Changing Impeller on 1994 70 hp Tohatsu

[wolf pup]

Hi all, new here.

I've been searching the net trying to find information on how to change my impeller. Boat owners I've talked to say it not that big of a job. I'm fairly comfortable around engine repairs but I don't have a clue where to start with this.

Don't have a repair manual and all my searches on the net here keep bringing me back to your site. I'm thinking this is a good place to ask.

Does anyone have a link to a good instructional video or repair manual for this engine. Or is it pretty generic. Sorry, not sure where to even start.

Thanks, Bob

 

[pvanv]

Re: Changing Impeller on 1994 70 hp Tohatsu

Start with a Factory service manual, to use as a guide. Don't do just the impeller; do the whole wp kit -- it will pump better, and the job will last longer. Same labor, so the increased cost of the kit is not very significant.

The wp service on these is the same as most all outboards: disconnect the shift linkage, drop the LU, and unbolt the upper wp housing. Make sure the drive key for the impeller gets installed with the new impeller. There are a couple of videos on the net showing wp service. The procedure is roughly the same for all OB's; the major differences are in the bolt patterns and the shift linkages.

 

[wolf pup]

Re: Changing Impeller on 1994 70 hp Tohatsu

Thank you Paul. Great information and gave me more of an idea what I should be searching for.

I think I've got a pretty good idea now from the two You Tube videos I watched. Is there any that you that you recommend? I was a bit worried about how all the linkage is connected but I think I've got it.

And I'll also take your recommendation about doing the entire wp. It makes sense.

One thing neither mentioned was what position the throttle should be in when I'm removing the lower unit. Forward, reverse?

 

[pvanv]

Re: Changing Impeller on 1994 70 hp Tohatsu

Not critical on the shifter location, as it is pinned, and will still be properly indexed when you reassemble. Often it's easiest to access the lower roll pin of the coupler in R.

 

[philipp10]

Re: Changing Impeller on 1994 70 hp Tohatsu

My two cents. The job is extremely easy. One hour max. As far as replacing the whole pump? I wouldn't waste my time. The other pump parts really do not wear so it won't make a difference if you replace more than the impeller or not. As far as lasting longer, no. Pumping better? No, besides the pump has more than enough capacity so that is really not an issue. I do have to ask though, where did you get the impeller. They are difficult or near impossible to find the original impellers. I do have a source for aftermarket, shoot me an email. philip.poeschl@tsi.com

 

[pvanv]

Re: Changing Impeller on 1994 70 hp Tohatsu

My two cents. The job is extremely easy. One hour max. As far as replacing the whole pump? I wouldn't waste my time. The other pump parts really do not wear so it won't make a difference if you replace more than the impeller or not. As far as lasting longer, no. Pumping better? No, besides the pump has more than enough capacity so that is really not an issue. I do have to ask though, where did you get the impeller. They are difficult or near impossible to find the original impellers. I do have a source for aftermarket, shoot me an email. philip.poeschl@tsi.com

Incorrect.
A first-timer may easily take a couple of hours.
There is a reason why the wear plate is called that. The kit includes the plate and cup, which improves side clearance, which does indeed make it both pump better, and last longer.
The Factory pump parts for the 70B are available from any Nissan/Tohatsu dealer, including me.

 

[philipp10]

Re: Changing Impeller on 1994 70 hp Tohatsu

Incorrect.
A first-timer may easily take a couple of hours.
There is a reason why the wear plate is called that. The kit includes the plate and cup, which improves side clearance, which does indeed make it both pump better, and last longer.
The Factory pump parts for the 70B are available from any Nissan/Tohatsu dealer, including me.

I have to respectfully disagree (at least somewhat). I did some measuring on the parts you state wear. They do but it is insignificant. These are stainless steel parts. The only thing that wears these are the sand that can be drawn in if you hit bottom. While you are technically right, the amount of extra pump capacity and pump life gained from changing these parts is negledgible.

 

[pvanv]

Re: Changing Impeller on 1994 70 hp Tohatsu

I have to respectfully disagree (at least somewhat). I did some measuring on the parts you state wear. They do but it is insignificant. These are stainless steel parts. The only thing that wears these are the sand that can be drawn in if you hit bottom. While you are technically right, the amount of extra pump capacity and pump life gained from changing these parts is negledgible.

The voice of experience tells me that even just tenths of thousandths of grooving in the side clearances makes a significant difference. They do in fact wear even without sand present. In the case of one of my DIY customers who is constantly running in silty water, he changes complete kits more than once a season. He doesn't do that because he likes to spend money on parts. Considering some shop labor rates at over $100 an hour, the increased cost of the complete kit is well worth it.

And yes, the kit for the 70B is still available. The kit for the 70A was discontinued long ago.

 

[philipp10]

Re: Changing Impeller on 1994 70 hp Tohatsu

The voice of experience tells me that even just tenths of thousandths of grooving in the side clearances makes a significant difference. They do in fact wear even without sand present. In the case of one of my DIY customers who is constantly running in silty water, he changes complete kits more than once a season. He doesn't do that because he likes to spend money on parts. Considering some shop labor rates at over $100 an hour, the increased cost of the complete kit is well worth it.

And yes, the kit for the 70B is still available. The kit for the 70A was discontinued long ago.

How can you possibly know that the pump is moving more water with a new cup and wear plate than without. Unless you have these parts in a lab and are measuring flow vs pressure output, you can't. I'll agree, any grooving probably results in loss of pumping capacity however, like I said, these pumps are so over-sized that for all practical purposes it really does not matter.

 

[emoney]

Re: Changing Impeller on 1994 70 hp Tohatsu

I think it's safe to say that some folks like to change the plate and thus the parts suppliers provide a "kit". Others feel comfortable changing the impeller alone and again, there's an option for that. Outside of that, most everything else is supposition so why argue it?

Especially since the OP hasn't been in this conversation for a couple of months, lol.

 

[philipp10]

Re: Changing Impeller on 1994 70 hp Tohatsu

How can you possibly know that the pump is moving more water with a new cup and wear plate than without. Unless you have these parts in a lab and are measuring flow vs pressure output, you can't. I'll agree, any grooving probably results in loss of pumping capacity however, like I said, these pumps are so over-sized that for all practical purposes it really does not matter.

I should clarify, the reason I know the pump is well over-sized is, my motor started over-heating this summer, but only at idle. I took apart the pump. I was running on just 3 of the 6 impeller blades and other than at idle, it was still cooling just fine. Take care.