92 150 BlackMax alarm at higher rpms

[ibmoe]

Hello all,

Newbee here, searching thru the archives but I haven't found too much.

I've got a 92 Mercury 150hp 'BlackMax' . Bought the boat from a friend last year. It sat for a few year before I got it.Changed the spark plugs, lower oil, 2 stroke oil, fuel, fuel filter and impeller last year. It was running great. Last weekend took it out and got an alarm, 2 beeps, while on plane. Stopped. Got up on plane again (~3500rpms/19kts) then it happened again. Stopped and started again and everytime the same thing. Checked the oil level and it was 1/2 a tank. Got towed in since I didn't want to damage anything. Anways, I just ordered the service manual from Merc as well as the Seloc manual.

Could this intermittent beep be a high temp alarm? If so, what should I check? Impeller has less than 50hrs on it.

Oh, FWIW, the oil reservoir on the motor was less than 1/2 way full (closer to 1/4empty) could this be causing the alarm? If so, is it a sensor, or a clog, or????

I've read about checking the thermostat, poppet valve and fuel/water separators, but can't find too much detail on where to check for these. Any help?

Lastly, since this occurs only at higher rpms, how can I test? I was told not to rev the motor while on the bunny ears.

 

[j_martin]

Re: 92 150 BlackMax alarm at higher rpms

The alarm system is working normally. The tank on the motor is supposed to be plumb full tight, to the point that if you crack the cap it should leak out instantly.

That tank is kept full by a presurized tank in the boat. It must have oil in it, and the lines to the motor must be in good shape. There is one that goes to a vacuum relief valve, then to the top tank. The other line goes to a check valve that feeds crankcase pressure to the boat tank. All that has to be in good shape.

The system is designed so that if the feed system fails, the alarm will sound, and it will give you about a half hour at WOT to get home. If you think the oiling is failing, you can transfer enough oil from the boat reservoir to the main fuel tank to make approximately 50:1 mix, (2.6 oz/gallon) then run back in, or even keep running for the day. The tow was unneeded expense.

The owners or service manual explains how to hook up the advanced oil system, and what to do if the alarm sounds.

hope it helps
John

 

[ibmoe]

Re: 92 150 BlackMax alarm at higher rpms

John,

Thanks for the info. I went back and checked the reserve tank on the motor yesterday and confirmed it was at 3/4 full. I checked all the oil lines and they all appear to be fine. The oil line going to the oil reserve on the motor has a T fitting and one part of the T has a hose attached that does not connect to anything. Is this the vacuum relief or crankcase valve?

On a side note, I confirmed that I do not have a fuel/water separator filter. I plan on purchasing a Mecury fuel/water separator filter and installing that as well as replacing the inline fuel filter.

 

[j_martin]

Re: 92 150 BlackMax alarm at higher rpms

That T thing is the relief. It is there so that if the oil line from the boat gets restricted. It would then allow a little air into the motor oil tank rather than have it cave in from the vacuum. The tail doesn't go anywhere, just guides any oil that leaks from the valve to the cowl pan.

If you idle it on the cuffs, then crack the top cap on the engine oil reservoir slightly, it should slowly fill up. Let it fill till it just starts to spill out the top, then tighten the cap real good and clean up the mess. You should be good to go.

If it doesn't fill, troubleshoot the check valve and lines to the boat tank.

I'd recommend using a 60 gpm racor fuel water seperator, genuine mercury gas line, and take out the bayonet connector on the motor and run the line direct to the oil injection T. At the very least, make sure the connectors are Mercury metal connectors, and not plastic aftermarket junk. This engine takes a lot of fuel at WOT, and will burn down in a few seconds if it's starved.

hope it helps
John

 

[gss036]

Re: 92 150 BlackMax alarm at higher rpms

Don't try to get the cap "real" tight, just tight enough so it doesn't leak, they have a bad habit of cracking at the top of the internal threads. Very commom complaint and while they are only $50, does get costly after a while.