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OT Boat engine trouble shooting

D

David G

Well-known Member
I started thinking about the boat tonight, think it is an oil pressure shutdown.

The boat has a sender, which goes to the computer, and a switch which goes to an external shutdown module. I went out tonight and cranked it over. The engine fired right off, but killed about a second after that. The gauge is can bus, I did not see any pressure show up on that. I do not know if it is just too much delay or if there is no oil pressure.

The engine is a 5 liter (305) chevy with around 100 hours on it, I could not believe that the engine would really not have a complete oil pressure failure instantly. It has port injection, but a distributor, so would assume the oil pump drive is below that.

My first thought is to jumper out the switch and see if I can get pressure within a couple of seconds on the gauge.

Ideas are welcomed.
 
Yes, easiest and surest way to know.

What year is the engine? Are those still being made?

I recall 20+ years ago going into a Mercruiser/Chevrolet 305 engine. The engine was made in Mexico, really bad casting clean up. Lots of nasty edges that were never cleaned up, iron chunks in the pan... If that's what you have, good chance something found it's way into the oil pump.

Hopefully not, just an ancient recollection.
 
Does not matter if it is electrical or mechanical simply unhook the line/sending unit and spin it over. You should get oil out of the hole is the oil pump is doing something. A lot of the low oil pressure things would shut down an engine if the PSI was under 15psi
 
Does it have a safety switch with a lanyard that the driver attaches to the wrist?. If the switch for the lanyard is tripped it will start and immediately shut down. Don't ask how I remembered as I was being towed back to the marina. DUH...
 
Using a dead distributor from the junk yard, take the cam driven gear off and stick it in the hole drive the rotor shaft with a drill (in the direction of rotation, and pump oil Jim
 
Don't know what black box brains this boat has but a prior GM port injected V-6 (in a car) had a sender with an OP sender ( for the dash gauges) and a switch (on-off) both built into the screw-in unit. The on-off switch output went to the computer. The black box firmware had a wait time of a few sec before it tested that on-off switch for an ON condition - that is, a few sec for OP to build. If it didn't see that switch close after that amount of time, the box killed the engine (shut off fuel pump, if I remember correctly), presumably to keep down the chance of damage from no/too-low OP. Took me quite awhile to figure that one out, took hours in wiring diagram & other details in the original GM full-up shop manual. Hope this helps.
 
My first thought.

I never have had a reason to explore it recently, but the mid '80s Buicks and Oldsmobiles, at least the ones with a 3.0 V6 engine, were programmed to shut off the fuel pump if oil pressure didn't develop within about five seconds. I found that out the hard way when I'd rebuilt the engine on one and didn't get the wire to the oil pressure sender snapped on properly.

I have a huge 1/2" electric drill that will spin a fresh V6 engine, among others, on an engine stand with the spark plugs removed so I'd checked that engine for oil pressure while it was still on the engine stand and knew it had to be wiring when the engine would fire and shut off.
 
GM OBD I systems use a fuel pump relay to keep the fuel flowing until the engine tells the computer it has oil pressure. If no oil pressure, the relay times out and the fuel pump stops. If that relay fails, the engine won't start or it'll only run for a few seconds. If it's a throttle-body injected engine, check the fuel pump relay in the fuse panel/power center.
 
Exactly. Or, that on/off switch in the OP unit can fail while the OP gauge sender side of that unit is still ok. Turn key to start, engine starts, dash OP gauge goes high, engine dies. That's what took awhile to figure out.
 
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