Mercruiser 165 Stalling/dying Problems.

Good Evening,
I have a 1978 Glasply with a Mercruiser 165. The boat will start up and idle just fine. But sense buying this boat last year, I have had the same problem of this boat stalling out and dying anywhere from 25 to 125 minutes at cruising RPM. When it begins to die, the boat will sputter in RPMs (high to low) and then die. The boat will not start up right afterwards however if you give it a few minutes it will start back up and idle. If you try to bump the RPMs up the boat will sputter again and die. I just installed a perTronic ignition system, spark plugs are new. The cap, rotor, and spark plug wires are newish. I just replace the thermostat. Last fall I took the cover off the fuel tank, completely drain the tank, installed two new filters and have only ran non eth gas. During operation the boat stays in the middle of the green arc, once dies obviously rises to upper green ark lower yellow ark. (my temperature gauge is just in colors no numbers). Coil is warm to the touch definitely not hot by any means when the boat dies. Out drive was just serviced and impeller changed. I'm at a loss for what else to replace to fix this issue. I live on a lake were an inconsistent boat could get you into a lot of trouble. Serious wind and waves, extremely limited docking and lots of rocky cliffs. I've done some reading on the forms here about other similar issues, some have suggested putting a relay in the coil wire to ensure it's getting maximum volts. I replace the coil six months before installing this new ignition system? Maybe I need to install a new coil? I guess it's possible that one shorted out with the old point system? I would enjoy any advice to help fix this issue and get a reliable boat, if there is such a thing
Thanks!

I would enjoy any advice to help fix this issue and get a reliable boat, if there is such a thing

Click to expand...

Ayuh,..... The way it dies, sounds like a lack of fuel issue,.......

To diagnose it, When it dies, immediately check it for presence of Spark, 'n Fuel in the carb,......

One or the other, will not be there,......

Test run with portable fuel tank.

Upon some further testing this morning, I ran a multimeter on the top of the coil,
with the ignition on (got 4.5V) while the engine is running (got 1.12V). Anyone else have this issue or a way of fixing it?

Correction with the ignition on (got 5.5V) while the engine is running (got 12.58V).

When you cleaned the fuel tank, did you check the anti-siphon device? It should be located on top of the tank, immediately before the fuel line to the engine. They sometimes collect debris while running eventually causing the engine to die. Then, the returning fuel clears the debris enough to allow the engine to start.

Also, did you check the screen on the fuel pick-up tube way down in the bottom of the tank?

DJR said:

When you cleaned the fuel tank, did you check the anti-siphon device? It should be located on top of the tank, immediately before the fuel line to the engine. They sometimes collect debris while running eventually causing the engine to die. Then, the returning fuel clears the debris enough to allow the engine to start.

Also, did you check the screen on the fuel pick-up tube way down in the bottom of the tank?

Click to expand...

Yes the screen was cleaned i took a vacuum and paper towels and cleaned the entire bottom of the tank to shiny plastic. This was just a few months ago, only non ethanol since.

Another update, Took it out for a test drive today and after approximately 15 minutes at cruise (3k) rpm I bumped her up to 3500, shortly after it died. I installed an in-line fuel filter just before the water separator filter and it was bone dry right after it died.I hooked it up to a 5 gallon gas can shortly after and it started right up and ran like a top out to full throttle. Evidently, i did not get the entire tank cleaned and debris is getting stuck in the pick up tube. Ugh! what a headache. I've had the top off the fuel tanktwice already, both times to fix a leak, and it is an extreme pain to put on because it is heavily corroded and I end up using half a bottle of 3M 5200 to fill all the holes and create an airtight seal.... If anyone has any ideas other than take the top off the fuel tank and try to clean it again please let me know. Obviously there still is a large amount of debris in the front of the tank that I cannot reach. It is a plastic tank. Thanks.

Yes. Have the tank professionally cleaned. Ask at your local marina as these tend to be very small operations of one or two people.

and it is an extreme pain to put on because it is heavily corroded and I end up using half a bottle of 3M 5200 to fill all the holes and create an airtight seal....

Click to expand...

Ayuh,..... Sounds like the tank is Junk,........ Replace it,.....