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Old 06-22-2015, 02:57 AM
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Bubbacuse77 Bubbacuse77 is offline
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Oil warning horn

Gents, thank you in advance. I just purchased a 2002 197 that was not cared for nearly as well as it should have been but I got it for a great price. I am not new to inboards however Just new to Mastercraft and I am a handy guy so I plan to go over the boat and trailer to restore everything.

Well the first thing I need to figure out is why when the boat sits in idle for more than a minute or two the oil pressure will drop to zero and it will sound the alarm. I can shut the boat off turn it right back on and the oil pressure reads about 5 psi in idle. It also reads normal indications of around 20-40 psi when not in idle. Both the engine and the tranny look to have good oil and topped off. So I am wondering if anyone else has had this issue or if someone might know the cause?
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Old 06-22-2015, 07:18 AM
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5psi is pretty low and a cause for the alarm to go off. Typically caused by a tired engine where bearing clearances are worn. However, First step is to check it with a gauge to verify if an engine problem Or a sending unit problem. If pressure is fine testing with a gauge (~15psi at idle when warm) one of the senders is bad. Normally there is a sender for the guage ( this isn't connected to the buzzer/warning system) and a separate sender (really a on-off pressure switch) for low oil alarm (the first sends signal to guage and the second tells MEFI to turn on warning light and/or buzzer). IIRC this is how yours is designed but will have to check my MEFI literature later today to verify- maybe others can confirm? The alarm can also be triggered by water temp which has a similar set up so could potentially be a cause if everything else is OK.

Remember oil pressure will be lower when oil gets warm so if pressure is low when cold, it will only keep dropping until everything is warmed up. As an FYI, the pressure gauges aren't very accurate these years ours (2001) shows ~40 at idle and 70 when rpm is raised and jumps around quite a bit at idle.

Last edited by Rossterman; 06-22-2015 at 07:38 AM.
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Old 06-22-2015, 02:43 PM
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Maybe I should also do an oil change because I'm not sure the guy before me used the right weight of oil. For all I know he has 10w30 in it.
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Old 06-22-2015, 02:44 PM
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The engine only has 375 on it so I hope it isn't the bearings
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Old 06-22-2015, 09:04 PM
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Bump,,,,,

Anyone else seen this issue?
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Old 06-22-2015, 10:31 PM
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Its probably a sensor as these engines are pretty bulletproof. I have seen a number of posts on here where the low oil pressure sensor was plugged causing the alarm. It's a small hole and sometimes gets a piece of grit in it. This actually happened to me on a car once and I was able to remove the debris and it began working fine again. But, as I mentioned, until you check engine with a mechanical guage and determine if an engine issue or sensor issue, you are shooting in the dark. This is the logical next step (you could pull the sensor and see if it is plugged I suppose) However to help you out, here's potential causes for each:

Oil pressure measures low:
1. Worn main or rod bearings
2. Stuck oil pump bypass valve
3. Leaking oil galley plug
4. Wrong oil (10-30 won't cause this but 5-0 wt can cause lower readings)


Oil pressure,reads OK:
1. Bad low oil pressure switch
AND
2. Bad ground on guage pressure sensor or bad sensor (causing guage to read low)
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Old 06-22-2015, 10:54 PM
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I ordered a mechanical oil pressure gauge and the right oil to make sure. While I was at it I ordered new plugs and an impeller just to give it the once over

Thanks for the replys rostterman
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Old 06-23-2015, 01:29 AM
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Let us know what you find. Someone on here can probably give you the specs on what pressure range is at idle and 2k rpm from an indmar service manual to determine if you are within specs. Most non marine sites indicate anything below 8 psi at idle is a problem but most of those posting for the similar truck version of your engine that they see 20~35psi at idle.
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Old 06-23-2015, 11:48 AM
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Doing a little more research, check the oil filter adapter (aluminum part bolted to the block where oil filer screws on as a few have posted the bypass in that has been stuck with debris causing low oil reading. Also use a new high quality filter (not fram) as a few mentioned a bad filter caused similar results.
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Last edited by Rossterman; 06-23-2015 at 01:28 PM.
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  #10  
Old 06-24-2015, 02:02 AM
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I will defiantly let you know what I find out. With any luck I will get to it in the next couple days.

Thanks for finding that filter issue, I will look at that when changing the oil. I ordered a wix filter, I wouldn't put a fram filter on any vehicle.
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