Yanmar Tips

[Compass790]

Originally Posted by Yowieboy

Hello dear experts,

please allow me to hop on this thread to pose a question (or two, actually) related to a Yanmar 1GM10B engine, specifically its (missing) thermostat. Last year, I bought a 25ft Yamaha sailboat in good condition that came with this engine. It's about 18 years old but had only about 500 hours on the meter. The boat had been kept on the hard in a marina for many years and used mainly for weekend and day sailing, with the engine mostly just for leaving and re-entering the harbor. Now I keep the boat permanently in the water and have a somewhat different usage pattern, but I also don't use the engine all that much. Occasional motoring and motor-sailing, with the engine running for a number of hours at most.
I know almost nothing about diesel engines (it's my first boat with an inboard diesel) and I am not mechanically inclined or gifted at all (also not well equipped in terms of tools etc.). So far the only thing I've done is change the oil and oil filter. Thankfully, the engine has never given me any trouble, it starts quickly and runs fine. It does produce a fair bit of vibration and a rather loud kind of metal 'tack tack' kind of sound at idle but at higher revs (sort of midrange, judged by the power, there is no rev counter), the vibrations are much lower, and the sound also settles down. No major complaints there. Okay, so what's the prob, you ask (sorry for the long preamble). Well, I was informed by someone more knowledgeable that my engine apparently has no thermostat, just a bypass hose where one would be (see attached photos). This modification probably was done at some previous point in the boat's life. My question is, how unusual or possibly harmful is this?

And I have another question.
When I said that this engine has given me no trouble, this was true so far, but very recently (last week) I had to motor for about 5 hours at a stretch. During this time, I had to do a bit of evasive action and pushed the throttle to full power for maybe 15 minutes, something which I don't do normally (my usual throttle position is at about 70 percent or so). To my dismay, I noticed that the cooling water (raw seawater cooling) being pumped out of the outlet on the stern suddenly had turned almost black (normally it's just regular water color), and there also was a lot more smoke (or vapor, rather?) than usual. There also was an 'exhausty' kind of smell . After I pulled the throttle back down to its usual position, things returned to normal. Fortunately the engine continued to run fine also thereafter. I've since briefly tried full power a few times, and the same thing started to occur again. (I didn't want to push my luck and do it too long.) Now this has given me pause, especially as some web searching seems to indicate that this could be indicative of a serious exhaust corrosion problem.

Any advice from people in the know will be gratefully received.

Ok Yowie,
first bit of advice I'd give you is to download the operation & service manuals. The service manual is in the CF library & you can probably find the operation manual by googling.

The black stuff is partially burned diesel caused by overfuelling.
This can be caused by blocked exhaust, low compression, blocked air intake,too large propellor, incorrect valve clearances or faulty injector. Do not operate the engine in that overfuelling condition for long as the diesel washes the engine oil off the cylinder walls. Best to throttle back till just below that point.
You should have a thermostat & if you cant get one in Japan where can you get one? The most engine wear occurs when cold so having a thermostat allows the engine to warm up faster.
The tack tack kinda sound could well be loose tappets so I would begin by checking them for correct clearance & the exhaust elbow for carbon buildup. Pretty sure you need to check the exhaust elbow for carbon buildup anyway if it hasn't been done before.You dont need too many tools to do that.
The service manual will tell you how to do those checks.
If you make a video of the noise & the smoke it makes diagnosis easier.
Hope that helps.

