Low oil pressure / Will not idle low

[ejbj]

Hi, i would like to thank the forum members for the valuable information i have found several times.
I purchased a new to me 88 Searay 230 cubby a few months ago. I have been working on it and giving it trial runs. First trial, i started sinking.. (thats another story, but.. i was smart enough to keep it on the trailer)
The boat has been neglected and i have been dealing with one problem at a time.
My latest problem was low oil pressure (i know its a big one). I had 25psi at start and on plane hot _3krpm_ it would drop to around 15, idle hot was on the high end of the red (10). My gauge has no numbers, I'm assuming it is 0-80. I thought maybe prev owner installed an automotive sender, but tested it and it was sending 243ohms with engine off, i still ordered one but don't thinks that is the problem.
Since the motor oil was very clean i had not changed it. Yesterday I replaced it with Mobil 1 15w-50 and also a quality filter (had to puncture the old one to take it out, it was crushed by the filter band wrench and it would not budge)
I added 5qts of oil and a 0.5qts of lucas stabilizer Goo, now my dipstick says that I'm way overfilled.
I went out and my pressure had improved significantly. 40 on plane, 20 hot idle.
The motor would not hold and idle, i had to rise it (1000) and readjust the throttle cable to match. I was unable to let gear off once engaged due to high rpm. Microswitch would engage if i force it, but engine would die in the process
The question are
1. Could there be any connection between the bad idle (that was good before and nothing else changed) and the oil change?
2. Did i overfill the oil?? (no pressure drop or foam) The dip says I'm about 2 in over.
3. How can i find the right dipstick for my motor. It has no mercruiser tag near starter and i have only been able to pull 57LG-SGI from the block.

 

[Fun Times]

It has no mercruiser tag near starter and i have only been able to pull 57LG-SGI from the block.

I don't see LG but to try and help id the engine better, Have a look in the area shown for your engine model size for GM's engine code letters, MerCruiser GM Engine Identification - boatfix.com

Or is that where (the area) you found the LG ?

 

[Scott Danforth]

if your 2" over, your over-filled period.

the dipstick wont show any foaming from the crank being submerged in the oil.

drain the oil to the proper level

1000 RPM is 350 RPM too high. idle speed is 650 RPM for a reason. its so you can get it in and out of gear.

 

[ejbj]

Fun Times; i took that number from the block, near the distributor/oil pressure port en the bell housing.
Using your link i was able to find the pad where the serial should be, but it seems to have gone beyond recognition. i tried flashing light from different angles and cleaned it with "blaster" and with a tooth brush (..sorry honey, will get you a new one :yield:..)
Scott; i put in 5.25Qts after draining from the plug and changing the filter. I am not positive what engine i have, but all 5.7 from the era seem to take 5 or 5.5qt. My guess is that the dipstick is not the correct one. I also had to bend the dipstick a bit because it would jam and not go in. When i purchased the boat the dipstick was not in the "hole" but laying on top of the engine.

Thanks!

 

[ejbj]

After much diagnosing the problem with the bad idle, i realized the engine would run better with choke so i started looking for vac leaks or fuel starvation. One of the primary venturi had visible gas pulverizing, the other didn't. So i ordered a kit and result the carburetor (rochester quad) There was some gunk in it. All is good now.
Carb is automotive, but from the same time period as the engine, i wonder if PO replaced it or if this was stock (Rochester 17056207 R4-M4MC)
Now with the air mix at best and the idle screw all out, barely touching its spring, Engine Idles smooth at 620-640rpm. I replaced the Oil sender since mine had a "dirty track" and would jump to zero at 40psi. I opted for VDO 3360-801 240-33ohm 0-80. Also installed a kit from Sierra with a 6psi oil switch, a 200F switch and a buzzer. If i kill the engine from the engine itself, it takes a good 3-4 seconds for oil pressure to drop below 6psi and the buzzer to go.
I still need to get the proper oil dip stick.. i will probably have to measure level with 5.5Qts In, and find one with the full at that length, unless someone has a better idea.