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[Yanmar Transmission] Help me assess first day out on my new (old) boat. I am a bit confused.

acubria

Member II
Finally I got to take the boat out for the first time. The old owner (who is not mechanical at all) and a friend of his came out with me. The friend (who is pretty mechanical) came out to help adjust the stuffing box since I had never done it.

The boat spent the winter in the water. The motor started right away after a New York winter! We went out motoring since testing the Yanmar 1GM (6.5hp) was my priority. It all went fine, I thought. At some point I thought I would test the reverse gear, just to see how it would handle steering backwards. It did pretty well. When I turned the motor back into forward gear, it felt weirdly as if the boat was not moving. I checked the shaft , and the shaft was turning….. a bit more gas….kind of nothing; a bit more gas.... and it started moving again. Weird 10 seconds of confusion…. Old owner and friend were confused too. For a second we thought we had lost the prop.

We went back to the marina after about 30 minutes, I docked the boat backwards perfectly fine into a really tight spot, and that was it. I went home happy, but kind of still thinking about those “weird 10 seconds”….

Today I went back to the boat. A friend came with. We were just leaving the slip when again, it felt as if the boat was not moving…very little thrust....motor is going , shaft turning…but it feels like it has no power…… It was a bit windy and I decided to stay put and do some testing. My friend said he thought maybe the transmission was slipping(?). I checked the transmission oil and it was completely white! Like a vanilla milkshake kind of thing (see photo). I know this is water mixed with the oil. I emptied the transmission and poured new oil 5 times to flush out all that milky stuff. I started the motor again while tided to the slip and put in forward; I could see water moving behind the boat, so the prop was turning. But it still feels like very little thrust.

A few questions for the experts:

1- I think during most of this experience the RPM was provably under 2000 and now I am thinking that maybe it needed to be higher? Also, I kept the whole motor compartment open to be able to inspect it while underway, so even at 1500rpm, it was pretty loud.

2- Could it be that the prop is too small , or too corroded due to lack of zinc? It kind of feels sometimes as if there is no prop.

3- Could the prop be somehow loose and sometimes not turn while the shat is turning? I asked and the prop is not one of those that fold.

4- Would having this milky oil in the transmission make it slip? Does it even have gears??

5- Maybe the e-26 with a 6.5hp , just does not have any thrust ?

6-And where could this water come from?


I have to go back and do more testing. Maybe I just need to get use to this little Yanmar?

Any thoughts would be greatly appreciated.
 

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Alan Gomes

Sustaining Partner
I'm not sure I have answers for everything you are asking, but I do have a few thoughts.

I also have a 1GM in the identical boat. It moves it just fine under most conditions. It pushes me at about 5.3 knots (give or take) in mild conditions, but a bit slower in chop, headwinds, etc.

The biggest puzzle to me is the transmission fluid. That transmission uses straight 30WT diesel engine oil. The transmission takes only about 8 oz. of oil to fill it. Not only does the milkiness indicate a problem but the level is WAY too high--as would be expected if somehow water got into it. But how water would have gotten into that transmission is anyone's guess. I'm stumped on that one. But I do think you need to figure that out. Perhaps you should have a mechanic inspect everything.

By the way: The correct level is for the oil to be right at the groove at the end of the transmission dipstick. The proper way to measure it is to insert the dip stick BUT NOT TO SCREW IT IN. Just insert it until the dipstick will not go down any further but is not screwed in. Then remove it and take a look. Sometimes it is hard to see the oil on the dipstick (i.e., when it's not a milky mess), and if that is the case then you can press the dipstick on its side against a paper towel to see where the oil stops.
 

Alan Gomes

Sustaining Partner
Cruising RPM for that engine is about 2850. It's rated at 3400 continuous and 3600 max. The Yanmar tachs are not all that accurate, however, and could be off by a few hundred RPM. You can confirm actual RPM against what the tach shows by using an inexpensive laser tach such as this one.
 

Dave G.

