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Old 09-03-2017, 12:32 AM   #1
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Default 1998 Maxum 2300SC low oil pressure at idle

I picked up a Maxum 2300SC about 8 weeks ago, which has a merc 7.4L MPI 454 in it and was running great for about 20 hours.

We recently had an issue where we lost reverse, and had the marina mechanics repair since the issue was on the lower/engine side of the throttle cable. I mention that because the boat had no issues in ~15+ outings, then had 1 successful "short" trip(about 45 minutes) after their repair.

The 2nd trip, the boat stalled after about 60 minutes on the water, the driver at the time thought it was low oil so they added a quart which I don't think was necessary but the boat wouldn't start back up for him without blasting the alarm so it was towed back to the dock.

Its current situation, it will start and initially the oil pressure is at about 20, but drops until it hits ~5 as it warms up and the alarms goes off. It's not the pressure and the mechanic thinks 2 of the cyclinders need to be reworked but ultimately suggesting a new engine.

I'm obviously going to get a second opinion or third, but thought I'd reach out here for suggestions on any simple things the mechanic could have done by mistake that we can look at?

I've changed the oil/filter to ensure clean and correct amount but that is it so far. The engine starts, and sounds as it always has maybe even a little better after the oil change. The pressure goes up with the RPMs as well.
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Old 09-03-2017, 03:04 AM   #2
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Welcome aboard

Do you know how many hours are on the engine?

Last year my 5.7 lost oil pressure while underway, dropped to about 20 at 3200 and engine started knocking. When I stopped the pressure was 5 psi. I made it back to the marina but the main bearings were shot. I bought a new long block.

Install a mechanical oil pressure gauge by adding a tee at the sensor to verify the pressure.

Any signs of oil in the bilge? If so rear main seal could be shot.

The story about two cylinders doesn't make sense. This is a major loss in oil pressure. Rear main seal, oil pump, bad main bearings.
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Old 09-03-2017, 12:16 PM   #3
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Thank you for the thoughts/comments!

There are ~590 hours on the engine and it was maintained regularly by the Marina - and it does appear that way.

Nothing in the bilge, always clear/clean water. I did the oil change and used Quicksilver 25w40 per the book - wondering if a straight 30 or other oil may mask the symptoms? I don't want to hide the issue, just trying to figure out how it went South so fast... I know, "welcome to boating"

Yea, the story doesn't add up. This Marina also raised their price on slips from $120/ft to $150/ft next year so I'm questioning their recommendations now.
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Old 09-03-2017, 12:31 PM   #4
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Well my oil pressure went from about 50 to 20 in a minute, although I was hearing some low noise prior it was a flip of a switch when the pressure dropped and the loud knocking started. I have seen this happen in my car days a few decades ago.

That is a bug jump in marina Fewster but when was the last time they raised them? My marina has been increasing about 2 percent every year.

Remember a marine engine is under heavy load all the time where a car engine costs a large amount of the time.
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Old 09-03-2017, 12:37 PM   #5
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Only way I can think to have caught thus earlier would have been an oil analysis which would have indicated traces of bearing metals in the oil.
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Old 09-04-2017, 01:21 AM   #6
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Could low gear drive oil cause the alarm on this model?
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Old 09-04-2017, 11:37 AM   #7
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Quote:
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Could low gear drive oil cause the alarm on this model?
Yes the alarm can be sounded by one of three things, oil pressure, low gear lube or over heating. Each of these has a sensor switch and all three are wired in parallel so if any one switch closes it completes the circuit path to ground turning the alarm on. Note these switches are separate from the sendors that the helm gauges use. Since you alarm sounded and the oil pressure gauge was reading low that is two sendors giving you a warning so I would assume it's a true fault. To isolate a bad alarm switch you can simply disconnect the wire on it to see if the alarm no longer sounds.
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Old 09-05-2017, 07:58 PM   #8
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The only mechanic so far to look at it came back with 2 quotes,

1 quote to reman the engine @$6,000, quote attached.
1 quote for a new egine @ $14,760 installed, quote to big to attach but it's a Merc 383 MAG Engine for Bravo applications.

Just curious on your thoughts here on their pricing.


I took it out for ~35 minutes last night, and everything sounded fine, performed as it always has(for the few weeks I've had it) and no alarm sound at all. I have another mechanic coming out tonight for a 2nd opinion.
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Old 09-05-2017, 09:08 PM   #9
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When you took it out did you get her on plane? Did the oil pressure gauge read normal?

Is the first quote to reman your engine or install a reman one? If used in salt water buy a reman instead of using yours. The casting are loosing material to corrosion where a reman unit it an auto rebuilt to marine specs. Dies the $6K include install?

The 383 is a high price does it include install?

Either way it's your decision on what you want and pay for.
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Old 09-07-2017, 03:58 PM   #10
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Quote:
Originally Posted by mmwjr View Post
When you took it out did you get her on plane? Did the oil pressure gauge read normal?

Is the first quote to reman your engine or install a reman one? If used in salt water buy a reman instead of using yours. The casting are loosing material to corrosion where a reman unit it an auto rebuilt to marine specs. Dies the $6K include install?

The 383 is a high price does it include install?

Either way it's your decision on what you want and pay for.
Ahhh finally got the mechanic on the phone today and his mechanical gauge was reading 16-20psi at idle... This has been the norm of the boat since we had it so now I'm really thinking it's the sensor vs anything mechanical.

I did notice 1 of the riser's is significantly warmer than the other so they may need to be replaced soon.
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