3.0 Liter, alpha one - runs rough when hot

[Zeekdb]

I have a 89 mercruiser that has been running great up until yesterday, after pulling the kids in the tube for a couple of hours, it started bogging down on throttle up, missing a little and stalling out on idle. I replaced the plugs and took her out for a test drive today, she ran great for about an hour, then suddenly, it started missing and bogging down. I had trouble powering it onto the trailer, a couple of back fires and pops, it stalled out. After cooling down, I ran it at home with the muffs and it ran great again. It seems that under load and hot is when this motor is acting up on me.

Any Ideas?

Thanks

 

[Haut Medoc]

Re: 3.0 Liter, alpha one - runs rough when hot

Welcome to iboats.......
Water in your gas......
Change the water separating fuel filter for starters, & see if that fixes the symptom......​

 

[Zeekdb]

Re: 3.0 Liter, alpha one - runs rough when hot

Thanks Haut - I don't think I have a water seperator on this model, after hours of going through manuals and stopping at marinas, someone told me that this was an optional item. I will test tomorrow after, changing the fuel filter in the carb and letting it idle for a couple of hours trying to burn out the water.

 

[Zeekdb]

Re: 3.0 Liter, alpha one - runs rough when hot

I took off my fuel pump and took the bowl apart to find a fuel filter that was not much but mush, I don't think it has ever been changed! I took it out and will run it tomorrow without the filter as I ordered one. Does anyone know if this is a bad idea? Thanks

 

[Bondo]

Re: 3.0 Liter, alpha one - runs rough when hot

Does anyone know if this is a bad idea?

Ayuh,........ That's a Bad Idea..........
Unless you Really want to Rebuild the Carb when All that Crap goes There instead........

The Water/ Fuel seperators are pretty common,+ Cheap,......
Buy 1,+ install it Ahead of your fuelpump..............

 

[Dakota47]

Re: 3.0 Liter, alpha one - runs rough when hot

Change the fuel filter before running that motor..(i would not run it without)

 

[Zeekdb]

Re: 3.0 Liter, alpha one - runs rough when hot

There is another filter in the tube that goes into the carb, a secondary filter from the prefilter in the bowl....Still a bad idea?

 

[WAVENBYE2]

Re: 3.0 Liter, alpha one - runs rough when hot

When you say HOT, How hot ?? Is you cooling system working OK??

 

[Zeekdb]

Re: 3.0 Liter, alpha one - runs rough when hot

When I say hot, It is normal operating temperature, it runs perfect when I first start it up, it acts up after running it for about 30 minutes or so, under load.

 

[Bondo]

Re: 3.0 Liter, alpha one - runs rough when hot

Ayuh,.........

You've Got to Clean up your Fuel System,........ Not make it Worse.........

That little "Filter" in the Carb's Inlet won't do Squat.............

 

[Zeekdb]

Re: 3.0 Liter, alpha one - runs rough when hot

Makes sense, I will put a new filter in before running this thing. Thanks for all your input and possibly saving me more headaches in this wonderful world of boating.

 

[Zeekdb]

Re: 3.0 Liter, alpha one - runs rough when hot

The fuel filter did not do the job, I started it up, ran it for about an hour, ran like a top. At this point, I was thinking I am all set, then, Pop, boom, Pop...another misfire, I was very discouraged at this point, having to idle it to the boat ramp.

 

[tic]

Re: 3.0 Liter, alpha one - runs rough when hot

No expert here, but if it is indeed water in the fuel, a can of dry gas (isopropyl alcohol) works wonders.. We see this condition all the time when snowmobiling a bottle of fuel system drier always seems to do the trick.

 

[searay_89]

Re: 3.0 Liter, alpha one - runs rough when hot

i have the same motor, same year.
i hope you have more success than I have.
i have been chasing this problem for 4 years! ran perfect for 14 years before that!
in addition to your problem, now mine will not restart after i turn it off. has to cool all the way down.

i have replaced everything, fuel, filters, ignition, carb etc.

my next step is to run it long enough to get it to the middle of the lake, pull the plug, and swim away.

good luck

 

[Zeekdb]

Re: 3.0 Liter, alpha one - runs rough when hot

Here is the rest of the story, I finally stopped by a mercury dealer and asked the mechanic what I should do next. He told me to change the condenser, when it gets hot, it starts to break down, I did, and , finally, after a week of troubleshooting, I am feeling great! My boat is finally trustworthy! This is a great forum and I have learned a lot about my motor. Thanks Ya'll