1992 - 2002 Tohatsu/Nissan 25 Cylinder Boring Question

[LukeFishWalker]

Once I get the opportunity to spend at least half a day outside without melting or
floating away with the heat and rain, I will pull the powerhead off the OB and remove
the rest of the bolts from the exhaust cover. There's no point in removing all the
bolts while it's still on the driveshaft housing because I cannot repair the broken
bolts while it's attached. I guess I could with a right angle drill....Something I
do not have. When I get the cover off....I will defiantly take pictures before cleaning
and post them to the thread.

Thanks For Your Time And Patience,
Lukus

 

[Sea Rider]

Do you plan removing powerhead off pan, it's just one base gasket more, much bolt friendly to work with.

Happy Boating

 

[LukeFishWalker]

I have plans to remove the splash pan and break the 8 bolts that go through the drive shaft housing
that thread into the cylinder housing. And replace gasket 3C8013034M when the assembly is repaired.
I ordered a STD 6 ring set and I picked up a hone so that when I get all the parts, I can do it all in 1 day.
Thanks For Your Time And Patience,
Lukus [h=1][/h]

 

[LukeFishWalker]

No Title

Update:
I found the time to take the powerhead off and I found how water has entered the lower
piston crankcase on the Tohatsu M40D. The lower seal is destroyed and it appears that
corrosion and rust has taken over.

 

[LukeFishWalker]

No Title

Here's 2 more pictures.
The exhaust plates were sealed perfectly.
I spoke to a mechanic that explained to me that the moisture likely entered the
lower crankcase by way of the lower oil seal and the drive shaft seal being damaged.
He explained that the water is allowed into the lower crankcase by way of the exhaust
in the mid section unit if the engine was mounted very deep/low on the transom.
Which, there is in fact a water line well above the cavitation plate.

 

[LukeFishWalker]

No Title

I'm trying to figure out how I keep getting the screws put to me?
I've abandoned this OB and cutting my losses,
it's going to a OB Boneyard for WHATEVER I can get for it!!

 

[Sea Rider]

Gee, you have opened up a Pandora Box, not an issue replacing gaskets, seals, but dealing with new oversized pistons, boring cylinders, labor costs adds more money. Personally love rebuilding powerheads at 1/4 the cost of a new OB.

Happy Boating

 

[LukeFishWalker]

If I owned a shop that afforded me the opportunity to bore,
I would certainly do that. But, I already have a project that
involves machinist work (The Tohatsu M25C2) that needs
boring. That engine stands a much better chance of success
mostly because of the fact the crankcase came from Ohio
and has never seen any salt water. Where as, this M40D
has seen more than it's fair share of salt water and the water
jackets show the evidence. There's more than 1 spot that
the casting is 1/8" or less to the cast sleeve.
Therefore, I am not going to spend $1000.00 on a block
that has this much saltwater damage. If it were just a
re-ring....I could justify the $200-$300.

NOW, which 40 is the better of the 2 models?
M40D or the M40C
I have an opportunity to get a Nissan NS40C for $750.00.
This one is still running and I know the guy much better
than the fool I got the M40D from.
Thank You For Your Time And PAtience,
Lukus

 

[pvanv]

The C has better throttle response, because of less moving mass. The D has better parts availability.

 

[Sea Rider]

Lukus,

M40C is a 2 stroke OB, M40D/M40D2 is a 3 cylinder OB. Both are different OB's. 40C is bulletproof, has been discontinued recently, should have lot's of spare parts availability. If knowing owner has taken good care, for $ 750.00 go for it...

if you been boating with a 3 cylinder 40 HP and plan passsing to a 2 cylinder 25/30 HP probably won't like its performance, better pass to a 2 cylinder 40C. It's right in the middle of both mentioned HP models.

Happy Boating

 

[LukeFishWalker]

Update:
I was able to get $400.00 for the damaged M40D at a local shop known for dealing in used parts.
I went back to craigslist and found a really nice guy in LaPorte, TX with a 2002 M40D2 3C8 that was
in his garage. I called him Sunday morning (The Post Was 3 Hours Old) and he said a man
was going to his house Monday morning to buy it. The wife & I packed a few clothes and hauled
butt to LaPorte and beat the other buyer to the punch. By 3:30pm Sunday I had the Tohatsu M40
in the back of my Tacoma for $1350.00. The owner explained to me that he only used the motor
on a 20' AllWeld flat boat during duck season. And he hunted maybe 15 times a year.
And the engine is spotless, the engine runs fine and I am happy as a camper.
He threw in two 6.6 gallon tanks with bulb and Tohatsu fitting, 2 deep cycle batteries, 2 props
and a Tohatsu tach. The props showed signs of oyster shell damage. I have a brand new 14P M40 prop.