[Wotname]

Originally Posted by Yowieboy

Hello dear experts,

please allow me to hop on this thread to pose a question (or two, actually) related to a Yanmar 1GM10B engine, specifically its (missing) thermostat. Last year, I bought a 25ft Yamaha sailboat in good condition that came with this engine. It's about 18 years old but had only about 500 hours on the meter. The boat had been kept on the hard in a marina for many years and used mainly for weekend and day sailing, with the engine mostly just for leaving and re-entering the harbor. Now I keep the boat permanently in the water and have a somewhat different usage pattern, but I also don't use the engine all that much. Occasional motoring and motor-sailing, with the engine running for a number of hours at most.
I know almost nothing about diesel engines (it's my first boat with an inboard diesel) and I am not mechanically inclined or gifted at all (also not well equipped in terms of tools etc.). So far the only thing I've done is change the oil and oil filter. Thankfully, the engine has never given me any trouble, it starts quickly and runs fine. It does produce a fair bit of vibration and a rather loud kind of metal 'tack tack' kind of sound at idle but at higher revs (sort of midrange, judged by the power, there is no rev counter), the vibrations are much lower, and the sound also settles down. No major complaints there. Okay, so what's the prob, you ask (sorry for the long preamble). Well, I was informed by someone more knowledgeable that my engine apparently has no thermostat, just a bypass hose where one would be (see attached photos). This modification probably was done at some previous point in the boat's life. My question is, how unusual or possibly harmful is this?

And I have another question.
When I said that this engine has given me no trouble, this was true so far, but very recently (last week) I had to motor for about 5 hours at a stretch. During this time, I had to do a bit of evasive action and pushed the throttle to full power for maybe 15 minutes, something which I don't do normally (my usual throttle position is at about 70 percent or so). To my dismay, I noticed that the cooling water (raw seawater cooling) being pumped out of the outlet on the stern suddenly had turned almost black (normally it's just regular water color), and there also was a lot more smoke (or vapor, rather?) than usual. There also was an 'exhausty' kind of smell . After I pulled the throttle back down to its usual position, things returned to normal. Fortunately the engine continued to run fine also thereafter. I've since briefly tried full power a few times, and the same thing started to occur again. (I didn't want to push my luck and do it too long.) Now this has given me pause, especially as some web searching seems to indicate that this could be indicative of a serious exhaust corrosion problem.

Any advice from people in the know will be gratefully received.

Compass790 has given you good advice so this is just an expansion on that.

The noise at idle is fairly typical for a 1GM10 as is the vibration however it won't hurt to check the tappets (valve lash).

The thermostat is located under the cover circled in red on the Yanmar-2 picture. You need one. Remove the cover to check to see if it is there or not.

This engine is raw water cooled and as such, it is very important to replace the engine anode as required and certainly after 500 hours it will need replacing if it hasn't done recently. This is critical for a long engine life! The location is shown in the screenshot attached.

It sounds like the exhaust / mixing point (circled in red) may have a carbon build up and this should be checked soon. It is a straightforward job on your engine. This can occur if the engine is used at low power settings for a long time.

Yanmar suggests the engine should be operated at full power for about 10 minutes for every two hours of low power operation.

Get hold on the operation manual and follow what it says!!!

[Yowieboy]

Compass and Wotname, thanks much for the quick response and useful advice so far.

I've downloaded the service manual from the Cruisers Forum library as suggested, and it indeed looks like a very comprehensive reference, although it amounts to a bit of information overload for an utter rookie like me (at least at the moment, past midnight here). I already had a rudimentary operation manual (Japanese) which was on the boat, but I googled and now got the more complete English one from a Yanmar website. I will definitely have to devote some time to the study of these.
When I'll be on the boat next week, I will try to open the cover to check for the thermostat (thanks especially for the red circles, Wotname, very helpful!) and as much as possible check the other suggested items as well.
As Compass rightly assumes, Yanmar parts are not too difficult to come by in Japan, but they do have a reputation for steep prices, even here. And I may try to find someone to check and service my engine, but that also isn't quite so easy. In fact, there's a Yanmar service shop right in the fishing harbor where I keep my boat, but they only handle the large diesels of fishing boats and by their own admission are not very familiar with those playthings in sailboats. When I went there to buy genuine Yanmar oil for my oil change, all they could offer me were 20-liter cans...
Later,

[Compass790]

Originally Posted by Yowieboy

Compass and Wotname, thanks much for the quick response and useful advice so far.
. When I went there to buy genuine Yanmar oil for my oil change, all they could offer me were 20-liter cans...
Later,

