looking for a nissan/tohatsu guru

[millacd]

I'm having some strange cooling/water pressure problems on one of my nissan 120s. I have not diagnosed the problem yet, but I have the powerhead off, and have some very specific questions about the cooling system paths. I joined this forum because I saw some online posts from a guy called "TOHATSU GURU" and he sounded like someone that could help me out. I have another thread going on this topic on another website (troubleshooting a pair of nissan 120's (WITH PICS) - The Hull Truth - Boating and Fishing Forum) The short of the problem is:

water stream is weak. a properly operating thermostat causes the stream to be weaker. The thermostat in there now is stuck open, and this i believe causes the engine to run cool. I left the old thermostat in because the new thermostat dramatically decreases the pee stream.

There is a water leak from near the top of the midsection. I have pics of this in another thread, but I really need an expert to help me figure out the specifics of water flow in this area. The shop manual is pretty vague.

I have dropped the foot and removed the powerhead, the water pump was in basically mint condition (visibly looked good, and about 40 hours on the pump from what previous owner said, and what I have put on it)

The gasket between the engine base and powerhead was good.

 

[Bronlonius]

Re: looking for a nissan/tohatsu guru

Not sure of your location, so maybe this is not relevant, but have you by chance been in waters infested with zebra mussels? I've been hearing a lot of stories about those things getting into cooling systems when they are small, and then growing bigger and clogging them up.

 

[Sea Rider]

Re: looking for a nissan/tohatsu guru

Welcome to Iboats,

Losing water throughout the middle section will decrease overall water pressure inside engine. With a thermo in open state engine will take way longer to heat to correct temp, much worst runing on cold water. Buy a new thermo, must have one in perfect warming/cooling operation. Were water pump pipe rubber grommets found in good shape, that is not dried, worn out, properly seated ? When you say poor water streem, you mean through pee hole or at back of engine ?

Happy Boating

 

[millacd]

Re: looking for a nissan/tohatsu guru

Welcome to Iboats,

Loosing water throughout the middle section will decrease overall water pressure inside engine. With a thermo in open state engine will take way longer to heat to correct temp, much worst runing on cold water. Buy a new thermo, must have one in perfect warming/cooling operation. Were water pump pipe rubber grommets found in good shape, that is not dried, worn out, properly seated ? When you say poor water streem, you mean through pee hole or at back of engine ?

Happy Boating

The water pipe grommets (if they exist) have not been inspected yet. Those appear to be below the engine base, which I have not removed yet. I removed the powerhead off the top of the engine base, and stopped there because I found a hole maybe 6mm in diameter that appears to be designed to drain water into the compartment where the driveshaft goes down between the shock absorbers. This is the compartment that is leaking out from under the large rubber grommet labeled #7 in this diagram. I am flummoxed as to why the engine would be designed to drain water into this compartment (the compartment between the powerhead and engine base which contains the shock absorbers and driveshaft)

For those that are curious or want to help, there are more details in the other thread in my original post, but I did not want to flood y'all with information

 

[Sea Rider]

Re: looking for a nissan/tohatsu guru

Through that hole some part of the water circulating through lower crancase is delivered there to clean and cool down internal exhaust located at middle leg, water with fuel/oil leftovers are drained through prop. If you have removed crankcase from it's base will need a new base gasket, clean well both mating surfaces, torque tight new gasket or wil see water exiting and wetting lower pan. You could seal the large lower grommet with silicone to make it waterproof.

Happy Boating

 

[TOHATSU GURU]

Re: looking for a nissan/tohatsu guru

The pee stream is just one indicator of a potential problem. IE If the stream is good, no problem...If the stream is not good, MIGHT be a problem. So, is the engine actually overheating? If not, you are worried about nothing more than sediment build up at the port. And, no a properly operating thermostat does not reduce pee stream pressure. Based on what you have posted I think you are trying to fix a non existent problem.

 

[millacd]

Re: looking for a nissan/tohatsu guru

Through that hole some part of the water circulating through lower crancase is delivered there to clean and cool down internal exhaust located at middle leg, water with fuel/oil leftovers are drained through prop. If you have removed crankcase from it's base will need a new base gasket, clean well both mating surfaces, torque tight new gasket or wil see water exiting and wetting lower pan. You could seal the large lower grommet with silicone to make it waterproof.

Happy Boating

Thanks for the input. I had thought about sealing if with something, but I wasn't sure if that was okay to do or not. My other 120 doesn't leak water out from under this grommet, so that's why I initially suspected that could be a cause.

