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Old 12-09-2016, 00:11   #1
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Re: Help New Guy

Hi Guys,

As a novice with no mechanical experience Im wary about purchase a small 28" Semi Displacement Cruiser with a Volvo Penta. Ive heard the engine previously had some trouble and was smoking alot before having lots of oil changes, air cleaner changes and injection overhaul.

Details below;

Engine: 1985 Volvo Penta Turbo charged Diesel Engine 165hp 6 cylinder.( 2501 hours)TMD-40 "B" with after cooler.

Compression Result:
1-310, 2-310, 3-315, 4-320, 5-318, 6-320

They said last time they tested it # 1 was about 50psi lower.

The boat runs great as far as I can tell but is the motor on the way out ?

My mechanic reading the results told me its past its prime and will last depending on how its run.

To be honest I cant afford a new engine so any advice would be helpful.



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Old 12-09-2016, 00:34   #2
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Re: Help New Guy

Sorry, no turbocharged diesels for me when considering a boat purchase. That's just my personal preference.

On a naturally aspirated diesel I would compare possible replacement part pricing on pumps, impellers, thermostats, injectors, heat exchangers, exhaust components and rebuild kits for several name brand engines.

Then from the comparison results may overwhemingly select one brand over another; or not. Availability of parts becomes key, in my opinion, as models are replaced with newer technology.

If your trusted mechanic summarizes that the powerplant is basicly worn out then I'd run.

Let us know how it turns out

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Old 12-09-2016, 02:48   #3
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Re: Help New Guy

Thanks I will find out about availability of parts.

My mechanic was a bit more diplomatic with no defining response. His comments were:

1) past its prime. ( well its not exactly new)
2) those compressions are not unusual for that age.

He hasnt said its on the way out. I just want to know when I buy it can I get another few thousand hours out of it. It only moves along at about 8 knots at 2500 rpm. I would never need to open it up.

Thanks all the help is appreciated.

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Old 12-09-2016, 09:45   #4
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Re: Help New Guy

No you likely won't get another couple of thousand hours out of it. Marine engines are normally considered at their design life around 3,000 hours. At which point you will need to rebuild it, or replace it. Even with a clean bill of health right now, I wouldn't expect more than another 500 hours before some goes wrong.

This is under normal recreational use btw. If you crank her up and leave the engine running nonstop for a month it would probably be fine.

- If animals weren't meant to be eaten then they wouldn't be made of food.
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Old 12-09-2016, 09:52   #5
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Re: Help New Guy

I'm a gearhead, I love turbos, I enjoy the subliminal whistle.
But they can and often do substantially shorten the life of an engine, add complexity and cost.
They make more HP out of a smaller, lighter engine is the attraction.
How many hours? Nothing is guaranteed, but the compression looks good to me, it is more of an evenness I look for more than just high numbers.
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Old 12-09-2016, 10:35   #6
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Re: Help New Guy

You only have a 10psi maximum difference between cylinders. That's nothing. With care it could have several thousand hours left. If you do 100 hours a year, that's 20+ years. Clean oil and low exhaust gas temperatures will minimize engine wear.
Injector rebuild is a maintenance item in diesels. If there was a burned tip, fuel would flood into the cylinder, causing black smoke and diluting the engine oil, requiring oil changes. But fixed now, right? Injector tips get burnt (enlarged spray holes) from high temperatures caused by running at full hp for long periods. Diesels have a max hp and continuous hp ratings.
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Old 12-09-2016, 10:45   #7
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Re: Help New Guy

Originally Posted by a64pilot View Post
Nothing is guaranteed, but the compression looks good to me, it is more of an evenness I look for more than just high numbers.
+1 on that. Evenness indicates equal wear across all cylinders. Said evenness also indicates that there are no other major issues (other than age) within the engine itself (like bad rings, worn crankshaft bearings and a lot of other things). As A64pilot has stated, the compression looks good. With compression like that it would not be inconceivable to overhaul the engine instead of replacing it and get a few more years out of it.

I've overhauled the 4-liter diesel in the 1986 Toyota Landcruiser in that little pic above my name here every 5-years since I purchased it here in Egypt 16-years ago. Other than the first time, the overhauls weren't entirely necessary, but I was living and working in Egypt's Eastern Desert, North Sudan, and the Eastern edge of the Sahara desert so I had to know my life support system was right. Rig just rolled 500K Kilometers a couple of months back. Maintenance, Maintenance, Maintenance. Learn and understand your equipment....every aspect of it, so that when things go south on you, you can say: "Oh! (Yawn) I got this...."

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