1997 75 hp idle and starting problems

[dickjustice]

At the end of last year the engine would not run at wide open throttle so a couple of weeks ago i rebuilt the carb and fuel pump, replaced all the fuel lines and replaced the spark plugs. It ran better than it has in a long time and would even idle for long periods. Yesterday afternoon, after running fine that morning, it began to not want to idle and this morning when i went to crank it would not idle at all. The only way to get it to crank was to open the throttle up but when i pulled it back into neutral it would go dead. I finally got it to go into gear without dieing and it would run at 2500-5000 rpms plus all day long but as soon as got anywhere near neutral it would go dead. The only thing else ive done is add a can of seafoam to the tank but it has run fine since then. Any ideas what could cause this? Also, if i get this problem fixed, how do i increase the idle rpms, before my latest problem it was idling in neutral in the water at 800-900 rpms.

 

[bentle]

Re: 1997 75 hp idle and starting problems

I would do the link and sink found at the start of the forum page sticky.
Does the primmer bulb feel soft and kinda flat when it dies? If so then something is restricting fuel flow.
This could be bad primmer bulb.
Fuel line may be collapsing do to age, or pinched off.
Fuel vent plugged not allowing tank to breath.
Fuel pickup tube in the tank may be plugged not allowing enough fuel through.
May not hurt to do a compression and spark test as well. Post what your results are.

 

[pnwboat]

Re: 1997 75 hp idle and starting problems

bentle has some good things to check.

I had a similar experience as you did after replacing the metal fuel line fittings on the carburetors. After I got everything back together, the motor ran fine but after a short while, it wouldn't idle. Motor just died if I brought the throttle back to the idle position. Ran fine at WOT. I took the cover off of the motor and squeezed the primer bulb 3 or 4 times. Gas squirted out of the vent holes on the lower carb. Obviously the needle valve was stuck open. Took it home and discovered that when I screwed the new brass fitting into the carburetor, it shaved some metal filings of off the threads inside of the inlet. The metal filing were sitting in the inlet passage and got caught between the needle valve and seat. Blew them out and it's been fine ever since.

Do you have an in line fuel filter between your fuel pump and carburetors? If not, maybe after you rebuilt the fuel pump, you inadvertently dislodged a small piece of debris or hose and it got stuck between the needle valve and seat?

To adjust the idle, turn the idle adjustment screw located on the tower shaft. It has a lock nut to keep it from working loose. See the red arrow below.

 

[dickjustice]

Re: 1997 75 hp idle and starting problems

All the fuel lines including the bulb are new and I also replaced the fuel filter. Since the boat is at my cabin an hour away I went ahead and pulled the carb and brought it home with me. When I pulled the carb I squeezed the bulb and a good stream of fuel came out the fuel line going to the carb. So I dont think its a fuel supply problem to the carb. Tonight I will take the carb apart and hopefully something simple is clogging it up. I might be wrong but I was thinking maybe the seafoam broke something loose and its clogging up the carb. Not sure about spark and compression but I pulled the plugs also and nothing looked out of the ordinary with them. Whats the best way to perform a spark test?

 

[pnwboat]

Re: 1997 75 hp idle and starting problems

I would look for any signs of crud that may have broken loose. Take the fuel bowl off over a clean piece of paper of something so that you can see if anything comes out, and check inside the bowl. Do the same when you remove the needle valve to see if anything is stuck on or around the needle valve itself. Sometimes when you're repeatedly removing and installing the rubber fuel lines on the barb fittings at the carbs, the inside of the hose gets a little torn up and the pieces can get caught in the carburetor.

Best way to check for spark is to with an inline spark checker.

http://www.amazon.com/dp/B0002STSC6/ref=asc_df_B0002STSC62023932?smid=ATVPDKIKX0DER&tag=hyprod-20&linkCode=asn&creative=395093&creativeASIN=B0002STSC6&hvpos=1o5&hvexid=&hvnetw=g&hvrand=20087363011633571707&hvpone=&hvptwo=&hvqmt=

 

[dickjustice]

Re: 1997 75 hp idle and starting problems

Put the carb back on it today and still the same thing so after getting it running at a higher rpm for a minute i pulled the plugs to check them. The top two plugs had a little black on them like normal but the bottom plug looked brand new like its not firing. Also noticed that two yellow wires coming from the top of the engine were very hot and where there is a connection is black like its about to melt the rubber. I will try to post a picture when i figure out how to.

