4-Beep Oil(?) Alarm

**Basnova** · 07-25-2025, 11:03 PM

Ever since I've had my 1998 Promax 300 on my bass boat, which I bought new, every once in a long while, after towing a couple of hours to a lake, upon startup I'd get the 4 beeps, even though it would initially smoke like hell, as usual. The beeping, and smoke, would go away shortly. I attributed it over the years to the engine being tilted up and bouncing all over the road back from a trip, sitting in my garage for a few weeks, then bouncing around again to another lake. It would go many trips without beeping, sometimes years.

3 trips ago, it beeped upon startup. After a couple of runs the beeping stopped, as has been common.

Before the next trip, I topped up the oil in my 2 gallon reserve tank, even though it was already a little over half full. Looked at the engine-mounted reservoir, and it was 2" or so from full, as it's always been. Looked at the 1/4" clear hose at bottom of engine-mounted tank and it's full with no bubbles. No beeping at all on that trip, not even on startup. Boat run was quite short and easy, to the tune of about 12 gallons of gas the entire day, because we were on fish from the very first stop.

This past Wednesday, after driving over a couple of hours to a lake, it beeped upon startup. Smoked like hell, as usual. Even after turning it off and back on several times, it beeped on a 12 mile run. 6 hours later, on the 12 mile run back, it beeped. Took the engine cover off, looked at everything again, and all looked fine.

Could it be the sensor? If so, how do I test that it? Anything else I should look for?

Thank you.

**skialot2** · 07-26-2025, 01:00 AM

99% sure the onboard oil tank is supposed to be full. Not 2" from the top. The oil warning for that is 4 beeps every few minutes.

**David - WI** · 07-26-2025, 02:42 AM

Full... like up into the neck of the tank.

**Basnova** · 07-26-2025, 05:34 AM

Thank you guys for responding so quickly. So, do I just remove the engine-mounted tank cap and fill it there?

Also, will the system beep if the motor is not running and that tank is low, or does the motor have to be running? I am asking so I know what to do to see if the beeping stops after filling that tank.

**XstreamVking** · 07-26-2025, 07:36 AM

Pull the cap on the engine tank, run the engine. if it fills up then replace cap. If it won't fill fairly quickly, the check valve on the air pressure hose (star lower part of the engine) is bad.

**Basnova** · 07-26-2025, 10:12 AM

Originally Posted by XstreamVking

Pull the cap on the engine tank, run the engine. if it fills up then replace cap. If it won't fill fairly quickly, the check valve on the air pressure hose (star lower part of the engine) is bad.

Just so I am clear:

Because of what I described, and the fact that the engine tank has pretty much always been 2" low, it's possible that I might just need to bleed it, correct? I assume the procedure you describe is how to bleed the system, so when you said if it starts to fill up, "replace" the cap, you meant to simply put it back on, not get a new one, correct?

Also, I was actually wondering if there was a filter or something that might need looking at, but since the engine tank has oil that means nothing must be blocking the oil path from the remote tank clogged, right?

Thank you.

**David - WI** · 07-26-2025, 10:20 AM

Yes, just put the cap back on (securely so it doesn't leak under pressure).

It should beep with the key "on" but engine "off" if the tank is low... also there is a "buffer" (timer) built into the system so it will take maybe a minute or two after the tank goes low or you turn the key on with the tank low, for the buzzer to actually go off.

**XstreamVking** · 07-26-2025, 10:57 AM

Also, the excessive smoking at start-up could be oil in the boats main tank getting pushed back into the engine by the residual air pressure and a non functioning check valve after shut down. The valves clog and fail often since they lie at the bottom of the crankcase. Easy fix.

**Basnova** · 07-26-2025, 11:16 AM

You have all been so helpful in helping me understand how the system works, and providing such informative insight. Thank you for that.

I forgot to mention this, but when I said I inspected the engine tank level, I looked at it with the engine off. My question here is, should the level in the engine tank be the same whether on our off? If, when I go try the bleed procedure, it fills quickly and is full when running, but the level drops when off, is that indicative of a problem or is that normal? I would think, based on the info you've all provided, the level should always be full, but just thought I'd ask, to be sure.

Also, during my inspection, i noticed the engine tank cap is on so tight I'm thinking i might end up needing to use channel locks to unscrew it. Of course, I will try wearing rubber gloves first. Or, do any of you have any tips in this regard?

**skialot2** · 07-26-2025, 11:31 AM

You should be able to bleed the tank by just loosening the cap. It takes about a minute to build pressure in the remote tank before the on board tank will fill up. If the level drops after you shut it off, you have a leak.

**David - WI** · 07-26-2025, 11:59 AM

It should stay full.

Somebody tightened the one on my brother-in-law's boat so tight that it cracked the tank up by the filler neck... so the tank would leak down to the crack below the neck and he had oil leaking down the sides of the intake.

**Basnova** · 07-26-2025, 12:25 PM

Originally Posted by skialot2

You should be able to bleed the tank by just loosening the cap. It takes about a minute to build pressure in the remote tank before the on board tank will fill up. If the level drops after you shut it off, you have a leak.

I remember at the dealership when I bought it in 1998 that they said not to touch the engine tank cap because it needs to be tight and you don't want to tear the gasket. When you fill oil, fill the remote tank. So, that's what I've done over the years. I had it professionally serving e for many years, but sure if they ever loosened that cap. So, I am very concerned about loosing it if it hasn't been opened in all these years, and that it's so tight I might ruin the gasket. If that happens where do I get a replacement gasket? No one wants to service my engine near me, and parts seem to be far and few between out here. Can I make a gasket out of something, if need be? Of course, all this is moot until I look at it today or tomorrow.

**Basnova** · 07-26-2025, 12:28 PM

Originally Posted by XstreamVking

Also, the excessive smoking at start-up could be oil in the boats main tank getting pushed back into the engine by the residual air pressure and a non functioning check valve after shut down. The valves clog and fail often since they lie at the bottom of the crankcase. Easy fix.

Where do you get those? Parts for this motor are hard to find local to me. Will look at motor today or tomorrow, but is it a simple thread out, thread in?

**Basnova** · 07-26-2025, 12:29 PM

Originally Posted by David - WI

It should stay full.

Somebody tightened the one on my brother-in-law's boat so tight that it cracked the tank up by the filler neck... so the tank would leak down to the crack below the neck and he had oil leaking down the sides of the intake.

Thankfully, it doesn'took like that's the issue for me, but I will be careful with that tank and cap.

**XstreamVking** · 07-26-2025, 12:45 PM

Most merc dealers will have them. Boats . net is also a good place to look parts up online. Just look by serial number and part type. I think you may need part # 7 off this diagram. https://www.boats.net/catalog/mercur...ck-and-end-cap CHECK VALVE
Part #432783 is what I come up with. 33 bucks or so But do a search with your serial number and double check. Pull yours and try and blow back thru it. It should only go one way.