You certainly do not need genuine Yanmar oil for your 1GM10. Yanmar doesn't make oil they just use a suitable product, rebrand it & put a big markup on it.
Any 15w-40 diesel oil with an API rating of CF or higher will do. They may recommend CD30 I didn't check but trust me 15w-40 will be fine, millions of diesels under much more severe conditions use it.
I don't know Japan (wish I did) but any auto parts store will have it in 4 or 5 litre containers. Just dont buy the stuff for EGR or catalytic converters.
You dont have to digest the service manual all at once but it's vital if you wont to do a specific job without experience.
Try asking at a marina with lots of yachts if you want to find a mechanic. If you have a too big propellor the mechanic wont be able to stop the engine blowing black smoke without changing it but I would check the other possibilties first as you would think it should have been fitted with the correct size initially.

Thanks Wotname for improving on my post

[Yowieboy]

Thanks for the follow-up. I am aware that genuine Yanmar oil isn't a necessity, and I easily procured a smaller quantity of suitable oil elsewhere, but I just thought if I can find it at 5 mins from my boat, I might as well get it there since at the small quantity that I intended to buy, a certain markup wouldn't have been be a problem.

Regarding finding a mechanic, I will ask around, but unfortunately there's no 'marina with lots of yachts' close to where I am located. Pleasure boating in Japan, while it of course exists, is much less prominent than in the U.S., Europe, or Oceania. I am not too far from Tokyo but on the 'unfashionable' side (although the sea around here is actually beautiful, and there are lots of small fishing ports). Most major marinas catering to Tokyoites are on the other side, some 2 to 3 hours by car, or half a day on my boat across the entrance to Tokyo Bay. But yes, I do go there sometimes, and the trip recently where the black exhaust thing happened was on such a crossing (there's often major ship traffic to dodge, which led to the evasive action).

As for my propellor, I think it's the standard (two-blade, fixed) one that this Yamaha sailboat model that has the small inboard Yanmar comes with originally, so I don't think it's oversized.

I'll keep at it...

[Hunterdog]

So guys...what about the nauseating free spinning prop on the yanmar saildrive while sailing???
Is it a sin to put it in drive to stop the fixed pitch prop??

[Yowieboy]

I finally made it to the boat again and went mano a mano with my Yanmar 1GM, or at least firmly intended to, only to capitulate before I even really started. Not so much because the opponent was all that formidable, but rather because I realized the puniness of my own powers and didn't want to make things worse by incompetent tinkering (after all, the engine does run quite well.)
The biggest obstacle that made me change my mind was the extremely bad access to almost all the things that I, following the kind advice here, intended to check.

First, the thermostat:
The photo in the service manual shows an easily accessible thermostat cover (see photo from manual below) with a thin metal tube running _behind_ the hose connected to the thermostat. However, on my engine, that tube (don't know what it is—shows you how ignorant I am—but it looks pretty important) runs right _in front of_ the hose. To actually remove the thermostat cover it looks like I would have to first unscrew and move that tube (see photo of my engine below). Plus (and this applies to other parts as well) the manual says to discard the gasket when opening the thermostat cover and use a new one when reinstalling. I don't have any of these parts, so I worryingly imagine that just opening and re-closing might result in a worse seal and possible problems that weren't there before.

Next, the anticorrosion anode:
I wasn't able to locate this, due to the very narrow space on the right side of the engine. I imagine one would have to operate by feel, which especially when putting it back probably is easy for a seasoned mechanic working blindfolded and with one hand tied on his back, but I am not that person.

Water pump/impeller:
The water pump cover is partly obstructed by the crankshaft pulley. Removing (and especially reinstalling if removed) seems rather difficult to me unless one removes the pulley first. Leaving the water pump in place and only removing the impeller cover also seems tricky due to the same obstruction.

Exhaust elbow:
This at least seems somewhat easier to reach, but even there, I don't really trust myself to get things back into problem-free order once I've removed stuff.

