89 5.7 Mercruiser Running Issues.

[Cdaniels5494]

Hello all, new here! Having some frustrating issues with my 89 Wellcraft eclipse. Bought this boat a month ago, guy had just gotten it back from marina, they put new distributor on, changed all fluids and new impeller, hasn’t ran in a couple years.

Upon arrival he was able to start it on the hose in higher idle, ran for a bit and slowly bogged down and shut off. It was leaking through the carb at the accelerator pump shaft.

Brought it home, pumped old fuel out, fillled about 5 gallons and pumped that out as well, then added 60 gallons of fresh fuel with some seafoam, found a buddy with a good carb, got it to start right up at higher idle, ran good, reved up good, idled ok, sometimes would stall but got it to idle in drive for about a half hour while monitoring temp. We took it out to the lake, backed it in the water, fired it up with idle up a bit, came back and it was off, cranked and cranked and couldn’t get go fire, could smell fuel so waited awhile and was able to get it started again but only ran while idling high, died at regular idle. Changed fuel water separator, no change. Noticed this one was leaking too. I took my original in and had it rebuilt.

Put rebuilt one on when i got It back, couldn’t get it to start, it would only try at wide open throttle. While looking into carb could see fuel DUMPING in. Also leaking again through accelerator pump shaft. I then concluded that my mechanical pump was putting out too much fuel. I called all dealers near me, none in stock, and 2 months back ordered!

So i disconnected pump lines and bypassed it, then plumbed in an electric pump with a 5-7 psi output. Was able to get it to fire up, only by pumping throttle, and left it idling up higher, it ran about 15 seconds then cut out instantly almost like you just turned the key off. Tried to start, just cranked. Waited about 5 minutes, tried again and exact same thing, started and got it idled down some, idled 15 seconds or so then just cut out.

I’m pulling my hair out on this one. Fuel line from tank to separator is also new. Spark possibly cutting out? Tomorrow i will install new plugs. Possibly see about if spark is cut when the boat is cutting out. Any ideas would be great, thanks!!

 

[alldodge]

Howdy
First issue was the carb is flooding the motor. Had a carb rebuilt and only by pumping the throttle. Your saying the new fuel pump produces 5-7 psi, if that is correct then the carb needs the float adjusted, because its still flooding

Which pump and part number did you install?

 

[Scott Danforth]

sitting for 5 years, you need to clean your fuel system

the new fuel is just loosening up crud

doubt the mechanical fuel pump was putting out too much fuel, go back to the carb.

 

[Cdaniels5494]

Mechanical fuel pump was definately bad, when motor was cranking it looked like you had the nozzle of a gas can dumping into the carb, when it would fire it was running super rich. All three carbs i had on had the same issue.

Today I replaced distributor, also put new plugs in it. When i got done, tried it out and fired right up, motor sounded awesome and running super smooth, it ran for about 15 minutes, oil pressure good and temp good, idled good, but then while idling just cut out like the key was turned on. It started back up and ran for about 10 seconds and cut out the same way. No spitting or sputtering just cut out instantly.

So, I’m thinking I had two different issues going on, a fuel and a spark, I believe my fuel issue is fixed, now to deal with the spark. Unfortunately it was only me messing with it and couldn’t confirm if there was spark or not. I did Run a jumper wire from battery to + post on coil and still wouldn’t fire. And double checked, carb was getting fuel.

I’m hoping maybe coil is bad and cutting out when it gets warm. I’ll know more tomorrow, going to have my wife roll motor over while i see If i have Spark or not.
Thanks, any other ideas please let me know.

 

[alldodge]

Its not the coil

 

[Cdaniels5494]

I’m at a loss at what it would be then, fuel is still going into the carb when it cuts out.

 

[alldodge]

It might be electrical I'm just saying folks replace good coil by the thousands every year and very rarely is that ever the issue.

The motor had lots of flooding in the beginning, and with it pumping 5-7 psi the fuel pump was good. For it to flood under that pressure just means the float needle seat is the issue or the float needs adjusting

You should have the TB4 ignition, knowing serial number would verify. With it being intermittent it could be the distributor pickup and more so if has the 2 wire and not the 3 wire pickup.

Run though this troubleshooting guide (TB4 and TB5 are the same)

 

[Cdaniels5494]

Today I went out and tried it again, had my wife roll motor over while i held coil wire next to a ground, no spark, went and got a new coil, did same thing and had spark, hooked it up and boat fired right up. Ran for about 15 seconds and shut down again, coil no spark again. Ran a wire from battery to positive side coil, still no spark. What causes coil to get spark?

Just saw your reply, yes it is thunderbolt, I’ll run through what you posted, thanks!

 

[Cdaniels5494]

Started running through that list, i have power from module on the red/white, i do Not have a spark plug gap tester so was not able to figure out the next step yet. Will get one tomorrow, thanks.

 

[alldodge]

Spark gap tester is best, but can take a spark plug and connect to coil wire and ground to block. Your looking for a white spark

 

[Cdaniels5494]

Alrighty I’ll give it a shot and see, heading out of town for the week tomorrow so probably won’t have time to mess with it. I’ll let you know in about a week what I come up with!