Then, we spent the night at my brother's house in Baytown.

Thank You For Your Time And Patience,
Lukus

 

[Sea Rider]

Congrats, nice purchase with out of this world price for the whole package..

Happy Boating

 

[LukeFishWalker]

Sea Rider,
I was doing an internal water jacket cleaning with 1 to 1 vinegar.
I used about 6 gallons of vinegar, then filled the empty containers
to displace water in order to raise the water level.
I noticed the cylinder head near the thermostat was "Warm".
Not hot to the point where I could not leave my hand on it.
My son works in the water treatment field and he brought his tester.
The Ph is 2.8 and the water temperature got up to around 135F and stayed there.
I would guess there was close to 8 - 9 gallons of usable liquid that the
water pump could utilize. The water inside the plastic drum was warm
and we let it run for at least 45 minutes. The temp never got above
the 135F - 140F.
In your professional opinion:
Is 135F - 140F acceptable when operating in a closed system like the drum?

Thank You For Your Time And Patience,
Lukus

 

[Sea Rider]

Lukus,

Wow, do you happen to be a shareholder of the Heinz Company LOL!! 6 gallons of vinegar would be consumed throughout my entire life on salads. Some issues :

Tohatsu doesn't recommend flushing an OB for long term periods on barrels, too much oily water around and impeller sucking it in and peeing it out that could adhere inside water cooling system and degrade it's ability to properly cool the OB.

Temperature on tank/barrel must not exceed 25C?/77F? as you don't want to cool OB with hot water. If extremey hot with prolonged usage could experinence an unwanted OB overheat/seizure.

Try Salt Away, probably cheaper than buyig huge gallons of vinegar if plan removing more salt layers, small obstructions in a near future. In reality the only possible way to remove near 100% of salt layers, crusts reamains on used OB's is mechanically, that's if OB is used on salt waters, flushed after use, much worse if owner doesn?t believe that's is a must flush OB with fresh water after use. Second hand OB's could turn into Real Pando Surprise Boxes...

Happy Boating

 

[LukeFishWalker]

I had gone to the Dollar Store and purchased the store brand vinegar.
Each gallon was $2.70. Heinz is a little bit too proud of their product.

I pulled the thermostat and the jacket was near spotless.
I checked the impeller and it appears that it's been changed lately,
just like the thermostat.....They both look brand new.
Which makes me wonder if this dang thing had a previous heat issue.

As far as the "Prolonged" exposure to water above the 77F....
As I think back - 45 minutes may be exaggerated a little bit.
The water inside the drum was probably close to 77F after
it ran for 20 minutes.

Here's the strange thing....
I put the ears on and flushed the system for 10 minutes and even with
the cooler water from the hose, the cylinder head still got as warm
as it did in the barrel. And the temp of the water out the tattle tail was
right at 140F. If I idled it up to 1600rpm, the head seems to cool off a bit.
Meaning, I could leave my hand on it for as long as it was at a higher idle.

So, the next step is to drop it in the water once I get a little bit bigger
transom saver. The weight difference between the M25C2 and M40D2 is
quite a difference for my old wore out saver.

Thank You For Your Time And Patience,
Lukus

 

[Sea Rider]

Lukus,

If ear muffs doesn't seal 100% against lower leg intake ports, having less water along pressure going up head will definitely produce a warmer cylinder head, Water pump sucks more water from a barrel that it does from ear muffs. If thermo and impeller are brand new, don't worry too much about OB temp.

What you should do, go for a run for some minutes, gear neutral, go to transom and put your hand right under idle relief port if having one, if can feel medium cold and warm intervals thermo is working as expected. Not an issue if previous owner has changed parts, some go by the book whether are still operational, could also be factory installed parts ? Is the impeller back inside its housing ?

Happy Boating

 

[LukeFishWalker]

I dropped the lower unit, pulled the thermostat and used air pressure to blow the jackets out.
Then, used a water hose to force water pre thermostat and post thermostat.
Then, attached the hose to the open water pipe in the mid section.
And, forced water through the tattle tail pesser alternating all 4 locations.
Once I was convinced everything was open, I cranked the engine with the
hose still attached W/O thermostat. The engine was ran for 10 minutes and never got warm.
Then I put the thermostat back in and with the hose still attached, run it again.
The engine never got hot, it got a little bit warmer but not as hot.
So, I re-assembled the lower unit and put the muffs on and with the water on I cranked it.
The temperature never got hot after 10 minutes.
I'm thinking (This Usually Gets Me Into Trouble) that it's possible that something may
have been clogging the pipe or somewhere in the cylinder block.
I am headed to the river tomorrow.

Thanks For Your Time And Patience,
Lukus