Engine problem - '85 Mercruiser 170

[scook]

Pertronix electronic ignition last year - starts and runs great (for a while).

Early June ran at approx. 3000 RPM for around 15-20 minutes, ran near idle for a few more minutes before anchoring up to fish - no problems. Maybe a half hour later tried to start up to move a little, idled very rough, wouldn't run up above idle (not in gear - no load). Tried a few times to start again over next hour or two, best it would do is very rough idle, wouldn't run up at all and died.

Yesterday, started with a little gas poured in carb (hadn't been run since Early June), idled and ran great, ran at approx. 3100 RPM for around 20 minutes and noticed RPM's very slowly decreasing, took it down to idle, it got rough and died almost immediately. At idle the oil pressure dropped to near zero - checked oil and it is good. Didn't try to restart - another long trip back on the outboard trolling motor.

Water temp in the river is around 70 degrees if that helps any.

It's got me stumped. Anyone have any ideas?

[smokeonthewater]

Sounds like it may be a fuel problem

[bradford]

Agree with Smoke. Sounds like fuel and possibly water in the fuel.

[spareparts]

does your oil smell like gas? Could be a bad fuel pump leaking gas into the engine, that will make your oil pressure very low and at teh same time cause a fuel delivery issue.

[THEFERMANATOR]

does your oil smell like gas? Could be a bad fuel pump leaking gas into the engine, that will make your oil pressure very low and at teh same time cause a fuel delivery issue.
This is what I was thinking as well. Neighbor went through this on his 4.3L. They didn't put but a small filter after the pump, and it quickly plugged up with rubber from the pump. His carb plugged up, engine would barely idle, and his oil pressure dropped like a rock after a gallon of gas went into the crankcase.

[scook]

I'll do some oil sniffing. Probably should change the fuel water separator filter to be sure it's not water (the tank is full so shouldn't be condensing moisture). I wouldn't think it would start and run great for 20 minutes if the carb was clogged up - this is the second time it's done this. Was leaning toward ignition since it's the only thing that's changed but will work the fuel issues first.

Thanks

[steplift20]

Keeping it simple
A engine needs three things to run
Air
Oil
Gas
I would start there check to make sure all those things are good
Just my 2 cents
I could get lucky sometimes, but definitely check your water separator The gas they sell today is not hood e 10

[scook]

Don't forget spark.

Yeah, I agree - need to check for gas in the oil and address all fuel issues. At the beginning of the season, I emptied the tank thoroughly, drove a few extra miles and filled up with non-ethanol gas and thought this was going to be a trouble free season. 30 year old boat, I guess I've got to expect an occasional problem, but I'd rather it wasn't during fishing season.

[spareparts]

also, if they haven't been replaced recently, replace all your fuel lines, I've been doing that on boats only 5 years old to fix issues. This new fuel whether E or non-E is tough on rubber lines.

[scook]

Hah - Spare, I think you nailed it. I got the boat in '05 because it was doing exactly what it's doing now - ran 20 minutes and died. We changed the fuel line ant it ran OK.

The guy who owned it before me was a complete non-mechanic (knew how to change the oil and that was it). He had lots of money and when he got frustrated with the V-20, he went out and spent $65k on a new 23' Striper WA and told me later that the V was a better boat in the ocean.

They were only going to give him $1700 trade-in for the boat and trailer and he said "no, I love my old boat and I'm not giving it away to a dealer". My daughter did some work for him and got the boat for me for my birthday with the assurance it was going to a good home. I've done a lot of work on it, but I see why he loved his old boat.:clap:

[spareparts]

just replaced fuel lines on a 2008 Intrepid 25 today. It needed it.

[scook]

Do I need to use USCG approved, below deck fuel line, either because it is required or because it is safer than automotive line? I haven't checked automotive pricing but the approved stuff is around $6/ foot at West Marine.

