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-   -   Pre purchase survey and mechanical inspection advice? (http://www.sailnet.com/forums/gear-maintenance/62856-pre-purchase-survey-mechanical-inspection-advice.html)

Petar 03-13-2010 09:20 PM

Pre purchase survey and mechanical inspection advice?
 
Hi,

I have had boat surveyed previously but have not had a mechanic look into the engine. I am buying a boat again and it has 1986 Yanmar 3GM30 fresh water cooled with 3000 hours on it. What does a mechanical inspection entail and would anyone have some sort of a checklist what needs to be done / checked. I have spoken to some people and they said just warm her up. Run the boat at Max RPM for 5 minutes and if it does not overheat and no powdering of belts is noted i should be OK.

Any advice is much appreciated

regards/Petar

sailingfool 03-13-2010 09:59 PM

Hire a engine surveyor, he/she will know what to do. 3000 hours is a very experienced engine.

Sabreman 03-13-2010 10:19 PM

I have purchased 2 boats with diesels and have not had a dedicated mechanical inspection on either. In both cases, the surveyor gave the engine a look and spent approx 2 hour on our latest boat. While I would OT discourage an inspection, I do know some things to look at based on personal experience and what I know of the mechanical inspections. For diesels, a list would include but would not be limited to:

1. Cold inspection. Any wet liquid on or under oil pan or transmission? If so, what is it and why is it there.
2. Green corrosion on heat exchanger? If so, may be indicative of a leak under pressure.
3. State of zincs. If they are not even there or corroded away, could be indicative of general maintenance.
4. Belt state. Any obvious rubs or cracks?
5. Oil state. Should be black and not milky. If so, run away.
6. Any grinding or hesitation when starting? Starter could be on the verge of failing.
7. Trans fluid should be pink and the reservoir should be full and not overfilled. If overfilled, could be indicative of a leak that is being neglected.
8. Water streaks around fresh or raw water pumps could be indicative of a leak.
9. New paint? Why?
10. Supply of spares. Could be indicative of general service. No spares could mean that the PO wasn't all that mechanically interested.
11. Run at cruising speed (~2000 RPM). After warmup, should not have a plume of white smoke (if ever).
12. Run at MAX RPM (~3000 RPM). Boat should hit hull speed at about 75% or 80% of MAX. Does excessive black smoke develop? Not necessarily bad (we get black smoke at MAX RPM but I rarely run that hard).
13. Run in reverse. Should not be a lot of grinding noises.
14. Smooth transition into and out of gear while engine is running?
15. Smooth engine sounds? With less than 4 cylinders, may be hard to tell.
16. While running and the engine is fully warmed up, verify that the oil pressure and water temp are per the manufacturer's specs.
17. While running and the engine is fully warmed up, verify that the heat exchanger does not leak. Verify that the exchanger end caps are not leaking. If so, micro cracks could have formed from over tightening (easy to fix) or due to excessive backpressure.
18. Verify that a generous amount of water spits out the back of the boat (verifies that pump works well and that there are no severe blockages.
19. While running and warmed up, verify that there are no pin holes or leaks at the exhaust to raw water discharge Y fitting.
20. Verify that ALL hoses are correct type for the application and in good condition with no rot, cracks, rubs. For this age engine, none should still have the original manufacturer's paint on them (should have been replaced long ago).
21. Double hose clamps on raw water intake lines and exhaust lines.
22. If possible, remove the heat exchanger upstream endcap and verify that there is no debris or impeller vanes blocking water flow. DO NOT do this without owner permission or without a new gasket immediately available.

This is what I can think of for now. I'm sure that there is a mechanic out there who will provide an even more detailed list. I checked Nigel Calder's Diesel book and there is nothing about inspections or survey. Too bad.

Sabreman 03-13-2010 10:21 PM

I agree that 3k hours is very experienced, but should not be considered a deal breaker. Diesels like to run when properly maintained.

jrd22 03-13-2010 10:36 PM

Unless you are very experienced with marine diesel engines I would recommend having a certified Yanmar (works primarily on Yanmars) mechanic inspect the engine. They can generally tell just from starting and running an engine what shape it is in. I would also highly recommend making an oil analysis part of the engine survey, that will tell you what the inside of the engine is like. 3000 hours, if the engine has had scheduled maintenance, is nothing to worry about. Many engines will go 6-8000, or more, before rebuild.

Sabreman 03-14-2010 01:00 AM

Quote:

I would also highly recommend making an oil analysis part of the engine survey
Absolutely. I meant to include that in the list but forgot. I agree that 3k isn't an obscene amount of hours.

sailingfool 03-14-2010 11:17 AM

Quote:

Originally Posted by Sabreman (Post 580373)
I have purchased 2 boats with diesels and have not had a dedicated mechanical inspection on either. In both cases, the surveyor gave the engine a look and spent approx 2 hour on our latest boat. While I would OT discourage an inspection, I do know some things to look at based on personal experience and what I know of the mechanical inspections. For diesels, a list would include but would not be limited to:

1. Cold inspection. Any wet liquid on or under oil pan or transmission? If so, ......Double hose clamps on raw water intake lines and exhaust lines.
22. If possible, remove the heat exchanger upstream endcap and verify that there is no debris or impeller vanes blocking water flow. DO NOT do this without owner permission or without a new gasket immediately available.

This is what I can think of for now. I'm sure that there is a mechanic out there who will provide an even more detailed list. I checked Nigel Calder's Diesel book and there is nothing about inspections or survey. Too bad.

First and foremost, hard to start in cold weather...means poor compression. Only way to tell without a compression test, and the most inportant by far of potential problems.

Sabreman 03-14-2010 01:13 PM

Quote:

hard to start in cold weather
A caveat would be difficulty in cold weather after proper preheating. Neither of our engines would start in cold weather without about 30 seconds of preheat.

I knew that Sailnetters would fill in my blanks! Thanks guys.


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