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Nissan NS40D Bad Connecting Rod Bearing

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shieldshigh

New member
I have an NS40D motor on a boat that I just replaced the deck on. It was running great and then bogged down like it was out of gas. Continued to run rough - replaced fuel, fuel lines and filters and decarbed. Then it would start and run smooth - but I thought I heard a pinging. Put boat in water and suddenly was difficult to start but then ran well. It woudl reach 5000RPM+ as always, but pinging became knocking at 3,000 RPM and above so brought back in. Compression in top and bottom cylinders 120, middle cylinder 30. Pulled head and middle piston had been hitting head. Pulled inlet manifold assembly and I can push piston and connecting rod back and forth - bearing between connecting rod and crank is apparently destroyed. I looked in the parts catalog and don't even see the connecting rod or bearing as a seperate item - only the crank assembly.

Is there any hope here? I can't justify putting a ton of money into boat with kids getting ready to start college in a year or so.....
 
with something like this, it is usually cheaper to put a new short block or powerhead on it then trying to make the repairs yourself but they aren't cheap.

chances are high the crank is going to be messed up where the rod connected to it so you are looking at a total rebuild to fix it
 
Thanks for the reply, kind of what I thought. I haven't located any shortblocks for this and not sure it is worth the cost on a motor this old. Any idea what would happen if I removed the middle piston and rod and put it back together? I suppose the crank would be out of balance, but it actually seemed to run pretty decent with only 2 cylinders.
 
it all depends on the crankshaft journal if its scratched or gouged then the crank is history and must be replaced. if the piston has movement its almost certain to have messed up the crank so a repair (thinking positively) would entail replacing the crankshaft and that piston and connecting rod. in most cases a gasket set to rebuild a motor will run you around $200-$250, the crank (if you can find a good used one) maybe $100-$150 or $400-$500 new, the piston and connecting rod new would be around $150 and this is assuming nothing else in the motor is damaged worn out, or broken. add to that a new set of rings for all the pistons for another $100

so this is why I said getting a rebuilt powerhead for around $1,200 is the bet option but you will still spend another couple hundred to put it all back together as a whole motor.

based on your replies I assume the motor is not semi new so I think he best value that motor now is in selling the good parts for getting what you can out of it and put that towards a new motor. depending on condition, the lower unit and the power trim units should be worth at least $500 each and the starter motor $50 and the heads for that motor might be worth $100
 
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shieldshigh said:
Thanks for the reply, kind of what I thought. I haven't located any shortblocks for this and not sure it is worth the cost on a motor this old. Any idea what would happen if I removed the middle piston and rod and put it back together? I suppose the crank would be out of balance, but it actually seemed to run pretty decent with only 2 cylinders.
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it would be out of balance and soon come apart on you but you got nothing to lose by leaving it as-is and running it till it blows up lol.

wouldn't go too far from the launch with it tough
 
That's what I thought - and it's almost $1,000 for the crank assembly if I can even get it. Knowing that the piston would have to be replaced - and that there are some scratches in the cylinder bore - and that the head has marks in that bore from being hit with the piston... I think that keaker is right that it doesn't make sense to try and fix it. Also haven't had any luck finding a replacement short block.

I know the motor will tear itself up if I keep running it like it is, but I'm struggling with the idea of removing the damaged connecting rod and seeing if it will run on the two remaining cylinders. Believe it or not, it was actually running well before I pulled it apart - except of course for the banging sound from the piston hitting the head :rolleyes:
 
well i'll say this, it might be worth it to open her up and see if the bolts on the piston rod cap are lose or one broke off. if that's the case you might be able to replace them and everything will be good to go again inspite of the visual dings. if so you still wont have much compression from that cylinder but at least it wont be banging around In there and you can let it go like it is for however long it may run.

I would NOT take that rod and piston out because you might have fuel air mix bypass going straight into the engine crank case and turn it into a ticking time bomb waiting to explode. but maybe you can disconnect it and see if you can shove it in far enough not to be able to touch the crankshaft

what you are talking about is a whole lot of work and you cant reuse the head gasket if you remove it so leave it alone and whatever you do, do it from the crank side
 
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There aren't any rod caps, and so no bolts. It is serviced as an assembly. Perhaps one well-intended commentor needs to learn about that model before suggesting how to repair it.
 
pvanv said:
There aren't any rod caps, and so no bolts. It is serviced as an assembly. Perhaps one well-intended commentor needs to learn about that model before suggesting how to repair it.
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so you say the crankshaft comes apart in pieces so the rods can be put onto it?

I thought the crankshaft was one single piece as it is for most engines
 
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I havent taken the crank out yet, but I believe the crankshaft is a single piece. I'm guessing it has pins pressed thru the rod and bearing instead of the rod having a cap and bolts. Probably a less expensive way to make it - but also less (or not) serviceable. Tohatsu.net carries the assembly - crank with connecting rods assembled - for ~$1,000 but for a 22 year old engine it probably doesn't make sense.
Good point about the fuel if I removed the piston. I had planned to disconnect the fuel lines from the carb but I don't know if I'll end up with exhaust blowing into the block. I would be afraid to leave the piston in unless I could secure it somehow. If came out and hit the crank while it was running it would be bad.......
I removed the head first in order to troubleshoot. The gasket doesn't bother me as much as the three headbolts that broke around the bad piston.
 
