Lower unit stuck on 18hp nissan

[acdc96]

I'm trying to change the water pump and the lower unt won't come off. I took the four nuts off and sprayed the unit with WD-40 and smacked it with a rubber mallet to try to get it free. Any ideas on how to get it off??? Is their any hidden bolts or it has to be in forward???

1988 Nissan 18Hp NS18C2

 

[pvanv]

Re: Lower unit stuck on 18hp nissan

I suppose you know that you must disconnect the shift linkage...

 

[acdc96]

Re: Lower unit stuck on 18hp nissan

Where would I disconnect that???

The lower unit hasn't even budged.

 

[pvanv]

Re: Lower unit stuck on 18hp nissan

You may have a stuck driveshaft. Either the splines were not greased the last time the LU was down, or maybe it has never been down, or the driveshaft could be twisted, if the motor hit an obstruction.

The technique to free the LU when the driveshaft is stuck is to use wedges and patience. Banging with a rubber mallet will only break parts off of the LU. As an alternative, you could pull the powerhead.

Locating things like the shift linkage is best done with the aid of the Factory service manual, available from any Tohatsu/Nissan dealer. Skip the aftermarket manuals.

The shift coupler is shown in the following diagram from the Factory parts catalog:

 

[Sea Rider]

Re: Lower unit stuck on 18hp nissan

The shift linkage is located way down lower tail. it's a tube in which both lower and upper rods are held together by 2 spring pins. Remove the upper one with a pin about same size or bit less than spring pin diam. Hope it's not stuck too. Better remove lower tail with small wedges untill it drops down, if removing powerhead off will probably need to changer lower pan gasket too as it usually breaks when PH is removed.

Happy Boating

 

[acdc96]

Re: Lower unit stuck on 18hp nissan

I'm gonna probably have to remove the power head cause their is no way to use wedges cause theirs no gap between the LU and the motor.

as for the gasket for the powerhead can I use a gasket maker? RTV engine gasket maker?

 

[Sea Rider]

Re: Lower unit stuck on 18hp nissan

Going back to your original thermo thread, if thermo's housing is a complete mess, imagine the condition of all internal water passages. Not even flushing your engine for a entire month in vinegar will manage to clean all water passages that way, must be mechanically removed. That is remove power head and all water related lids and by mechanically scrapping with a wooden sushi stick do a complete interior passages clean out if you want that engine to run as a champ besides cooling properly as when new. Will need a new therrmo, thermo gasket, head and lower pan gaskets for that job.

You must place a new head gasket with both mating surfaces immpecable clean for head gasket to sit evenly and well torqued to factory specs. Old gaskets are already hardened and compressed. If that's a 1988 engine you're looking at a 26 year oldie. If removing powerhead, must disconnect kill cord cables and throttle linkage to remove powerhead from pan.

Once done, remove 4 bolts that hols powerhead to pan base, grab powerhead with both hands one under carb, other under ignition coil and twist sideways while pulling powerhead up, repeat several times....good luck.

Happy Boating

 

[pvanv]

Re: Lower unit stuck on 18hp nissan

I'm gonna probably have to remove the power head cause their is no way to use wedges cause theirs no gap between the LU and the motor.

as for the gasket for the powerhead can I use a gasket maker? RTV engine gasket maker?

You can always start a slim wedge. Then go with thicker wedges, etc. Our mechanics do it all the time. It could take days of patience to pull a bad one.

If you are MacGyver in a 3rd world mud hut, RTV might get you by for a day. In the States, use real gaskets. No advantage to going to all that effort, and then doing a "barn job" when sourcing parts. At this point, if there is no cooling water flow at all, you will likely need to clean the passages manually, as Luis suggested, anyway, so you will need a head gasket, etc.

Again, always specify precise model/serial -- not the year of manufacture.

 

[TOHATSU GURU]

Re: Lower unit stuck on 18hp nissan

Are there any mud huts in Connecticut? I think they would be frozen mud huts this time of year. Of course, I could be wrong

 

[pvanv]

Re: Lower unit stuck on 18hp nissan

Are there any mud huts in Connecticut? I think they would be frozen mud huts this time of year. Of course, I could be wrong

They are expected to be snow-covered tomorrow and Thursday.

 

[acdc96]

Re: Lower unit stuck on 18hp nissan

Yep snow coming on Thursday... But no accumulation.
No the mud huts were replaced by houses many centuries ago.

Parts for this motor have been very hard to find and expensive. Not like my mercruiser where parts are everywhere.
I bought a water pump kit for my mercruiser for $18. I bought just an impeller for the nissan for $20.

 

[pvanv]

Re: Lower unit stuck on 18hp nissan

Any Tohatsu/Nissan dealer can source any still-available parts.

You do realize that the 18C2 dates back to the mid-1980's and earlier, right?
The 18C was superceded by the D and the E and now the 4-strokers.
Not many parts are available in the US for old 2-stroke cars, either.
I know that just getting a points/condenser kit for my Chevy Corvair is expensive...