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Old 29-11-2007, 05:47   #1
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Yanmar 3GM30F

I have a problem and hopefully you'all can help or at least lead me in the right direction. I will try to make this short. This past spring I replaced my shaft and set the Max prop as per the factory. When I moved it to its burth a few miles away I noticed Black sootie smook at the higher RPM's over 2500. I replaced exaust elbow, all filters, injectors. Still have the problem. I think I may have set the prop wrong as I had no smoke before. I just checked the compression and found #1-500 psi. #2-410 psi #3-410 psi. I still need to check the prop But I am concerned with the numbers. Some one told me that no way could I get 500 psi that its not that high new. SO is my gage off?? Do I need to rebuild??
It will do 3800 rpm under no load and Runs smooth and no smoke. Runs fine up to 2400 rpm under a load but after that alot of sooty discharge and its stalls out. Nothing wraped around the prop. prop clean. I am not in a marina so will have to call a mobil guy. What should I have him check? what is my next step? Many thanks to all.
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Old 29-11-2007, 06:32   #2
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Your overloading, put less pitch in the prop.
What are you calling #1? flywheel side or Pully side?
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Old 29-11-2007, 06:53   #3
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I'll just add this:

You can send an email, or call Yanmar, and ask them about your compression. They are sometimes a bit slow about getting back to you (so send the email now), but they have always answered every question I've had for them. Also, if you're near a city of size there should be a Yanmar service shop in town that you can ask.

I checked my service manual (for a 4JH2), and it says that all the cylinders should be within 75% of eachother, from the highest to the lowest. 410/500 is 82%, so if 500 is on the high side, the others are as well, because the range is fine.

But according to the 4JH2 manual, your readings aren't too off as far as ranges go. However, it's giving me example readings of 115psi and 120psi, but that could very well be because of engine design.

There are some people on here a lot more knowledgeable than myself about diesels, but that's what I can gather from my manual for you :-)
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Old 29-11-2007, 11:28   #4
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Don't worry about the engine. As Pat has already stated, you have way over proped. Sort out the pitch. You are a good 3" to maybe 4" over based on what you have said.
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Old 29-11-2007, 11:49   #5
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PUlly side. Thanks for the quick response. I guess I missed a notch or two. Will pull and repitch. Many thanks
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Old 29-11-2007, 12:10   #6
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A few more questions.
What is the installation angle? is the back lower than the front?
What is the MAX rpm you can get in forward? THat's total max, not when the smoke starts?
Has the engine ever had a water reversion or been hydrolocked then cleared?
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Old 29-11-2007, 14:30   #7
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The back is lower a little. I never hydro locked while I had it But before I dont know. Before it started smoking I could do 3400 rpm Now I can get close maybe 3K but sounds werd and has lugged to a stall. But under no load will do 3800 and no smoke.
Anything else??? I do want to know. Thanks for the help Al
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Old 29-11-2007, 17:29   #8
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Pitch wise I'd adjust it back for 4", what ever that turns out to be in deg.
410# is low but also might be why your having to compensate with pitch. Adjust the valves and see if the compression comes up. How many hours on the engine?
what is a normal operating event for this engine?
What I'm asking is how do you operate it at any normal outing. Idle time?, what speed do you motor? cool down time? time motoring under load.....just describe an average outing.
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Old 29-11-2007, 18:38   #9
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It sounds like you changed the setting on the prop.

The engine is overloaded.....reduce the pitch

It is too bad you spent all the money on the other things....

I see this quite a bit when people change from two blade to three blade props
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Old 29-11-2007, 19:55   #10
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It is easy to get the Max prop clocked wrong. There are three alignments that have to happen (at least on the two blade).

Each blade pinion needs to be clocked to the drive hub and then the drive hub needs to be clocked to the drive shaft.

Easy to mess it up. I d/l'd the Max Prop manual to do mine. We are probably slightly overpropped as we don't quite get to max RPM but no smoke so I'm living with it for now.

As grandma says - "Go Back and fix the last thing you f***ed up before doing a science project..." My grandma was a merchant marine - LOL
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Old 29-11-2007, 21:04   #11
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I made a few trips but sadly have not used it much in two years. Fixin stuff, run it at dock every 6-8 weeks but has gone months with out. I have solar so dont use it to charge the batt. I probbly ran it to slow at 2800 rpm. It came with the max prop. I just checked with them tonight and was given several settings and when I get it off I will check to see what I set it to. It only has 1500 hours 1996. I set the valves but found some conflicting info one book stated .002mm another was .2mm I dont remember what I used. I will recheck when I find the right one.
What do you think about a leak own test? I would like to get by with just redoing the head at worst. I think the repitching will help alot, But still concerned about the PSI.
Keep the questions comming!!!!
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Old 29-11-2007, 21:38   #12
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From the manual

valve clearance is .2mm or .008 in
compression range is 390-470 psi
there should be no more than 43psi range between highest and lowest

I am sure you are using a diesel engine compression tester i.e. it has a special insert that you install like an injector. A gasoline engine compression tester will not work

Also have you done a wet compression test?
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Old 29-11-2007, 22:21   #13
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yes for all except a wet test? I would guess I put some diesel in the cylinder before the test? other? how much?
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Old 29-11-2007, 23:52   #14
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Quote:
and has lugged to a stall.
Sorry, I don't understand this term. Do you mean it slowed down and came to a stop while you had full throttle on??

With a compresion test, you do it in two ways. First dry and note pressures, then apply a small amount of oil into the cylinders and repeat. This will tell you a little about the condition of bore/rings. A leakdown test is a better way at working out what is worn where and how bad.
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Old 30-11-2007, 01:50   #15
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There are also hot and cold compression tests. i.e. hot engine and cold engine

Also it is important how you bring the cylinder up to TDC unless you are doing a cranking compression test.

A very accurate test is a differential pressure test. You use compressed air which is passed through a calibrated orifice. Upstream of the orifice is a pressure guage. Downstream of the orifice is a second gauge. The air is then directed to the cylinder head and the piston is positioned at TDC on the compression stroke. The pressure drop across the orifice is directly related to how much is leaking across the valves and rings. It is very accurate.

You can also do some interesting diagnostics with this method and it is possible to identify broken rings, bad valve seats and even the ring step that develops over time at the time of the conpression stroke. If you've got a bad valve you can hear it immediately in the intake or the exhaust pipe.

Bottom line though is that in order to make sense of the numbers you have to do it the way the manufacturer says to do it otherwise you can't use his numbers.
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