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VancouverMark
04-22-2011, 11:05 PM
This tends to come on once and awhile while the boat is in gear or idle at low speeds. The motor has full oil, but the oil pressure gauge bounces around a little. When the alarm comes on, the motor shuts down. The I wait 5 seconds and it fires right back up with no alarm and good pressure.

Any ideas???

silverghost
04-22-2011, 11:40 PM
This tends to come on once and awhile while the boat is in gear or idle at low speeds. The motor has full oil, but the oil pressure gauge bounces around a little. When the alarm comes on, the motor shuts down. The I wait 5 seconds and it fires right back up with no alarm and good pressure.

Any ideas???

The oil pressure sensors can get old and start to fail.
This could explain the pressure readings jumping around on your gauge.
They are basiclly a pressure bordon tube connected to a variable voltage resistor/ rheostat.
Check all your electrical connections on the oil gauge & it's pressure sender and replace the oil pressure sender.
They are very cheap.

Also~~~
If your engine's oil pan is over-filled sometimes the crank & rods will splash around and cause foaming which results in air entrained in the oil~~~and thus lower than normal presure & jumping around oil pressure readings.

Good Luck.

silverghost
04-23-2011, 12:01 AM
By the way~~~
The oil pressure sender usually is a 2" cylnder shaped unit with a rubber cover that is located on the engine's left lower rear side screwed into the oil gallery. It is usually located near the oil filter on the side of the block's crankcase on Chevy Big & Small block engines.
Over 40+ years I have replaced at least a dozen of these senders on my various boats..
I hope this is your only problem and not another issue like a stuck oil pump bypass unloader/ pressure relief valve.

VancouverMark
04-23-2011, 11:08 AM
Thanks for the advice, I am going to pick up a new sender this morning and see if I can swap it out. It is probably a real bugger to get to!
I think I need a Sierra Part # 18-5899

I have a 1989 454.

mrfixxall
04-23-2011, 06:28 PM
First make sure the engines are at the correct idle speeds..IN GEAR..It should tell you on the flame arrestor or a id tag on the valve cove

If it's the same engine you have been having problems with check the grounds..

VancouverMark
04-24-2011, 09:09 AM
I am changing out the pressure sending unit today, i cleaned and checked all the grounds yesterday. I also noticed that the oil temp on that motor creeped up to 250.

First thing, am I reading the right gauges...I have an '89 Z33, I have 2 temp gauges on EACH motor, I am guessing the far left(port) is oil temp and the other water temp? And then the same on the starboard motor...far left(port) oil and the other water? The are not marked. I have sensors with a wire hooked up on each of the remote oil filters

MOP
04-24-2011, 02:19 PM
You more than likely have the stock Merc temp sender, temp warning, oil pressure sender and oil warning. That is standard stuff on Merc harnesses. Seeing as you noticed the oil temp climbing it could be a cooler problem, maybe a hunk of impeller sitting in the end. Many times guys will do a pump job and forget to back flush the cooler, then they wonder why the temps are funky.

Phil

bigdawgchallenger
04-25-2011, 04:28 PM
Mark, How big are the oil coolers? Remember I had to replace mine? This was the first year of this engine/outdrive for the boat and the oil coolers and drive/engine couplers are undersized. Last year I replaced the couplers, this year the oil coolers.

The oil coolers I replaced were 2" by about 6" long not including the P/S cooler. The one for big blocks (454's, 502's, and 496's) are typicly 2" by about 16" to 18".

Mike

VancouverMark
04-25-2011, 09:09 PM
Mark, How big are the oil coolers? Remember I had to replace mine? This was the first year of this engine/outdrive for the boat and the oil coolers and drive/engine couplers are undersized. Last year I replaced the couplers, this year the oil coolers.

The oil coolers I replaced were 2" by about 6" long not including the P/S cooler. The one for big blocks (454's, 502's, and 496's) are typicly 2" by about 16" to 18".

Mike


Mike
Let me guess, the oil coolers are buried at the back of the engine and low? Any chance I can get back there?

bigdawgchallenger
04-27-2011, 12:02 AM
it depends on the type, if they are the small ones, look on the port side of the port engine, down low. if they are the large ones, they should be behind the distributor, extends from head to head above bell housing . the starbord engine will be difficult to see.