I have ordered the appropriate gasket and it should be here this week. At first, I thought that this "leak" coming from under the grommet might be contributing to my lack of stream pressure, but after looking at the design with the powerhead off, and realization that water is designed to enter that area, I now imagine it has nothing to do with the loss in stream pressure. Perhaps there is a clog somewhere. I imagine if there is a clog, the backpressure caused by the clog could maybe be causing excessive water to enter the drain I mentioned which then could be causing the "leak" under the grommet.

 

[millacd]

Re: looking for a nissan/tohatsu guru

The pee stream is just one indicator of a potential problem. IE If the stream is good, no problem...If the stream is not good, MIGHT be a problem. So, is the engine actually overheating? If not, you are worried about nothing more than sediment build up at the port. And, no a properly operating thermostat does not reduce pee stream pressure. Based on what you have posted I think you are trying to fix a non existent problem.

Unfortunately, there definitely is a problem, but the solution remains a little mysterious. I've got twin 120s and I had difficulty starting this one engine (starboard side) after I shut if off after a 35 mile run. I usually don't have problems starting these engines when they are cold. It took me about 20 minutes of trying different things to get her started, and this happened 3 times, twice on the water, once while flushing.

The differences I've observed between the two motors (other than starboard having difficulty starting while warm) are that the starboard motor pisses weak, and the water it pisses is noticeably colder than the other engine. The water that leaks out of the rubber grommet by the engine base is also cold. Also, the exhaust manifold on the starboard engine runs colder than the exhaust manifold on the port engine. I have not taken any detailed temp readings. Compression is great however, 150 all around. I have not ripped the plugs out of the port motor yet to compare, but the starboard motor plugs do appear at least mildly to moderately carbon fouled. If i remember correctly, I think that's a possible consequence of an engine running too cold.

When I took the thermostat out of the starboard motor (ran it on muffs without a stat in), it ran and pumped water very similar (perhaps slightly stronger stream) to how it normally does as stated above.

When I put a new stat in, the pee stream was weaker, and the exhaust manifold warmed to roughly the same temperature as the port (good) engine. I don't know why, but this definitely happened.

I know the stat in it is bad because the engine warms differently/quicker/better with the new one in, so I'm getting another one.

Does the above water tests also indicate a blockage somewhere? and does my description help narrow down where it could be?

I agree I have chased a problem into an area where there doesn't not seem to be a problem (the driveshaft housing area), but there is a problem somewhere. I originally thought the leak from under the grommet could cause a drop in water pressure and weak stream. After looking in the area, I don't think that's the case. I now think that a blockage somewhere could cause backpressure to develop and cause excess water to be pumped into the hole that drains to this area behind the grommet, and this causes the appearance of a "leak."

Tohatsu Guru, did you see my pics on the other thread showing where the leak comes from? Thanks for the help

 

[pvanv]

Re: looking for a nissan/tohatsu guru

Try a new wp kit, even though your old one looks "ok".

 

[millacd]

Re: looking for a nissan/tohatsu guru

I have some specific questions in bold for those who may want to help me:

What is the bolt labeled number 23 in this figure? It was loose after I took off the powerhead. I'm not sure it's important, but it is loose, and I haven't done anything to it.



On an unrelated note, the rubber grommet labeled number seven in this picture below appears to be slightly displaced where I am observing the leak from. Is it possible that that is causing my leak?



Here is a picture of the leak in my engine. A little more water flows when the engine is on. You might be able to notice a slight curve in the grommet because it seems to be jammed in the lower cowling a little funny.


Here is a picture of the grommet from above. As you can see, there is a speck of light indicating where the leak comes out of. Also, you can tell that water circulates from the hole I marked with a red arrow in the photo below the next one. Where is it supposed to drain to? down the driveshaft? It doesn't make sense to me, and I'm not sure how much clearance there is around the shaft, but I guess water could drain down it if it needs to. Right now, the water coming from the hole marked with the red arrow seems to be draining out from under the rubber grommet.



Here is a photo of the same compartment pictured above, but instead, this photo is of the "ceiling" of the compartment. It is basically the bottom of the powerhead. By tracing a long twist tie through the canals, I have deduced that water from the riser tube/engine base enters the area marked by the yellow arrow, then continues onto the exhaust manifold, and other areas. ALSO, the water makes a hard right turn through the block through the canal marked with green arrow and continues to the hole marked with the red arrow. The water then drains into the area pictured above where the shock absorbers and aforementioned black rubber grommet are. This MUST be contributing to the leak under the grommet.



