jimishooch

i have a 1998 scarab 33 AVS w/ hp 500 carbs.
it has developed a hard alarm on the starboard ignition just turning the key one click right (hard alarm with no engine running) and stays on with the engine running. this is not the normal start-up alarm.
the depth gauge is on the port ignition.
all gauges read normal, all fluid levels are good including drive and the boat runs great.
most sensors have been tested (unplugged) and the alarm continues.
i'm beginning to think that this isn't even related to the engine.
any thoughts?
thanx
jim

Griff

On carbed engines, the alarm is hooked up 3 things.

Drive lube bottle
Oil pressure
Water temp

The wires going to the alarm sensors are tan with a blue stripe.

jimishooch

the sensors have been checked and double checked. what bugs me is the hard alarm is sounding without the engine running, isn't that strange?
the engine has to be running for the sensors to be activated, correct?

SCARABJ

iTrader: (1)

no on my 33 avs it would buzz until it built more than 5 psi of oil pressure then would go off..

obnoxus

Nope,,, the oil pressure alarm will sound without the engine running.

You will get the initial alarm,,, silence,,,, then oil pressure alarm will go on until you start the engine and it sees pressure then it will shut off.

Keep in mind there are 2 sensors for oil pressure.

One for the guage, one for the alarm

jimishooch

am reading 60 psi on the oil pressure gauge. all gauges are reading normal. keep 'em coming.........
the hard alarm comes on immediately when i turn the key one click right, no intial alarm or silence, comes on straight away.
thanx so far guys
jim

Griff

The readings on the guages don't matter. The sender for the oil pressure alarm is different than the sender for the guage as the sender for the high temp alarm is different from the guage sender. The alarm senders use a tan wire with blue stripe.

It can only be one of the 3 I listed. Unplug each sender one at a time. The alarm will not activate if they are unplugged. If the alarm is still going off, then one of the wires from one of the senders is grounding out.

I actually had two wires that were spliced together to one of my drive bottles pull apart last year. The bare wire was touching the engine and setting off the alarm.

jimishooch

ok, here goes, found three sensors with the tan & blue stripe wire. one was on the drive bottle, 2nd on left side of the t-stat housing and the 3rd on top of the intake manifold close to the t-stat housing on the right side.
for the life of us we could not find an oil pressure alarm sensor. please let me know where this sensor is, this is a 10 year old hp 500 carb engine.
pulling the sensors did not stop the hard alarm. if there isn't an oil pressure alarm sensor then i'm looking at a sensor harness short.
let me know
thanx
jim

Tinkerer

It should be down next to where the oil filter would go on a car. RH side lower corner of block

jimishooch

that oil pressure switch was hard to find, i pulled the plug and the alarm stopped. have new switch on order hopefully that will take care of the problem.
if i hadn't seen an hp500 carb on the stand at full throttle marine i wouldn't of known where to look for the switch. it was on the port side (as the engine sits in the boat) down and back tucked up underneath.
thanks guys
jim