1984 E30+ Ludington, MI
If the shaft was spinning during the no thrust segment I think you need to look at the prop. If it's definitely not a folder(although the symptoms fit) then possibly the key has somehow sheared or it's loose on the shaft. As far as water in the trans, the only way that could get in there is intrusion from the outside so either the bilge got deep enough to cover the trans or there is a leak directly over it. Of course there is the remote possibility that someone mistakenly put water into it somehow ? With the engine off trans in neutral grab the shaft rotate it abruptly backward and forward and see if something feels loose or if you can hear it clunk. I personally would want to get it up in the slings and have a look at that prop.
 

acubria

Member II
I will get one of those RPM laser tachometer. I am starting to think (and hope) that I just have to get used to how loud the motor is, specially without the soundproofing of the wooden box that covers it. Maybe I am trying to go out to see at 900 RPM ....?
BTY, the prop is a two blade fix prop. Not folding.
I will try to figure out an underwater camera to see what the prop is doing, before I go to the sling.
Could the water come from the raw water system in the motor? The gearbox looks very hermetic to me and I wonder how water could have come into it from the bilge area.
thank you very much for you comments.
 

Jerry VB

E32-3 / M-25XP
Not a transmission expert but on the internet nobody knows you are a dog...

Your transmission is a KM2 per your picture. This is probably "it": http://www.kanzaki.co.jp/en/products/transmission/km2p-1.html

Interesting thread on the KM20A: https://www.cruisersforum.com/forums/f54/yanmar-2gm-km2-a-transmission-fluid-question-16800.html Punch line: you MUST use single viscosity 20W or 30W oil - fancy oil is BAD for the transmission.

Transmissions are not hermetically sealed - they have a breather hole to equalize the pressure - but not many other ways for water to get in. In the picture (link above), it looks like the filler cap has a breather hole. There also is a hole in the back that could be a breather. My guess is that, at some time, water got into the transmission through the breather hole. Has the water been high in the bilge?

Transmissions work via clutch plates which are pressed together by oil pressure supplied by an oil pump in the transmission. There are "forward" clutch plates and "reverse" clutch plates. According to the above link, your transmission uses cone clutches and it says "mechanically engaged" so it might be clamped directly by the shifter arm and not oil pressure that forced the cones together. If this is the case, it might be just a linkage adjustment. Your symptoms (no or unreliable forward, reverse still works) are very typical of clutch problems - forward wears out first for obvious reasons.

Sometimes flushing the transmission oil (which you have done - good) and running it a bit gets the clutches working again.

Sometimes the linkage needs adjustment (forward, in your case) - if the throw is too short, it may not fully engage the clutches.

Sometimes it is very expensive. :-(
 
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Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Do you know what transmission you have? It does sound like a transmission issue.

Diesels are loud, but much can be done with sound insulation when you get around to that.
 

acubria

Member II
Do you know what transmission you have? It does sound like a transmission issue.

Diesels are loud, but much can be done with sound insulation when you get around to that.
It is a KM2-A. I attached a photo of the metal plate on it. All this experience was done with the whole motor cover removed (for better visibility and access) so, yes it was pretty loud in there. I will go back next weekend and do some more testing. thanks for your comments .
 

acubria

Member II
I guess the key is to check if the RPM of the shaft somewhat correlates to the RPM of the motor. If they do NOT correlate, then something is wrong with the transmission. If they DO correlate, then either there is a problem with the prop, or I am just paranoid and too shy with the throttle which would be the best possible problem to have. And it looks like the oil I used is the recommended in the cruiser forums: SAE30 Heavy Duty Straight Grade Oil
 

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Nick J

Sustaining Member
Moderator
Blogs Author
I had a somewhat similar experience during the sea trials for our 35-3. The sea trial was getting the boat from the slip to the yard for haul out. There was almost no thrust in reverse and we couldn't get the boat above 2 knots in forward. It also had some vibrations. I spent the trip discussing possible transmission issues with the broaker and wondering if I was crazy taking the boat to get hauled or for an inspection when I was already sure it needed a new transmission. It turned out to be a heavily fouled prop. If your boat was sitting for a while, it might be worth a look.
 

goldenstate

Sustaining Member
Blogs Author
I guess the key is to check if the RPM of the shaft somewhat correlates to the RPM of the motor. If they do NOT correlate, then something is wrong with the transmission. If they DO correlate, then either there is a problem with the prop, or I am just paranoid and too shy with the throttle which would be the best possible problem to have. And it looks like the oil I used is the recommended in the cruiser forums: SAE30 Heavy Duty Straight Grade Oil
Yes, keeping in mind that your transmission is a 2.62 reduction one, so that 3,000 on the crankshaft tachometer should yield 3,000 / 2.62 = 1,145RPM on the prop shaft. At least, that's how I think it works - someone here will correct me of course if I am wrong.

The milky oil in the transmission seems to indicate an obvious water intrusion / slip problem for the transmission.

