Water through fuel pump - Help! (Pics)

[Joe_the_boatman]

1985 Merc 60hp. Compression's 100/110/110

While changing the fuel pump diaphragm and gaskets, I noticed water came out of the hoses going to the crankcase. At the time, I dismissed it as a fluke and reassembled. Lake test allowed us to run up to WOT for about 30 seconds, then would only idle us back to the ramp.

Had no water in crankcase-to-fuel pump lines today (after sitting overnight). Blew out w/ compressed air. Started motor in a bucket of water, ran 60 sec, and about 1/2 gal water came out the lower hose.

So, water drains out after sitting, which is good, but it fills up when it runs. Any ideas on what I need to look at next?

 

[Laddies]

Re: Water in crankcase - now what do I do?

Re: Water in crankcase - now what do I do?

The fuel pump on your engine is water cooled so you should be getting water out of the 2 hoses that are held to the pump housing with clamps.

 

[Joe_the_boatman]

Re: Water in crankcase - now what do I do?

Re: Water in crankcase - now what do I do?

Well, that's reassuring. I was going by the shop manual. Is it wrong? (the manual's for multiple years & models)

How does it work using water? It would have to pulse back and forth through there - there are 2 check valves in the pump.

I'm pulling my hair out (what's left of it) trying to get this thing running right.

 

[Joe_the_boatman]

Re: Water in crankcase - now what do I do?

Re: Water in crankcase - now what do I do?

Well, something's not right. I don't think there's supposed to be water flowing through there.

While idling, the lower crankcase tube gives a straight stream of water, no pulsing. Upper crankcase tube has air pulses in it. Water flows out of the pump when the upper crankcase tube is detached.

i checked the diaphragm that was replaced, and the diaphragm and seat side is attached to the crankcase hoses. Fuel side has the inlet/discharge discs. So, it matches the diagram from my manual, except for the water part.

Again, this thing runs great to 1500 RPM, but cannot sustain anything above that for a long period. It just runs out of gas.

I'm guessing I'll need to pull the exhaust cover off and see what's going on. This ever happen to anyone else? Anything else I should check first?

 

[Laddies]

Re: Water through fuel pump - Help! (Pics)

I really should not be wasting the time uploading this but you seem to like pictures, here is one right out of a Mercury Service Manual, I would not know how the pump works after 50 years repairing outboards but a picture might satisfy you.

 

[Joe_the_boatman]

Re: Water through fuel pump - Help! (Pics)

Laddies, don't be so grumpy. Sorry for doubting you. You're not wasting your time, you're helping me out here, and for that I'm grateful. You help out a lot of folks here and I'm glad you read my thread.

Looks like I need a better shop manual. I still don't understand the role of a constant stream of water on a displacement pump (and, I'm a mechanical engineer), but for now, it looks like it's right.

I still have a fuel delivery problem. Runs fine at idle, and idling in gear (indefinitely... had it run 30+ minutes idling in gear in the driveway). On multiple runs at the lake, it'll run at WOT perfectly (5200 RPM) for 30-90 sec, then runs out of gas. Seems only to get enough fuel to sustain 1500 RPM's or less from then on. Primer bulb stays hard the whole time.

I've replaced the fuel pump diaphragm, both carb inlet needle valves and seats and all carb gaskets. I added the 2 "bowl vent jets" that were missing.

I've disassembled and "dunked" the carbs, thoroughly cleaned them, reset floats to 11/16", and have done a "link-n-sync". Any turn of the mixture screws and idle goes down - they're dead on after the 'sync. Timing's 4?BTDC at 800 RPM. Idles in gear at 800-850 RPM, neutral idle is 1100 (a little higher than I'd like, but that's as low as I can get it when in gear).

I've removed all fuel lines and blown out w/ compressed air (all were clean). Primer bulb check valve is working correctly. I'm running 5/16" hose from the tanks. Sound right? It looks to be the same diameter of the fuel hoses on the engine.

I've replaced the rectifier, which fixed my tach and charging problem. Water impeller replaced last year.

My manual says 2psi on the outlet of the fuel pump. Does that sound right? I am going to test that next. Seriously running out of ideas here....

I've rebuilt 4 motorcycles from the ground up, pulled engines and transmissions, and I haven't taken a car (or any other engine) to a shop in 10+ years. Looks like I'll need another set of eyes on this one, unless someone has an idea I haven't thought of.......

 

[Joe_the_boatman]

Re: Water through fuel pump - Help! (Pics)

Fuel pressure at fuel pump outlet is 3.5psi @ 1100 RPM

 

[Joe_the_boatman]

Re: Water through fuel pump - Help! (Pics)

bump