Mariner 60hp 1988 3cyl randomly dying and not starting back up for some time

[finnishboatguy]

I have a mariner 60hp engine which is dying randomly. It first died when it was WOT and it fully went out. After some time with the cowl off it started back up nicely. After that, it has died multiple times but always started up after about 30 mins of sitting. I decided to let it idle for about 30 mins at the dock until it died, which made me believe it is not a heat caused problem. Every time it dies, it seems to give a good spark on all cylinders but does not even try to fire whilst cranking. I am going to rebuild the fuel pump and replace the fuel lines. But I am still unsure where the problem is coming from and how to fix it. Any help is appreciated.

 

[SteveVT]

Possible sticking carb float/float needle.

 

[emoney]

When it restarts after the 30 min period, do you have to squeeze the bulb again? Have you tried squeezing/checked to make sure it was firm right after it's died?

 

[finnishboatguy]

The fuel pump rebuild kit came in today, I replaced the gaskets etc, and all the fuel lines. It still randomly died with a few coughs after about 10 minutes and didn't start even with squeezing the bulb (it started/exploded a few times for a split second after dying) and the bulb doesn't seem hard like when the engine worked fine. Also, it doesn't need squeezing the bulb after sitting it starts just fine but I do obviously try to squeeze it after it dies but it doesn't help. I was right near the dock when it died so I just paddled back to the dock and left. I'll go tomorrow and see if it starts normally after sitting. I also suspect the needle or float but unfortunately, getting those in Finland might take a few months and by then summer is over.

 

[SteveVT]

It doesn't necessarily need a new needle and float IF the problem is in that area. It could just mean that opening the float bowl, cleaning the float needle orifice and checking float condition and float drop is required. while you're at it, blow out the main jet in the bowl nut.

Check drop after cleaning by alternately inverting and righting the carb out of the motor and listening for float fall.

 

[finnishboatguy]

i'll go and get the boat home tomorrow. Take out the carbs and check and clean them.

 

[SteveVT]

Be careful of the gaskets if you intend to re-use them. I only say that because it takes a long time for you to order new. In fact, you may not want to disassemble the carb further than dropping the float bowl, and removing the float needle and arm. Do quirt carb cleaner into all orifices, and finish with low pressure compressed air.

Of course you can always make the simpler gaskets like the one between the manifold and carb.

Also, if your float is the loose type (without an attached arm) be careful that the float needle doesn't drop onto the floor when you open the bowl up -- unlike attached arm floats, the loose floats don't prevent the needle from falling out.

 

[finnishboatguy]

I cleaned and checked the carbs and I found nothing in them. Both of the carbs were clean but I still cleaned the jets and needle seat. The needles looked fine and clean. But this still didn't fix the problem, it ran just fine at all rpms until it died at WOT. After it died the bulb was completely empty. Like the other times there was nothing we could do to the engine except wait. Even after cranking for multiple minutes, the plugs stayed completely dry. Then after about 30 minutes, it started back up like nothing had happened and ran just fine. I checked the tank pickup hose and it seemed fine.

 

[SteveVT]

This reminds me of a similar problem I had with my old Evinrude, and never fully figured out. There were a few contributing causes, and it did improve somewhat after working on it, but never became fully reliable. So I'm probably not the best person to advise -- I can only give guesses at possibilities. I will be very interested if you do figure it out!

Thoughts:
1.) some kind of vapor or pressure lock forcing the fuel needle closed when the bowl is actually empty of fuel.
2.) some kind of heat related failure of the fuel pump
3.) vacuum/air leak somewhere between engine and fuel pickup in the fuel tank

 

[finnishboatguy]

I guess I’ll have to start trying new things. Also the top bowl had fuel in it but it still didn’t start and the plugs were dry, I’d expect them to be wet if there was no spark. I’ll take some starting fluid next time to see if it starts with that, and a different new tank from my 4hp.