.

[rfrance0718]

Thanks for all of your ideas. I'll try to put them in play abd see what happens. Fingers crossed.

[Riley Smith]

Spray it down with some PB Blaster or WD=40 too! If either drive has balls like a ratchet extension, make sure they're as free as possible.

[rfrance0718]

Got it!  What a relief. The biggest problem that I was having was not knowing if I was even close. So I pulled out an old 12 v light fixture, disassembled it, and used the socket, wire, and the bulb to drop it down into the tube, so that I could really see the socket. Then I went back to my dowel rod and I could see that it was hitting home. Next I followed  Riley's advice and made a gun cleaner with a coat hanger and found a tubular brush to clean up the socket best possible. I also cleaned up the splines on the drive shaft. Finally, leaving the little light dangling half way down the tube I lowered the unit down, using my visual to get pointed in the right direction, and lowered it until it stooped, not quite in. Next I pulled out the light, wiggled a bit, turned the fly wheel a bit, and felt a bit of give. At that point I pressed it on down. Wow!

I had forgotten about the gear shift rod but it had found its path, and it felt like the tubes mated as well. Last problem was to mate up the gear rods. One you-tuber had suggested totally removing the clamp, which I had done. It was a little tricky for may fat fingers, but a pair of needle nose, and a 10mm closed wrench allowed just enough room. The gears do shift and prop turns the flywheel in forward and reverse, leaving no resistance in neutral. Last things are to fill oil reservoir and replace the lower unit grease. Then a test. It's 24 degrees out and dealing with a hose and trash can full of water doesn't
sound wonderful. I've got other stuff to do until weather warms up next week.

Thanks again for your stories. Kind of knowing you guys made a difference in how much I trusted what you were saying. I'm pulling the Oday down to Florida in a week.

[rfrance0718]

And finally. New oil and gear lube, shift rod grommet back in place. A little linkage tweak when it didn't want to start , and guess what? It works. I can go on my trip now!You cannot view this attachment.