So is the leak being caused by a defective grommet? or a blockage somewhere further down the water lines causing excessive water to enter this area? or maybe both?

As someone mentioned above, is it possible to seal the grommet with silicone without any fear of consequences? I don't think it would be a good idea to have a whole lot of saltwater backing up in the area near where the driveshaft meets the crankshaft. I thought it might increase the chances of the driveshaft seizing to the crank because of corrosion.

 

[Sea Rider]

Re: looking for a nissan/tohatsu guru

Some Points :

1-Bolt 23 seems to hold exhaust muffler agains upper base, if loose torque well, including all other bolts that holds exhaust in place too.

2-Rubber grommets with heat can be deformed and not seat as when new. Buy a new one if found so.

3-Clean all water paths (holes) seen at engine base, can poke them with a wire, wooden stick, compressed air, etc.

4-When assembling back head, slight grease with water resistant grease shaft splines, will avoid head being seized to shaft when removing again.

5-If suspecting having a salt blockage, remove leg and connect a proper diam hose onto lower water tube, remove thermo, screw thermo lid back, flush head for some minutes , if having good pressure at hose, much better. Place back thermo.

6-Clean well all mating surfaces before head is seated onto pan, torque well all head lower bolts located under pan. Probably your base gasket is burned, dried, cracket and lets water out. If so, placing a well torqued one will solve the issue.

Happy Boating.

 

[millacd]

Re: looking for a nissan/tohatsu guru

Some Points :

1-Bolt 23 seems to hold exhaust muffler agains upper base, if loose torque well all other bolts that holds exhaust in place too.

2-Rubber grommets with heat can be deformed and not seat as when new. Buy a new one if found so.

3-Clean all water paths (holes) seen at engine base, can poke them with a wire, wooden stick, compressed air, etc.

4-When assembling back head, slight grease with water resistant grease shaft splines, will avoid head being seized to shaft when removing again.

5-If suspecting having a salt blockage, remove leg and connect a proper diam hose onto lower water tube, remove thermo, screw thermo lid back, flush head for some minutes , if having good pressure at hose, much better. Place back thermo.

6-Clean well all mating surfaces before head is seated onto pan, torque well all head lower bolts located under pan. Probably your base gasket is burned, dried, cracket and lets water out. If so, placing a well torqued one will solve the issue.

Happy Boating.

thanks for the tips.

any idea what i need to remove or how hard it would be to replace that rubber grommet #7? The silly piece of rubber is like 45 bucks and shipping. would it be okay to put silicone on the bottom of it to make it flush?

When I removed the powerhead, the gasket was basically in like new condition. I was hoping to find a bad gasket, but it looked perfect. I've already have another one though ready to put on.

I tried the hose thing you mentioned already, but I will remove the thermo next time. maybe I have already dislodged my clog by the hose method, and don't know it yet because my powerhead's off.

 

[Sea Rider]

Re: looking for a nissan/tohatsu guru

Sorry can't help you too much as I only work with Tohatsu 2 strokes up to 40 HP engines. Slicone won't harm grommet, just apply a thin coat, let cure and test.

Was the removed gasket the thick paper one or the new model that has a aluminum layer in middle sandwich and a black coat on both sides ?

Removing thmo and closing lid will assure full water circulation through all water passages without restrictions while flushing at pressure through lower water pipe.

Happy Boating.

 

[millacd]

Re: looking for a nissan/tohatsu guru

Thick paper one.

before I removed the powerhead, I did run the engine without a stat on muffs for a little bit, and the stream was improved. not sure why or how, but it happened. a new stat put in made it **** even weaker that it normally did, but the engine did get up to temperature faster that way.

Interestingly, this motor that pisses weak usually pisses colder than my other motor. go figure.

There are a couple passages I want to shoot water into, I'll try flushing it out with water, and maybe some vinegar, but other than that, I want to get a new stat in and put it back together.

I hope I still don't have problems after that, but because I haven't really fixed anything, I fear if I put it back together as is without finding something, I will be right back where I started with the leak, and the weak stream still there.

