Bad fuel pump = engine flush with gas

[Bluto]

I have a 25' commercial boat with a Chrysler 360. It was my father's boat. The engine is about 20 years old. It rarely saw over 2000 rpms, had so-so maintenance. So it probably had some sludge.

Last fall the fuel pump went up. On a marine engine the fuel pump bypass dumps gas into the carb. I had it towed into the marina. I did not know the fuel pump went (and did not shut off the fuel line). I came back next weekend and the entire motor was flooded with gas (intake, cylinders, and crank case).

So basically my entire motor was flushed with gas through the carb.

I turned off the fuel, pulled the spark plugs and hand-turned the motor to clear the intake and cylinders. I then pumped out the crank gas/oil mixture. I replaced the fuel pump, added oil and a new oil filter.

I ran the motor maybe 3 minutes. The oil looked like dirty and thin, honey.

I changed the oil and filter again. I added crankcase stabilizer and ran for 5 minutes, fogged the motor, flushed the raw water system with RV antifreeze, etc. The oil looked OK. The motor was winterized.

I'm ready to put her back into the water. How many more times should I change the oil and how many hours? Should I consider Auto-Rx?

I was thinking:

1st oil and filter change at 10 minutes.
2nd change at 30 minutes(1st time at operating temp, evaporate any fuel remaining)
3rd after 1 more hour, then back to normal changes.

 

[Lead Shoes]

That would be A LOT of gas flooded into the engine, I'd say flush the engine or keep changing the oil after running it for 5 minutes until it looks right again..

 

[JHZR2]

Agreed. Since the goal first and foremost is to get viscosity up to offset the fuel, I'd be using cheapest 20w50 I could find. Recycled oil would be ok too if you know the source. The more the better.

 

[Chris142]

Any leftover gas should evaporate once it gets up to temp. I'd use it for the weekend or whatever then change it one more time and not worry about it from now on.

 

[BigCahuna]

If you solved the fuel problem and changed the oil twice, you should have the gas out of the motor. Getting the motor up to operating temp will burn off any remnants of gas left in the crankcase.Changing it more will just give you more oil to dispose of and not really any benefit.,,

 

[440Magnum]

I think you already solved the fuel incident. Given that this is a carbureted 360 and not the newer "Magnum" EFI engine with the lower intake plenum leak problem, I actually doubt there's much sludge in there even with "so-so" maintenance. If you want to be really safe, change it again after a few hours use (maybe a weekend's worth- I don't really know how you operate the boat- the objective is to get the oil fully hot before this change).

The carbureted LA engines were just about as bulletproof as any gas engine ever built by anyone anywhere. If there's any weakness there at all its leaking coolant into the oil when the timing cover, which also serves as the waterpump backing plate, corrodes. I'm not sure if that's even applicable on a marine engine, but it might be even more prone to it if its got raw-water cooling (is it truly a Chrysler Marine engine? I thought they were out of the marine biz more than 20 years ago, but I honestly don't remember).

 

[Bluto]

The fuel problem is taken care of. I will use gallons of Super-Tech 20W50 or 10W40 oil and Fram filters the first changes this season. There is no way to tell fuel dilution so I'll do at least 2 quick changes. Cheap insurance.

How would the fuel affect seals or gaskets? Would auto-rx or another additive be a good idea?

I will do regular oil analysis to look for problems.


I think the Chrysler 360 was available until 1991. I don't believe it is a true Chrysler Marine engine. The flame arrester has 'Chrysler 300 Series' on it. But the valve covers have 'Conversion by Indmar.' I'm guessing Indmar did some Chrysler conversion back in the 1990s (or Indmar dealers carried Chryslers). I have not found the engine ID plate yet. I need to get out a flashing and mirror

It has a anti-freeze cooling system (clean water) with a raw water heat exchanger. I plan to change the water pump this year. I'll take a good look for corrosion.

 

[Steve S]

Change the oil and you are good to go.

 

[440Magnum]

Originally Posted By: Bluto
The fuel problem is taken care of. I will use gallons of Super-Tech 20W50 or 10W40 oil and Fram filters the first changes this season. There is no way to tell fuel dilution so I'll do at least 2 quick changes. Cheap insurance.

How would the fuel affect seals or gaskets? Would auto-rx or another additive be a good idea?

I will do regular oil analysis to look for problems.


I think the Chrysler 360 was available until 1991. I don't believe it is a true Chrysler Marine engine. The flame arrester has 'Chrysler 300 Series' on it. But the valve covers have 'Conversion by Indmar.' I'm guessing Indmar did some Chrysler conversion back in the 1990s (or Indmar dealers carried Chryslers). I have not found the engine ID plate yet. I need to get out a flashing and mirror

It has a anti-freeze cooling system (clean water) with a raw water heat exchanger. I plan to change the water pump this year. I'll take a good look for corrosion.


I don't think the fuel should have hurt seals or gaskets too much.

Indmar conversion sounds about right. I think Chrysler themselves got out of the marine business before 1980.

FWIW, I'd use Fram ToughGard filters instead of orange cans on those first changes- you want a filter not likely to collapse, have internal leaks, or go into bypass mode if you're concerned about stuff breaking loose. Yes, its "throwing away money" on a filter meant to be there for a short change, but its also a change when you WANT the filter to absolutely positively do its job.