Help with engine stalling

[gpapich]

Hey guys,

I need some help. I have a 1976 Mercruiser 280 TRS setup. This means transmission and power trim.

My symptoms are that my engine stalls after I first start it and I begin lowering my outdrive (I can start the engine with the drive raised as the water pickup is hull-mounted. I use this procedure as it saves the load on the battery). I restart and it settles back into high idle (~2000 rpm) fine. I continue trying to lower the drive and it stalls.

The second piece to the puzzle is that my outdrive acts as if it might have some junk in the check valves as it hangs up when it drops into the underway trim adjustment range (out of the trailering range). Could this be electrical and causing the engine to stall? Lately, to get the drive all the way down, I've been backing away from the launch ramp and letting the forward thrust when I shift help the drive the rest of the way down.

The third thing is that the engine will stall when I attempt to shift. Sometimes it works, and sometimes it doesn't. I'm not sure if TRS's had shift interrupt microswitches like Alphas and Bravos. I haven't gotten back to the boat to start looking and troubleshooting and I don't have the Mercruiser manuals for the engine and tranny. Last weekend was the first time the boat was truly unreliable.

Could all of this be oil pressure related as in drop in rpm causing a momentary drop in oil pressure and enough to trigger the oil pressure sender and ignition safety interlock? (I'm not even sure I have such a set up, but going off of automotive knowledge)

Help me out please! We're still in Indian Summer out here in Northern CA and the Delta is too nice not to be out on the water.

[Formula Jr]

You have some truely weird stuff going on Here

Hey guys,
I need some help. I have a 1976 Mercruiser 280 TRS setup. This means transmission and power trim.


My symptoms are that my engine stalls after I first start it and I begin lowering my outdrive (I can start the engine with the drive raised as the water pickup is hull-mounted. I use this procedure as it saves the load on the battery). I restart and it settles back into high idle (~2000 rpm) fine. I continue trying to lower the drive and it stalls.

Does it stall, or does it just stop? There is a slight difference to the ear. A stall with go though one or two cylinder firings before the engine stops, meaning the elctrical side is working okay. It the engine "quits" as in an instant lose of all firing then something is turning off power to the coil. I think "Stall" may be the wrong word here. This description points to a short that is some how tied into your ignition, or that your battery is so weak it can't power both the ignition and the tilt.


The second piece to the puzzle is that my outdrive acts as if it might have some junk in the check valves as it hangs up when it drops into the underway trim adjustment range (out of the trailering range). Could this be electrical and causing the engine to stall?

Yes, I think this is your best lead. Your trim limit switch is activating a curcuit that is involved with the short.

Lately, to get the drive all the way down, I've been backing away from the launch ramp and letting the forward thrust when I shift help the drive the rest of the way down.


The third thing is that the engine will stall when I attempt to shift. Sometimes it works, and sometimes it doesn't. I'm not sure if TRS's had shift interrupt microswitches like Alphas and Bravos. I haven't gotten back to the boat to start looking and troubleshooting and I don't have the Mercruiser manuals for the engine and tranny. Last weekend was the first time the boat was truly unreliable.

Your boat doesn't have what you would call a shift interrupt switch like the alpha. Bravos don't have shift interrupt switches. TRS does have a neutral safety switch. And this is likely involved.


Could all of this be oil pressure related as in drop in rpm causing a momentary drop in oil pressure and enough to trigger the oil pressure sender and ignition safety interlock? (I'm not even sure I have such a set up, but going off of automotive knowledge)

No


Help me out please! We're still in Indian Summer out here in Northern CA and the Delta is too nice not to be out on the water.

test one,
Toss in a known good battery.

test two.
Replace neutral safety switch or by pass the old one JUST FOR TESTING.

test three.

Have a buddy check the voltage from the Battery to the the coil while you drop the drive down past the trim limit.

[Cuda]

As Poodle pointed out, don't start it with the drive up. My take on your problem is I think you have a weak battery, it may be the battery, a connection, or alternator. As far as the drive not lowering easily, it may need the drive rams rebuilt. Have someone push down on the drive while you try to lower it (not running of course), if it goes down easily, you probably need the cylinders of the ram rebuilt, or as Poodle pointed out, perhaps air. What's your idle speed? If it's too low, it may stall going into gear. My Trs lowers slow as hell, but I have tried pushing down on it, and it didn't make a difference, so I'll probably have to look at the pump, or the oil.

[gpapich]

I never thought of the battery/coil relationship. Also, it's definitely "quitting" as opposed to a stall. It seems electrical. All these are great ideas and something I need to check on a 30 year old boat. I think I have a bunch of things all going on that need attention.

Thanks again!

George

[MOP]

Start with the basics, clean all connections both ground and positive, once you are sure thats all good then go onto the other things. I have watched so many guys do the "Easter Egg" thing for days and finally find something simple that should have been found in the first hour or so.

Phil

[Formula Jr]

Phil is absolutely right. It does no good to go anywhere till you know you have clear connections to the circuits involved. That's why he's the 13. :)