Tohatsu 3.5 2 stroke impeller change

[Kelpie]

After lying around in pieces for years, I finally put my old outboard back together today. It hadn't run in over ten years and started on the second pull.

I think the impeller has given up though, because after a brief test run when I got back to the boat and let it idle out of gear for a couple of minutes, I noticed steam rather than water coming out of the telltale. It had been pumping water well to start with.

The manual doesn't explain how to change the impeller, and the only YouTube video I found suggests that the impeller is behind the prop. I think that must apply only to the version without gearshift, otherwise you'd have no cooling in neutral.

So... how do I access the impeller on the great shift version of this engine?

 

[ChromeDome]

There's a difference between 3.5A and 3.5B models.

Part no. 3 in this diagram
8. 3.5B2 MODEL ONLY - GEAR CASE (DRIVE SHAFT) : , Reliable Source of Nissan Tohatsu Boat Marine Genuine OEM Parts

 

[yoda]

You need to split the leg jut above the two horizontal fins. First you remove the rubber bung in the side if the leg and unclamp the gear selector rod. Don't loose the clamp, can be a bit fiddly. after splitting the leg the bottom part pulls out and the cooling water pipe pulls out of its seal on top of the pump as you split it. All fairly obvious from there but can bit a bit fiddly getting the cooling pipe back in to the seal and the clamp back on the gear rod.

 

[jwilson]

"... a bit fiddly getting the cooling pipe back in to the seal and the clamp back on the gear rod." is correct. I would say "a bit fiddly" is an understatement, but it can be done eventually...

 

[WoodyP]

I have one of these. In Haynes manual terms a bit fiddly Haynes Manuals - The Real Meanings

 

[Kelpie]

Thanks all, I'm well versed in how this thing comes apart and goes together- yesterday it was reduced to gearbox/leg/head.
I had it in pieces to fit in an easyJet, and the gear shift lever was frozen. Will fit a new one but for now I've cobbled together a replacement from a bit of pipe. I'll need to replace the gasket for the leg/head joint too but I just wanted to see if it ran before spending any money.

So the impeller is going to be in the top of the gearbox? Not behind the prop as suggested in the video I found

 

[jwilson]

Thanks all, I'm well versed in how this thing comes apart and goes together- yesterday it was reduced to gearbox/leg/head.
I had it in pieces to fit in an easyJet, and the gear shift lever was frozen. Will fit a new one but for now I've cobbled together a replacement from a bit of pipe. I'll need to replace the gasket for the leg/head joint too but I just wanted to see if it ran before spending any money.

So the impeller is going to be in the top of the gearbox? Not behind the prop as suggested in the video I found

Yes

 

[andsarkit]

I had it in pieces to fit in an easyJet, and the gear shift lever was frozen. Will fit a new one but for now I've cobbled together a replacement from a bit of pipe.

The seized gear lever is a common problem as the plastic seems to absorb water and swell. If you can get it out in one piece it can be sanded down a little and well greased on re-assembly.
gear lever
This worked for me.

 

[Kelpie]

It did not come out in one piece despite my best efforts. £20 for a new one.

A bigger problem is that when I went to open up the water pump housing, I noticed one bolt already missing presumed sheered, and then I broke another one myself. Got the remaining two out over the course of half an hour using a lot of gentle heat, WD40, and patient wiggling.

The old impeller was intact but the bond between the inner and outer parts had failed, so the shaft could spin but the actual impeller stayed still. Will make it much easier to check I'm buying the correct replacement.

Now to get the two broken off bolts out... I guess I'll need easy-outs for that?

 

[penfold]

Left hand drills are a better bet, but easy outs can work with care.

 

[RunAgroundHard]

After lying around ... for years ...

Snap. Mine started first pull on fuel in the tank that was unknown age, immediately filled the garage with blue smoke. I added new Husqvarna XP Power 2 Pre-Mixed 2-Stroke fuel and the smoke went away.

Quick question, the coolant flow rate is more like a gravity flow rate rather than a strong jet of water. What should I expect?

 

[Kelpie]

Snap. Mine started first pull on fuel in the tank that was unknown age, immediately filled the garage with blue smoke. I added new Husqvarna XP Power 2 Pre-Mixed 2-Stroke fuel and the smoke went away.

Quick question, the coolant flow rate is more like a gravity flow rate rather than a strong jet of water. What should I expect?

I've had a few of these engines over the years, it is a bit of a dribble. If you can touch the underside of the powerhead without immediately burning your hand then I'm told it's all good.