 

[millacd]

Re: looking for a nissan/tohatsu guru

Another thing that might be of significance:

The hole marked by the red arrow in the pics above that is supposed to drain water into the area that leaks (where the driveshaft meets the crankshaft and the shock absorbers) was mostly clogged by salt when I disassembled the engine. I imagine now that even more water could drain into this area now because the hole is more opened up. I imagine that even more water could potentially leak out from under the grommet now. That doesn't really help me fix my problem, but it does lead me to believe there could be another salt clog somewhere. any product other than vinegar or salt-off I could try to use to bust up salt clogs I can't see? Any foolproof method to make sure there are no clogs that I can't see?

 

[Sea Rider]

Re: looking for a nissan/tohatsu guru

Paper gasket could be all the culprit, new one should have black fondant material to sides and a thin alum sheet in middle, does not requires gasket sealer, just place onto lower pan and torque very tight with wrench.

A thermo installed on egine will need to much water pressure to open/bypass water for head passages to be flushed, without one, a walk through the park. When you reffer to poor peeing, is that through peeing side wtater port, known as a water discharge indicator, or the larger discharge water port located at rear upper leg if your engine happens to count with one ?

You can poor vinager direct on all water holes and passages, let soak, mechanically remove salt layers or crusts if found, don't dilute vinegar, it's only 5% acidity at the most. Clean well both pan and engine mating surfaces and torque gasket to specs, place a new thmo, engine will refrigerate much better and run happily.

Happy Boating

 

[millacd]

Re: looking for a nissan/tohatsu guru

the water discharge indicator. I already checked the water indicator hose, and hole, and exhaust manifold. no clogs found there. I'll try vinegar when I can, and I'll see if I can borrow an air compressor.

 

[Sea Rider]

Re: looking for a nissan/tohatsu guru

Millacd,

How old is that engine, was it second hand or new when you bought it ? If you have found salt obbstructions under pan area, expect to find some salt layers, crusts inside cylinder head. If you're mechanically inclined, could take advantage having crankcase already removed from base to perform a water passages maintenance inside cylinder head along piston & cylinder head complete decarbon. If done, will need a new head gasket though.

Know it's more work and more expensive in parts than same done to a 2 cylinder engine, but it's the way to go, remember OB's don't use glycol as in cars, no matter what yo do salt layers, crusts will be formed inside water passages. Having all of them in inmaculate clean condition will assure correct cooling temp as when engine was out of the box...

Happy Boating

 

[millacd]

Re: looking for a nissan/tohatsu guru

they are both 1999. The only significant salt buildup I've found was in that hole marked with the red arrow i keep mentioning. The other engine pisses like a racehorse and the intake filters were in great condition on both engines.

I'm not sure if I'd like to risk breaking a bolt off on the head. I am usually pretty lucky (careful actually. I've found luck have precious little to do with it) when removing bolts, but I let my over-eager dad tackle the exhaust cover, and he broke a couple off. We're struggling through them, but we're making progress. My new policy is I'm the only one that touches bolts on my blocks that way if I break it, I can only get mad at myself.

What is the best way to make sure there are no clogs I can't see without taking anything more off???

Right now, I've got the powerhead off, exhaust cover off (the outside cover, not the inside one yet), and thermo cap off. I already have exhaust gaskets ordered. With the thermo cap off, if I squirt water to the block, it drains out pretty quickly. If I shoot it into the head cover, it also drains out pretty quickly. Does that indicate those passages are pretty much good to go? Should I try shooting compressed air down in them?

... Still haven't had a chance to squirt vinegar in the passages yet.

 

[Sea Rider]

Re: looking for a nissan/tohatsu guru

Is not that I want you breaking bolts inside engine or having your cylinder head removed without needing it, but that you don't know yet. The only way you could break a bolt's head is if threads are severely seized salted. The best is to apply a thin coat of proper water grease to all nut threads when assembling parts back and torquing to specs important ones with a torque wrench.

Once bought a inmaculate Evi 15 HP engine, to find some days latter poor peeing and overheat, changed impeller, bettered a lot, but at wot engine kept overheating. What the heck, removed cylinder head, oh boy lots of salt layers and crusts, vinegar was squirted on all water passages, let soak, with small screwdriver mechanically removed all salt layers and crusts, put a new head gasket and thermo and that made the whole peeing & cooling difference. Previous owner did a very lousy or no flushing at all after using the engine.

You can shoot vinegar, water, compressed air even bullets, will remove salt layers but probably not severe salt crusts though which might limit correct water flow through main water passages. Check the number of important water passages inside, and that's just a 2 cylinder engine.

Happy Boating