Oil pressure issue
 

Just wondering if any of you guys have dealt with this and might save me some time.

but I'm having an issue that im 90% sure is being caused by either a bad sender or bad gauge.

The boat will have abotu 40-50 psi of oil pressure on both engines when just cruising 3400rpm or so... once i hammer down and get to above 4k i get one engine with a real bouncy oil pressure. I'm talking from 40to 20 back and forth almost sometimes. It is real bouncy where it seems like a gauge or sender. As soon as i shut down its fine at about 30psi hot. I can stay on plan for 45 minutes at 3500 rpm and not have an issue.

It started doing it out of no where towards the end of the season and I never got a chance to put a mechanical gauge on it. I did swap oil filter and even cut it open and it looked just fine.

You could switch the sending unit wires at the gauge if the problem follows its not the gauge. Put that back and then switch the sending units if the problem stay with the sending unit thats the problem. If it stays with the motor you may have oil problems. From what you describe sounds like a sending unit. Hard to test now that winter is here haha

I have that exact same bouncing problem with one of my volt gauges it bounces like crazy sometimes! I'm pretty sure it's the gauge! All new batteries and alternators!! It's a 84 with original gauges

Haider .... check the connector on the sender .....its the push on type and is vibrating at higher rpms ....its on the block @ the oil filter pad .....

I agree, if its bouncing around then its probably a wiring issue. I had issue with mine reading high when hot and low when cold. Turns out the Auto Meter pro comp marine guages don't like merc sending units, I put on a mechanical guage to be sure and yep, they read backwards. My only issue is the sending units are impossible to get to as there on the side of the block, so I bought factor guages that I'm going to put back in.

On a side note I am having a issue with my starboard tach, It's acting like your oil pressure guage. Its fine up to 1500 rpm's after that it goes haywire and bouces all over the place, but mellows out after 3k and runs fine after that. Junk guages.

Yea i was pretty positive it was a wiring issue.. wasn't to worried about it but still want it fixed.

Always to the rescue mike! I have the boat in a heated building down the street so I will have... months.. and months to work on it :)

I think I would go to mechanical Gauges .....unless you just need to realize that the electric just pretty much show that you HAVE pressure .....not how accurate it is ....My Fuel Pressure Gauges are about 10-20% shy ..... I can log FP on the Holley EFI and its pretty much dead on @ 48-50lbs ....m

I would temporarily rig a mechanical oil pressure gauge to see what's going on with the internals. I had this exact same problem years ago with my 311. Turned out that the pick-up tube had broken off the oil pump and would be fine when cool or cruising, but would be all over the place when warm and rocking it.

Don't just assume it's the sending unit or the gague. The problem you describe could easly be a oil supply problem. Like RedDog said it could be a pick up issue, also, it's not uncommon for a motor to pump too much oil up top and empty the pan when running higher RPM's for an extended period of time. It's why restrictors are put in passages. Put a mechanical gague on it and know for sure.

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i had a similar issue i thought was electrical....changed sending units even went as far a running a new wire from the sender to the gauge.....my engine builder told me to add oil to the very full mark on the dipstick....and it all went away...he felt the pan was getting sucked almost dry and the oil wasn't returning back fast enough...so i keep all my marine engines at the very full mark now :)

if you want to add the mech gauge, the oil pressure alarm sender is mounted at the top of the block on the rear of the motor .....right below the Distributor near the PS cooler ....you could add a T there and keep the alarm and add the Gauge ... I did that on my 311 and just mounted the gauge under the hatch .....m

1/8 pipe thread .....

I thought about that.. never had the issue before but I will look into it.

Yea im gonna hook a manual gauge and run the boat and see how far its off. I'm gonna do that soon incase i need to rebuild

Seems like that would pretty hard to monitor at 70 mph ... :)

:D


Well the issue I was having was the pressure would go to almost zero with Hot Oil at Idle .....So I could just crack the Hatch and check ..... it was actually about 20lbs when the electric gauge would be at zero ..... I have just put it on the rear seat to check while running .... :cool:

Check for loose belt as well

Loose serp. belt?

I've heard that a common problem in those year fastechs is that all the pink in the graphics and interior make for a loose nut behind the wheel!! Sr1's have more fun!!!




J/K!!!!

Get off the computer and come show me how to buff my boat!

Well... I sent the gauge and sender out to Gaffrig and they both checked out. That being said I was told that the sending unit looks old, corroded and might have some stuff on the threads giving it a ground issue at higher RPM.

I just hope its nothing in the internal engine

Haider .. I've pretty much concluded that those Gauges show that you have oil pressure ...Accuracy is a different story ....if your still using the push on connector it compounds the issue ....Did you ask Mark (Gaffrig) if they have a sender that has a ground terminal? All the new EFI senders have 2 wires Gnd/signal ... Or just go to mechanical Gauges ...m

All Gaffrig did was recommend a new over priced sender. I'll give it a shot and hope it fixes the issue

Haider ... As I had told you, after I replaced the connectors on the Senders it seemed to correct the issue but now the Starboard Gauge has started the fluctuation issue while underway ...I swapped the senders and the problem stayed with the Starboard Gauge...So I guess the gauges can be the issue as well ....Are yours the original OP Gauges that have the Low OP Light? I dont think they make those any longer ......m

Sender fixed the issue. Load off my mind