So, in short, I will be falling back on the idea of having a mechanic (hopefully) familiar with these small diesels check and service the above items for me. Even (or especially?) in Japan, such are not easy to find. (I would guess that significantly more small Yanmar engines in sailboats are actually in use overseas than in Japan itself.) A marina some 4 hours from where my boat is has said they could do it, but I would have to bring the boat to them. Which is probably what I'll be doing fairly soon.


Here's a link to three short videos:
https://www.dropbox.com/sh/7ihap7wos...lqA__Q6Da?dl=0

[Wotname]

Originally Posted by Yowieboy

.............
So, in short, I will be falling back on the idea of having a mechanic (hopefully) familiar with these small diesels check and service the above items for me. Even (or especially?) in Japan, such are not easy to find. (I would guess that significantly more small Yanmar engines in sailboats are actually in use overseas than in Japan itself.) A marina some 4 hours from where my boat is has said they could do it, but I would have to bring the boat to them. Which is probably what I'll be doing fairly soon.
.........

Probably a good idea in your case - no disrespect though.

FWIW, that steel tube in front of the thermostat housing is the pipe that delivers high pressure fuel (2,500 psi) from the injection pump to the injector. Best not to mess with it unless you know how to bleed it after refitting it.

Access to the anode would require the removal of the alternator to make room and they can take a lot of elbow force to undo them.

Likewise removing the crankshaft pulley isn't super easy for the inexperienced.

Hopefully all will go well at the other marina.

[Yowieboy]

Thank you Wotname and also Compass for a private comment. I have absolutely no problem in admitting when I'm out of my depth, so no disrespect taken at all.
Even without doing stuff myself, I've already learnt quite a lot from this thread.

[Wotname]

BTW, that is a very tidy and clean engine - not bad for 18 years old! With basic maintenance and good high power run occasionally, it should last another 18 years!

The wiring is a bit of a bird's nest although it doesn't look as bad as some.

[OloteleMtn]

Paying a mechanic to do the first basic maintenance and allowing you to watch and learn will be a valuable experience; having a shop service manual and access to the parts manual will be very helpful as well, as was mentioned.

[Yowieboy]

Originally Posted by Wotname

With basic maintenance and good high power run occasionally, it should last another 18 years!

I wish the same could be said for myself...

[livbysea]

this is great - for those in the know- any idea why our brand new (electronic) yanmar warning alarm goes off even before starting the engine. and of course this is not totally consistent - esp when the marina guys check it. we turn the key, then the power button, wait 4 seconds and push start - often it works like a charm. but often it triggers an alarm. Oil pressure seems fine, stop cock is open - wondering if it could be a fault in the alarm.... welcome your insights. have left a message at Yanmar - but would love to get off the mooring tomorrow......

thanks!

[Newf1]

Originally Posted by a64pilot

You can’t run a raw water cooled engine that lives in salt water very warm, if you do the calcium carbonate I believe precipitates out and clogs water passages, contrary to what you think often the warmer water gets, the less it will hold in suspension. I believe it’s sugar that confuses us as anyone can tell you more sugar will dissolve in hot water than cold, but that’s not true for everything.

Leave it alone, it’s run fine for decades as is

Not saying that this isn't true but if it is, I'm questioning why Volvo Penta would put a thermostat in their D1-30's that doesn't start to open until 194F and not fully open until 221F. What am I missing? (These temperature numbers were from another post so I'm assuming they are correct)

[Wotname]

Originally Posted by Newf1

Not saying that this isn't true but if it is, I'm questioning why Volvo Penta would put a thermostat in their D1-30's that doesn't start to open until 194F and not fully open until 221F. What am I missing? (These temperature numbers were from another post so I'm assuming they are correct)

AFAIK, al D1-30 engines are coolant cooled rather than raw water cooled. If so, then the VP thermostat range is correct.

The advice given by a64pilot is correct and applies to raw water cooled engines only.