[spareparts]

For inboard in engines use A1 rated fuel line. The automotive line isn't approved and won't hold up as well as the marine hose. Look on line, you should be able to get a better price than that. I think I retail it for $3/ft. West marine has good prices on tackle and electronics, but they raape you on everythign else. Even with my Port Supply(comercial side of West Marine) I can beat their prices on engine stuff most anywhere else. Check with Jamestown Distributors or Ebasicpower.com

[THEFERMANATOR]

Automotive line also isn't meant to be used under vacuum, and will collapse. Learned this one the hard way. I paid $2.69 a foot for 3/8" marine fuel line from my local hose shop.

[scook]

You guys were right about West Marine prices. ebasic power had the hose for about half - next project, I'll plan ahead and buy smarter. I decided I wanted to get it done last weekend, so I went ahead and let WM thank advantage of me. Got my fishing buddy to help me fish in the new line, changed the fuel/water separator filter and plumbed through the transom to the kicker motor line. Got the line installed with no sharp bends anywhere. A little gas down the carb and it fired right up.

Hoping to sneak out early one morning this week to give it a good trial workout.

Funny thing (it's funny now that it's resolved) when I got it running, I looked down and the volt meter was pegged at zero - this is after just putting on an alternator kit recently. I kidded myself that it could just be the gauge but decided to test it. Not running, the battery voltage was good and running, the charging voltage was good, so it was the gauge. I whacked on the gauge for a while and it came up to a correct reading. Another project to do this winter.

[smokeonthewater]

Check the connections on the back of the gauge

[scook]

Will do - Thanks

[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-fuel-pump-mercruiser-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.

[THEFERMANATOR]

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-fuel-pump-mercruiser-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.

[scook]

To recap the thread, this is after new fuel lines, fuel water separator filter, fuel pump and draining the tank and filling with non-ethanol gas. The 15 hp 4-stroke outboard runs off the same tank for long periods with no problem.

[spareparts]

try a remote tank just to eliminate fuel supply as an issue. Take a volt meter with you, when it shuts down, check voltage at the + terminal on teh coil, it should be above 8 volts, if it won't start back up, run a jumper wire from the + terminal on teh coil to the + termoinal on teh bagttery, if it runs then, you're resistor wire(purple/white stripe) is breaking down. Cut the harness back till you can find a purple wire, splice a new purple wire intoit and repalce the purple/white with the new wire to the coil. Also, make sure the wires to the pertronix didn't get chafed when you installed it, make sure the black wires runs to the - terminal on the coil is good and secure. Is that a new coil? Two more things, disconect the tach wire at the coil(grey)and see if it runs better. If that doesn't help, disconect teh shift assist wire at the shift switch(white/green stripe). Becarefull if you disconect the shift switch, it will be difficult to get it to come out of gear. You may have to cut teh switch off to get it to shift. Stay out in open water doing this test(away from docks and other boats)

If that doens't get the job done or if youhave any questions, call me next time your on the boat, I'll walk you thru a few things. David Hall (843) 532-9148

[scook]

Thanks David - I'll try all that stuff before bothering you. I really appreciate your generosity - you saved my sanity a few years ago when I was fixing the water pump and it looks like you may do it again.

Thanks again - Scott

[bradford]

If that doens't get the job done or if youhave any questions, call me next time your on the boat, I'll walk you thru a few things. David Hall (843) 532-9148


That's gold right there.

[THEFERMANATOR]

Doesn't the PERTRONIX need a full 12 volts to work? I thought when you went to a PERTRONIX, it is reccomended to go to a matching coil and do away with the resistor.

[twhrider2]

Ferm is spot on... that's the way mine is set up

[spareparts]

been a while since Ive done one, but they used to require a minimum of 7 volts. I always bypassed the resistor regardless just to eliminate it causing issues. I haven't done one recently, but 12 volts is better than < 12 any day

[scook]

I got their flame thrower coil with it and cut out the resister wire. I've got 12 V plus. I read Spare's suggestion that I should check it right when it pooped out to be sure something wasn't changing as a result of operating the engine - temperature or some other cause. Intuitively, I don't see what would cause the voltage to drop and if it did, would it cause RPMs to decrease as opposed to just dropping off suddenly,to zero. Of course, my intuition hasn't got the problem fixed either.