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  #11  
Old 08-01-2012
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Re: How to do compression check?

I don't think it is necessary, but it would not hurt to have oil tested by Blackburn. An oil test will tell you more about the condition of the engine than anything else and they are cheap.
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Old 08-01-2012
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Re: How to do compression check?

Quote:
Originally Posted by miatapaul View Post
I don't think it is necessary, but it would not hurt to have oil tested by Blackburn. An oil test will tell you more about the condition of the engine than anything else and they are cheap.
They actually only tell you anything if done on a schedule with the data trended on a graph. All engines have wear metal present in the oil. The presents of wear metal means the engine works. The oil analysis only shows you the rate of deterioration if you have multiple points of reference over time.(like at scheduled oil changes) 10, 20, or 30 % increase in wear metal in a three months scheduled oil change is normal.... 100% increase in the same amount of time is bad.
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Old 08-01-2012
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Re: How to do compression check?

I think we do demand Formula performance from out engines in the sense that we expect our engines to perform up to spec.

Oil test without a trend won't do much --- maybe if they found metal with part numbers it would indicate bad things but single test won't tell you much.

I've eyeballed the engine. It has 3800 hours and has been in service since 1995 so it isn't showroom clean, but looks fine. Oil on the dipstick looks and smells okay. Coolant in heat exchanger looks fine, no evidence of oil (found that on my 3GM30 which led to the head change). Filters are new appearing so he's probably doing regular changes. One little sea-water leak at a hose fitting. Area under engine clean of stains, oil, etc. Overall the engine looks okay --- not as nice as my engine, but okay.

Seems concensus is a compression check isn't needed. Sure hope you guys know what you're talking about.

Will start it at the survey and see how it does, then run it hard on the seatrial.

Thanks for the responses.
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Old 08-01-2012
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Re: How to do compression check?

3800 hrs is like the equivalent of 200 K miles. Even if treated well that is more than half of life expectancy for a Yanmar.

I would use the hrs alone as a negotiating point.
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Re: How to do compression check?

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Originally Posted by IronSpinnaker View Post

I would use the hrs alone as a negotiating point.
Already done.
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Old 08-01-2012
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Re: How to do compression check?

Hey,

You should ask your surveyor how he will evaluate the engine. When I had my boat surveyed (in 2006) he said he would check all fluids (engine oil, transmission oil, coolant), check all hoses (fuel and coolant), perform a visual evaluation, and then test it during the sea trial. The sea trial included running it at wide open throttle (WOT) for a minute to make sure it didn't overheat (it didn't) or smoke (it did - due to being overpropped), and make rated rpm (it didn't, again because of the prop). He also performed an emergency stop to test the engine mounts.

The glow plugs on my engine didn't work well (bad wiring) so the engine was hard to start. It had 3600 hours at the time of the survey. I wasn't concerned because the engine ran fine, and I only put about 50 hours a year on it. It now has about 3900 hours and has worked very well.

Here is the surveyor's report on the engine:

ENGINE OPERATION
The engine started easily after pre-heat and ran without smoke. The volume of cooling
water was good. There was no oily residue on the water.
Due to the tachometer problems it was not possible to see if the engine ran up to the
manufacturer's specification of 3200 RPM. At wide open throttle the boat speed,
measured by GPS, was 6.7 kts, below the theoretical hull speed of 7.3 kts.
Engine temperature at WOT was 180°F. The temperature differential between the raw
water and the exhaust was 20º at cruise and 30° at WOT. No hot cylinders were noted.
The alternator was charging at 14.35V.
The engine ran without significant vibration. The emergency stop test did not disturb the
engine mounts.


==

Barry
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  #17  
Old 08-02-2012
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Re: How to do compression check?

Quote:
Originally Posted by BarryL View Post

The glow plugs on my engine didn't work well (bad wiring) so the engine was hard to start.

Barry
Just so nobody is confused there are different types of diesel engines. The engine we are talking about in this thread is direct ignition and has no glow plugs.

Many modern small diesel engines are what is called pre-chambered diesel engines and they have glow plugs that pre-heat the fuel/air mixture in a small chamber prior to delivering it to the cylinders. They operate at lower compression and usually will not start if the glowplugs are not functioning.
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Old 08-02-2012
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How to do compression check?

Iron

So if I understand what you are saying, a cold start with a diesel with pre-chambers ( universal M25xp) includes using the glow plugs?

Thanks
DaveM
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Re: How to do compression check?

Quote:
Originally Posted by dsmauney View Post
Iron

So if I understand what you are saying, a cold start with a diesel with pre-chambers ( universal M25xp) includes using the glow plugs?

Thanks
DaveM
Hi Dave,

I have an Universal M25. It has glow plugs and I always use them if the engine is cold. If the air temp is cold, like 50 degrees F, I energize the glow plugs for 1 minute. It the air temp is hot, like 80, 10 seconds of glow plug is enough.

The M25 glow plugs are designed to heat the combustion chamber. No fuel is injected at this time. The glow plug is just a heating element that is used to raise the temperature of the combustion chamber before the engine is running. It's pretty easy to remove a glow plug and test it - just supply 12V and it should glow red pretty quickly. Make sure to use at least 10 gauge wire because it draws a good amount of current.

Last but not least, many boats with M25 engines are wired so that the starter doesn't get power unless the glow plug is powered too. So you need to press both the glow plug button and the start button to start the engine.

Barry
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Old 08-03-2012
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How to do compression check?

Thanks Barry.

What I am asking Iron is the following. When he offers the opinion that a responsive start on a cold engine is a sign of good compression does that include using glow plugs on engines, like the M25xp, that have them. Response from anyone that has experience with diesels would be appreciated.

Goodwinds
DaveM
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