It does take some time to build 'way' or speed, especially in reverse. The boat won't immediately be manageable like an outboard.

The transmission is effectively on/off with fwd and reverse. As in, you want the transmission to be ALL THE WAY in forward and ALL THE WAY in reverse when you move it back and forth. Does your transmission cable move freely?

I too have a Yanmar and a two blade prop. The Yanmar manual directs the user to sail with the propeller in reverse when the engine is not operating. The risk is "glazing" the transmission, (at least from what I have read and thankfully have yet to experience.) It's also recommended to pause between fwd and reverse to allow the prop shaft to slow down, but people forget that in tight spaces docking with other fancy boats etc..

It's really easy to forget to put the transmission in reverse, so if people have been forgetting for the past 37 years....
 

Alan Gomes

Sustaining Partner
Concerning how the water got in your transmission: I can't see any way that any of the engine cooling water could have found its way in there. If you look at how the gearbox itself is bolted to the transmission's bell flange that in turn bolts to the engine, there's no real path for water to get into the gearbox. On the other hand, there is indeed a small vent hole in the dipstick. There would have to be to keep the system from getting pressurized. And I can tell you for sure that there is one. But that is a very small hole and you have a lot of water in there. So it's unclear to me how that much water could find its way in, unless the dipstick was submerged below the water for some period of time.

I happen to be down on my boat now because I just changed out the packing for my prop shaft. (My old packing was nearly 4 years old.) I just now measured the height of the dipstick entry point from the bottom of the hull liner. You would have to have had nearly a foot deep of water in the boat to get above that dipstick tube.

Is there any other evidence that would suggest that the boat was partially flooded at some point? For example, is there any water stain along the liner inside the engine compartment that would suggest that water had been in there for sometime?
 

steven

Sustaining Member
simplest explanation is the prop is fouled with something.
For example, barnacles adhered from last season. Or fishing line or debris which could have been sucked into the prop when you backed up.

There is almost no way to keep a bronze prop from collecting barnacles.
 

Alan Gomes

Sustaining Partner
Today I went back to the boat. A friend came with. We were just leaving the slip when again, it felt as if the boat was not moving…very little thrust....motor is going , shaft turning…but it feels like it has no power…… It was a bit windy and I decided to stay put and do some testing. My friend said he thought maybe the transmission was slipping(?). I checked the transmission oil and it was completely white! Like a vanilla milkshake kind of thing (see photo). I know this is water mixed with the oil. I emptied the transmission and poured new oil 5 times to flush out all that milky stuff. I started the motor again while tided to the slip and put in forward; I could see water moving behind the boat, so the prop was turning. But it still feels like very little thrust.
Arturo,

If you come to the conclusion that you want a shop to go over your transmission, I just wanted to let you know that you can remove it without pulling the engine. I can go over the procedure with you if that's something you decide to do.

I have a spare engine and transmission in my garage. I just swapped them yesterday because the transmission that was on the engine in my boat was slightly weeping oil from the rear seal. So I swapped transmissions and now the leaking one is in my garage waiting for me to get around to replacing the seal. So having just done this yesterday, I can tell you that it can be unbolted and lifted up and over the engine from the front, and there is adequate clearance--assuming you can push the prop shaft coupler back about 1.5". The transmission is only a little heavier than a bowling ball, so you can lift the thing with one hand!
 

acubria

Member II
Arturo,

If you come to the conclusion that you want a shop to go over your transmission, I just wanted to let you know that you can remove it without pulling the engine. I can go over the procedure with you if that's something you decide to do.

I have a spare engine and transmission in my garage. I just swapped them yesterday because the transmission that was on the engine in my boat was slightly weeping oil from the rear seal. So I swapped transmissions and now the leaking one is in my garage waiting for me to get around to replacing the seal. So having just done this yesterday, I can tell you that it can be unbolted and lifted up and over the engine from the front, and there is adequate clearance--assuming you can push the prop shaft coupler back about 1.5". The transmission is only a little heavier than a bowling ball, so you can lift the thing with one hand!
Thank you very much Alan for your advice.
I learned a lot from this MUST watch video for Yanmar 1G:
I hope that having the correct oil and the correct amount of it, will solve my problem.

Thanks !
 

Alan Gomes

Sustaining Partner
Thank you very much Alan for your advice.
I learned a lot from this MUST watch video for Yanmar 1G:
I hope that having the correct oil and the correct amount of it, will solve my problem.

