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HELP PLEASE - Low Oil Pressure

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al ralston

New member
I bought a 2001 Sundancer 260 last July with a 5.0EFI/Bravo III.
After mechanical survey and purchase, I questioned local mechanic about low RPM (max 4000...should be 4500). Long story short, water in cylinders...had to rebuild heads, new manifolds, risers, etc...total $5K. Boat ran well for another 30hrs at end of season.
Launched this year and ran great until I backed down to idle....oil pressure dropped and alarm went off. I have changed oil and filter twice, confirmed with mechanical gauge, etc. and finally conceded to turn it over to mechanic (not the same one as previous company went out of business this winter!). This mechanic (good reputation and recommended) has taken the engine out and states that there is a little debris in oil pan and some wear on oil pump, but nothing conclusive. He is suggesting that I have a worn bearing in the crank assembly and the best option to assure fix is to replace the long block (or engine all together). I am going to ask him to do two things before conclusion:
1. replace oil pump and run engine to see if it resolves problem.
2. have oil analyzed for metal shavings indicating worn bearing.
Can anyone add to my basic understanding here? I admittedly have limited knowledge and am trying to avoid another huge bill if at all possible.
Thanks for any help offered.
Al
 
what oil you running?

replace sender with known good mechanical gauge and verify the pressure readings before panicking. Senders can get a bit of sealant in them especially after a head repair and read goofy.
 
Thanks. Running 25/40 oil as recommended. As mentioned, I did verify with mechanical gauge (through full range of RPM and at various stages).
Also, a few more details....engine starts and runs perfectly (no noise, no hesitation), good oil pressure through full range of RPM (about 10PSI per 1K RPM). Only when dropping down to idle after heating up do I have the low oil pressure. Once I put in gear and run back up to 1K+ RPM, pressure inches back up above alarm level (around 5+ PSI).
Thanks for input.
 
Bt Doctur said:
any chance it has a hi-volume pump
Click to expand...
I don't think so.
Just got estimate from mechanic. Course of action is to replace pump and see if they can recreate low oil pressure with engine out of boat. If not, replace engine and run to see if resolved. If not (in or out of boat), then replace long block. No guarantee on oil pump even if it appears to be resolved. So, chance I can have pump replaced and everything looks good, then still have problem once boat is launched ($2700) - then would still have to pull back out and replace engine ($7000). Does this sound legitimate?
 
al ralston said:
1..... Course of action is to replace pump and see if they can recreate low oil pressure with engine out of boat.

2..... If not, replace engine and run to see if resolved. If not (in or out of boat), then replace long block. No guarantee on oil pump even if it appears to be resolved. So, chance I can have pump replaced and everything looks good, then still have problem once boat is launched ($2700) -

3..... then would still have to pull back out and replace engine ($7000). Does this sound legitimate?
Click to expand...

1.... If you pull the engine for an oil pump replacement.... why would you NOT remove several main bearing caps and inspect?????
You'll be right there in the neighborhood!

2.... Did you visit this shop while wearing your $5,000 suit and while driving up in your Bently?

3... I would love to replace your engine for $7K.


Ask for and be willing to pay for proper diagnostics up front.
Have the work performed only after reading and signing a work scope "quote" (not an estimate) that clearly defines that the work scope will indeed correct the problem.



If you do over-haul this engine.... I would NOT go back together with these.

811898=41178-Dished%20Piston.jpg



Go with a much better suited piston for SBC Marine use.

images
 
Thanks Rick - that's very helpful.
I made it clear I am not a rich man - don't think they really care though!
If I agree to the work, the estimate will be a work order signed before work is resumed. My problem is that they already have the boat (on their trailer at their shop) with the engine out. It is tough to say I want a second opinion or to get an estimate from someone else and have the whole project moved. I feel they have me by the short hairs and the best I can do is to ask a lot of questions, make a decision and hold them accountable.
I will ask them about removing the bearing caps and inspecting - though they did say they checked what tolerances they could and found no movement.
I really appreciate your input.
Al
 
Al, I'd say yes.... you have gotten yourself into a situation whereby they do have you by the short hairs.

Check with MichiganMotors as to their cost for a new long block engine, or perhaps a complete engine.
These would be the same as though purchased through Mercruiser.

Check with several other shops as for a cost comparison to R&R a long block.

If your engine is out now...... you're almost half way there!

And again.... try your best to avoid an estimate!
You will do better with a quote.


.
 
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