Engine problem - '85 Mercruiser 170

[THEFERMANATOR]

Originally Posted by scook

Changed the fuel lines - did a careful job - only gentle bends. When I cut the 10 year old hose open, was surprised to find it in good shape - slit it in half, bent it both ways back onto itself - no cracks, loose rubber or anything like that.

Still the same problem - started great & ran great for about 20 minutes and RPM started dropping off. Turned around and headed back - as it started coughing and wanting to die, I pumped the throttle and got a little more out of it. That tells me it must be a fuel problem - right?

I put some air pressure on the fill tube and got nice air flow out of the vent, so I don't see how it could be bad venting causing a vacuum to build up in the tank.

Oil doesn't smell of gas so fuel pump not leaking into crank case but I can't think of anything it could be at this point but the fuel pump???

Before I order a fuel pump, is there anything I'm missing? Remembering back 10 years when I got the boat because it was doing exactly the same thing, I replaced both the fuel lines and the pump before running it and distance, so it could have been the problem then.

Found this pump for a lot less than other prices I've seen - anyone know anything about this supplier or the product? http://www.cpperformance.com/p-23396...-861676a1.aspx It made me a little nervous that for this mechanical pump, the product description said it had solid state electronics and a simple 2-wire connection.

You sure thats the right pump? It says it's for a 3.0L not a 3.7L. ust looked it up and see nthe 2.5L, 3.0L, 3.7L, and I guess the straight 6 all used the same pump. I see IBOATS also has it for about the same price for a sierra, and ebasicpower has a GLM for $129.95.

[scook]

With people who say a mechanical pump has solid state electronics and, 2-wire connection, I'm not real sure of anything but the Mercruiser part number they start with is the correct one. For a few bucks more, I'll go with a known supplier.

You think I'm on the right track swapping out the fuel pump at this point? Anything I'm missing?

[Cam]

Could possibly be a sometimes clogged pickup in the fuel tank. Try running the boat from a portable tank for a while first, before you plunk down money on a pump. You may even be able to remove the pickup and see if it is screened at the bottom. Easy enough things to do before spending money.

[macojoe]

I removed my ck balls, they were getting stuck all the time!

[spareparts]

have you tried running it with a portable fuel tank?

[scook]

Haven't run on a portable tank or checked the pickup for a dirty screen. Thanks - I'll try those.

[scook]

1) Finally got back to working on the boat. Pulled the sending unit and the tank is "like new" clean on the inside - I can't imagine there's any clog in the pickup tube with it looking that good. Any reason to think I should pull the pickup tube to inspect it? I suppose I could take off the fuel line and blow back through it to be sure???

2) Putting the sending unit back on, what gasket sealer (I'll buy or make a new gasket) should I use? We have some Permatex #2 and some Mil. Spec RTV.

3) Next thing to check. The only thing that changed from before to after the engine running for a while and then quitting is that I installed Pertronix electronic ignition. Talking with my son the mechanic, he said it sounds like a temperature related issue and suggested checking the ignition by firing it up and warming the distributor with a heat gun to see if that will make it quit.

Any more suggestions are appreciated - fishing season is coming up fast and I'm starting to paw the ground.