 

[dickjustice]

Re: 1997 75 hp idle and starting problems

 

[pnwboat]

Re: 1997 75 hp idle and starting problems

If you're certain that the carburetor is clean and working correctly, I would begin to suspect the fuel enrichment solenoid is stuck open dumping too much gas into the intake. Just pinch off or disconnect and plug the small line that goes from the bottom of the carburetor bowl to the fuel enrichment valve.

Had the exact same problem with the yellow wires from the stator to my voltage regulator on my motor. If you look closely at the picture I posted on reply number 3, you'll see I've outlined a terminal block with a yellow square. I replaced the bullet connectors with a terminal strip. Cut the bullet connectors off, soldered some eyelets on the wires and secured them with screws. I have not had that problem any more.

 

[dickjustice]

Re: 1997 75 hp idle and starting problems

I will check that tomorrow, but right now the only way to get it to crank is to run up the throttle and push in on the key.

 

[pnwboat]

Re: 1997 75 hp idle and starting problems

Usually the only way you can get a flooded motor started is to open up the throttle like in neutral fast idle. If the problem is the enrichment valve stuck open, once you get it going and warmed up it should idle normally with the fuel supply to the valve cut off.

If you determine it is the valve, you might be able to get it unstuck by squirting some carburetor cleaner into the fuel inlet/outlet and pushing in on the ignition key, or tapping on it. You should hear or feel the valve "click" when you push in on the ignition key. Repeat several times.

 

[dickjustice]

Re: 1997 75 hp idle and starting problems

So flooding would cause that bottom plug to stay clean and appear not to be firing? Sorry for all the questions, Im just trying to learn all i can. I did notice that when it was going dead it was like it was coughing fuel back out the front of the carb. not much though. It also would sounded almost like it was backfiring through the carb sometimes when trying to crank it.

 

[pnwboat]

Re: 1997 75 hp idle and starting problems

It's hard to say what the plugs should look like right now because you really don't know exactly what's going on. The fact that it runs fine from 2000 to 5000 RPM's would indicate that all cylinders are firing, you have good spark and the motor is more or less working the way it should. Something is happening at low RPMs. Just a process of elimination, starting with the simple things first. There is a possibility that a reed petal may be broken or cracked but that's a little more involved and the motor doesn't typically run well at any RPM when this happens.....but you just never know. Once you get to the bottom of it, the pieces of the puzzle will fall into place.

 

[dickjustice]

Re: 1997 75 hp idle and starting problems

About to head up to check on it, one last question, if it is the enrichment valve, and i cant get it unstuck, is there anyway to bypass it or cut it off to be able to use the boat until I can get a new one? And dont know if I have said it yet but thanks for the help.

 

[pnwboat]

Re: 1997 75 hp idle and starting problems

Yes, just disconnect the fuel supply line that goes from the carburetor bowl right where it connects to the valve and stick a small bolt in the end of the line to temporarily plug it up.

 

[dickjustice]

Re: 1997 75 hp idle and starting problems

Enrichment valve working, good spark to the bottom plug but after I get it running the bottom plug is clean unlike the top two, couldn't tell for sure that it was milky but it appears that way. And after it I shut it down it Looks as though steam is coming out of the carb. Blown head gasket maybe? If so how hard is it to replace?

 

[pnwboat]

Re: 1997 75 hp idle and starting problems

Head gasket is very easy to replace. Water in the cylinder is usually head gasket or Exhaust cover gasket and once in a while the stainless steel baffle under the exhaust cover cracked.

 

[dickjustice]

Re: 1997 75 hp idle and starting problems

Pulled the head and replaced the replaced the head gasket, old gasket appeared to be fine, cranked it up and still doing the same thing, bottom cylinder still getting water in it. How hard is it to replace the exhaust cover gasket? Good thing is the there did not seam to be any damage to the pistons and cylinders.

 

[pnwboat]

Re: 1997 75 hp idle and starting problems

Exhaust cover gasket is a little harder because it's harder to get to the bolts towards the bottom. Also be careful when removing the bolts. Sometimes they're corroded and if you aren't careful, it's easy to snap one off. While you've got the cover off, it's good to inspect the small water passages inside the cover and remove any small pebbles and grit if you find any. Inspect the stainless steel baffle very carefully for any cracks too. The baffle itself will probably be pretty warped too but as long as you don't see any cracks, it'll probably be OK.