Thanks !
Thanks for passing on this video, Arturo.

However, the big question remaining is how you got water in your transmission in the first place. That is still a mystery. It cannot have come from the engine, since there is no path from the cooling system that would let it leak into the transmission. So either someone deliberately put water into it, which would be very strange, or it was submerged above the dipstick for long enough to find its way into the vent hole. Or, there was some kind of ongoing water leak above the transmission that would also allow it to get int via the dipstick vent. But I'm not sure how that could be, granting that the location of the transmission is underneath the cockpit sole where there are no other points of water ingress.

Does the boat show any signs of there having been a high water level inside the cabin?

I guess just doing multiple oil changes and then leaving it with the correct oil and oil level will show you if it is working OK. Just keep an eye on it.
 

Rocinante33

Contributing Partner
I guess the key is to check if the RPM of the shaft somewhat correlates to the RPM of the motor. If they do NOT correlate, then something is wrong with the transmission. If they DO correlate, then either there is a problem with the prop, or I am just paranoid and too shy with the throttle which would be the best possible problem to have. And it looks like the oil I used is the recommended in the cruiser forums: SAE30 Heavy Duty Straight Grade Oil
Aurturo,

When I look at the picture you posted in the first post, it looks like the transmission plate says, 20/30W, not straight grade. The trans may also use a standard (gasoline) engine motor oil rather than the Rotella diesel engine oil. I'm not sure about that.

Also, when correlating the speed of the output shaft vs. the engine crank speed, engine should be 2.62 times as fast as output when in forward gear.
 

Alan Gomes

Sustaining Partner
Aurturo,

When I look at the picture you posted in the first post, it looks like the transmission plate says, 20/30W, not straight grade. The trans may also use a standard (gasoline) engine motor oil rather than the Rotella diesel engine oil. I'm not sure about that.

Also, when correlating the speed of the output shaft vs. the engine crank speed, engine should be 2.62 times as fast as output when in forward gear.
No. The transmission can use either 20 wt or 30 wt. It is a straight grade. 30 wt., readily available at West Marine, is just fine and is what I use.
 

acubria

Member II
Thanks for passing on this video, Arturo.

However, the big question remaining is how you got water in your transmission in the first place. That is still a mystery. It cannot have come from the engine, since there is no path from the cooling system that would let it leak into the transmission. So either someone deliberately put water into it, which would be very strange, or it was submerged above the dipstick for long enough to find its way into the vent hole. Or, there was some kind of ongoing water leak above the transmission that would also allow it to get int via the dipstick vent. But I'm not sure how that could be, granting that the location of the transmission is underneath the cockpit sole where there are no other points of water ingress.

Does the boat show any signs of there having been a high water level inside the cabin?

I guess just doing multiple oil changes and then leaving it with the correct oil and oil level will show you if it is working OK. Just keep an eye on it.
Thanks for passing on this video, Arturo.

However, the big question remaining is how you got water in your transmission in the first place. That is still a mystery. It cannot have come from the engine, since there is no path from the cooling system that would let it leak into the transmission. So either someone deliberately put water into it, which would be very strange, or it was submerged above the dipstick for long enough to find its way into the vent hole. Or, there was some kind of ongoing water leak above the transmission that would also allow it to get int via the dipstick vent. But I'm not sure how that could be, granting that the location of the transmission is underneath the cockpit sole where there are no other points of water ingress.

Does the boat show any signs of there having been a high water level inside the cabin?

I guess just doing multiple oil changes and then leaving it with the correct oil and oil level will show you if it is working OK. Just keep an eye on it.
Alan, honestly the boat feels really dry inside. I definitely think that IF there has been high water in it, it would have been years ago, which would also not make too much sense. I will reach out to the old owner and ask. I think he is honest and maybe will shine light in my gear box conundrum. BTY, thanks for clarifying the oil type I should use in the gear box. Same in the motor crank, correct?
 

goldenstate

Sustaining Member
Blogs Author
Alan, honestly the boat feels really dry inside. I definitely think that IF there has been high water in it, it would have been years ago, which would also not make too much sense. I will reach out to the old owner and ask. I think he is honest and maybe will shine light in my gear box conundrum. BTY, thanks for clarifying the oil type I should use in the gear box. Same in the motor crank, correct?
There are specs for the crank case oil in the owners manual. Probably the most important step is to actually change the oil, which many recreational sailors never bother to do.
 
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