Gas in oil on Crusader 350, model 270

I have a 1989 Trojan 321 Sedan with gas in the oil. A little history about boat. Boat sat wrapped for 3 years with 180 gallons of bad fuel. Pumped out fuel and put 2 large bottles of Seafoam into each tank prior to filling with new marine gas. Rebult carbs in July 2014. Changed fuel filters on both engines.

Problems:

1. Gas in oil. Both engines. (I can lite the oil on fire)
2. Port engine wouldn't initially go over 1800 rpms until I changed out plugs. Then it ran great for awhile but then experienced the same issue. All plugs removed and are free of oil and just have black soot on them.
3. No problems with the Starboard engine other than gas in the oil.

Boat sat for 3 years. Could the fuel pumps be bad? Carb float issues? Anti-siphon valves?

Where should I go first with these problems?

Did you have the original carbs rebuilt or did you obtained already rebuilt carbs that replaced the original ones?

what condition are the engines in; ie leakdown test results?

Last time both engines received a complete (comprehensive) tuneup?

The carbs are the original Rochesters but rebuilt in July. Engines have 320 hours each and run fine at idle. But when you run them up under load the Port won't go over 1800 rpms. I have changed out plugs, wires, caps and coils.

Leakdown not done.

The boat had bad fuel in the tanks, which was removed. Could carb float be sticking? Or bad fuel pump?

if the engines "run fine at idle", its a good indicator they are not flooding....try getting a whiff of the exhaust to see if it is running rich...

If the fuel pump diaphragm ruptures, the fuel dump path is into the primary bore of the carb...again, you should be able to detect this with your nose and then verify it with your eyes.

Some will tell you the rochesters will leak fuel from the bottom of the casting...if they are the original q-jets, they have the superior factory sealing system...rochester figured it out pretty quick and eliminated the issue...

If you have rebuilt the ignition system, you also need to verify the timing advance is correct...the OEM distributors were plagued with advance mechanisms that didn't stand up very well to marine use...

If the timing curve is correct, I'd bet the carbs aren't completely dialed in and the engines have been spending a lot of time idling...pretty common

Thank you.....great information. I'm suspecting the fuel pump diaphragms are ruptured due to sitting for so long. Changing them both out tomorrow.

They may be ruptured but I'd be incline to verify it before unloading the cash on new fuel pumps....

And if you replace the pumps, make sure they are marine rated...

BTW, you'll be likely to need new tygon tube (the "sight tubes") going back up to the carbs...if it is rigid & brown, it has deteriorated.

Leaking mechanical fuel pump diaphragm?

Jeff

Magus Three Six

I have had gas in the oil for as long as I can remember. 1989(?) Baylinersingle 305 Quadra Jet. And then in the (2)Crusader 270s Quadra Jet on my 42’ houseboat. IMHO there is only one fix: Purchase a new carburetor(s).

I fought withthe Bayliner and then the houseboat for a total of 8 years and was DONE messing around. The carbs were pouring gas into the intake manifold! Complete rebuild of carbs, frequent oil changes, spark plugs (16 at atime every month on the houseboat), black soot, and poor performance andidling. I won’t even consider the amount of money I spent.

Two years ago Ipurchased (2) new Edelbrock marine carbs. I paid just short of $400 for each including the adapter plates. OH THE JOY. Just last month I replaced my first set of spark plugs. That’s almost TWO SEASONS! No more gas in the oils.

And best yet....1.6MPG (approx, hey I know this is a boat!) 42’ Gibson houseboat, 15 people on board,generator running, 50 mile round trip at 9 knots. WOW

Magus Three Six said:

1... The carbs are the original Rochesters but rebuilt in July. Engines have 320 hours each and run fine at idle.


2.... But when you run them up under load the Port won't go over 1800 rpms. I have changed out plugs, wires, caps and coils.


3.... Could carb float be sticking? Or bad fuel pump?

Click to expand...

1... After shut down, look into the primary bores for fuel leaking onto the intake manifold planes. If the carburetor is leaking fuel from the float bowl, it will show up there.

2... See Kim's response below.

3... Possibly leaking from the carburetor body, or from a ruptured fuel pump diaphram.

kimcrwbr1 said:

Map the curve on both distributors and compare results.

Click to expand...

Ditto Kim on this one.
If you are still using the OEM ignition systems, these are likely mechanical advancing units.
Flyweights and flyweight return springs can become compromised due to rust and/or corrosion.


Mark off your harmonic balancers up to approx 35* to the advance side of the OEM TDC marking.
Strobe the markings as you run through an rpm range from idle up to 3,500 rpm.
Jot down the ignition advance in incriments of 250 rpm making this into a graph from.

Compare these readings to your OEM advance curve.


NOTE: the OEM advance curve will be minus BASE or Initial advance numbers in the vertical scale.
This means that you'll need to do the math when comparing to the actual the curve that you made into graph form.

Example Only:

Here's a Volvo Penta ignition advance curve.
The corresponding advance/RPM graph numbers do not include BASE or Initial advance.
But as you strobe your markings dynamically, BASE or Initial can't help but to be included in what you see.

Look at the 3.7K rpm value for the spark advance. You'll see only 22.5 degrees of advance being shown. Your engine won't perform on only 22.5* @ 3.7k rpm.
Now add BASE of let's say 8*.
Now at 3.7K rpm, the engine is seeing 30.5*..... perhaps a bit agressive without knowing the engine build, but you can see how this works.

On a side note, you may have a combination of issues. What kind of fuel was in the boat while it sat? Full of ethanol? It could have eaten fuel lines, gaskets, etc. Even though you put new clean fuel in, there could be other damage yet to show itself or contributes to the the troubleshooter process.

I think I read a recent article that the boating industry advocates to push for ethanol free marine fuel failed and the EPA will require ethanol in all fuel even marina fuel.