PVANV, can you tell me if the flywheel or anything else has to come off to get the crank out? I have been working on the motor while it is still on the boat, which has been ok up until I tried to split the block - but it doesn't want to seperate on the ends. The motor is probably more of an anchor now, but I would still like to be able to finish getting it apart without doing more damage.
 
keakar said:
so you say the crankshaft comes apart in pieces so the rods can be put onto it?

I thought the crankshaft was one single piece as it is for most engines
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The crank is a pressed assembly; There aren't any rod caps at all. The rod journals are precision pressed at manufacture. Simpler, cheaper, lighter, more reliable, but alas, not independently serviceable.
 
shieldshigh said:
PVANV, can you tell me if the flywheel or anything else has to come off to get the crank out? I have been working on the motor while it is still on the boat, which has been ok up until I tried to split the block - but it doesn't want to seperate on the ends. The motor is probably more of an anchor now, but I would still like to be able to finish getting it apart without doing more damage.
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The block should come apart as in the 2 following diagrams:

002-21038-5_FIG02.jpg002-21038-5_FIG01.jpg
 
shieldshigh said:
That's what I thought - and it's almost $1,000 for the crank assembly if I can even get it. Knowing that the piston would have to be replaced - and that there are some scratches in the cylinder bore - and that the head has marks in that bore from being hit with the piston... I think that keaker is right that it doesn't make sense to try and fix it. Also haven't had any luck finding a replacement short block.

I know the motor will tear itself up if I keep running it like it is, but I'm struggling with the idea of removing the damaged connecting rod and seeing if it will run on the two remaining cylinders. Believe it or not, it was actually running well before I pulled it apart - except of course for the banging sound from the piston hitting the head :rolleyes:
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I have a surprise for you, I found you a replacement crank assembly that is just what you need and cheap enough for your situation:
http://www.ebay.com/itm/Nissan-Toha..._Accessories_Gear&hash=item27e4e62db2&vxp=mtr
 
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shieldshigh said:
Thanks keaker, may be worth a try. Of course if I fix it I have to get the @#*^@# broken head bolts out.
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that's why you keep lots of beer on hand and a loud radio so the kids don't hear you cursing lol

but once you pull the engine off the outboard and set it on a table to work on it, since nothing needs to come out the front you can just split the case open and put everything in from that end and you dont have to touch the head at all. look at the exploded view in the diagram above and you'll see splitting the back case open is all you need to do for this repair.

unless I am missing something, you can just pull the plugs so the pistons move freely then pull everything out by the crankshaft end, put new rings on the pistons and put them on the new crankshaft then slide them and the crankshaft back in as one assembly then tighten everything up and your done without ever removing the heads at all
 
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thanks, that looks just like my old Suzuki DF40

if you need to pull the head on the new 4 strokes, do you have to separate it from the engine holder? thats how my suzuki was and it was a real PITA to work on
 
keakar said:
thanks, that looks just like my old Suzuki DF40

if you need to pull the head on the new 4 strokes, do you have to separate it from the engine holder? thats how my suzuki was and it was a real PITA to work on
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Since these are 4-strokers, the oil pump is cam-driven, and is below the head (and bolted to it), so sometimes you will want the block free of the pan to pull the head. What is an "engine holder"?
 
pvanv said:
Since these are 4-strokers, the oil pump is cam-driven, and is below the head (and bolted to it), so sometimes you will want the block free of the pan to pull the head. What is an "engine holder"?
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that's what Suzuki calls the seamingly pointless spacer plate between the motor and the oil pump housing, Suzuki has two spacer trays that fit between the motor and the oil pan. to be honest it looks stupid and it seams easier if they would have just been cast as one big oil pan and left those two trays out altogether.

see it here:

engine older - http://www.boats.net/parts/search/Suzuki/Outboard/2002/DF40/ENGINE HOLDER/parts.html

oil pump housing - http://www.boats.net/parts/search/Suzuki/Outboard/2002/DF40/OIL PUMP/parts.html

oil pan - http://www.boats.net/parts/search/Suzuki/Outboard/2002/DF40/OIL PAN/parts.html
 
keakar said:
that's what Suzuki calls the seamingly pointless spacer plate between the motor and the oil pump housing, Suzuki has two spacer trays that fit between the motor and the oil pan. to be honest it looks stupid and it seams easier if they would have just been cast as one big oil pan and left those two trays out altogether.
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The MFS40A does have an engine base casting that is independent of the block, if that's what you mean.
 
I was just curious about whats involved in pulling the head off to clean out the water passages that most motors seam to need done a least once in their lifetime.


someone once told me you could use muratic acid mixed 3 or 4 to 1 in water and with the lower unit off, use a bilge pump connected to the water tube to pump it through the engine for about an hour and it would clean and flush the entire water passageways of all corrosion.

have you heard about this practice and what is your opinion on doing it? is it good? bad? works great? doesn't work? will hurt your engine?
 
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