48 SPL only revs sometimes...need help!

[ledzep244]

I recently bought a boat with a 95 Evinrude 48 SPL. The problem I'm having is that the engine idles great, but doesn't like to rev above about 2k rpms most of the time. It just bogs and smokes a lot.

I have changed the plugs, changed the fuel, changed the tank and primer bulb and quick fitting, cleaned the carbs, checked the throttle position, and run seafoam through it. I even disconnected the tan wire that runs to the temp sensor.

Nothing has helped. It doesnt matter if its in gear, in the water, or just in neutral in the driveway. Butterflys open in sync. A little bit ago it started revving great, 5500 rpms, but after about 5 minutes it started bogging again.

If I manually choke it with my hand it just dies. It seems to be running too rich or not burning all the fuel, plugs are wet.

Anyone know what I should try? I have the boat outside and have today to work on it. Ive read every related post on the internet I swear.

Please help!

Thanks

Daniel

 

[Daviet]

Re: 48 SPL only revs sometimes...need help!

Start with some basic checks, compression and spark. If they are ok you need to move on to the fuel delivery system. Try squirting fuel into each carb and see if it picks up and runs.

 

[ledzep244]

Re: 48 SPL only revs sometimes...need help!

Compression and spark are good...if i squirt fuel in carbs it kills motor. Running rich.

 

[Daviet]

Re: 48 SPL only revs sometimes...need help!

Are the plugs in good shape, fouled, gapped properly?

 

[ledzep244]

Re: 48 SPL only revs sometimes...need help!

Yes, I have tried 3 sets of plugs, all gapped properly. When it decides it wants to rev it revs great. Its an intermittent problem. Its getting gas for sure. Im starting to wonder if it could be electrical.

 

[Daviet]

Re: 48 SPL only revs sometimes...need help!

You can use a timing light to check spark on each cylinder when it is acting up, maybe you have a power pack malfunctioning at times.

 

[ledzep244]

Re: 48 SPL only revs sometimes...need help!

You can use a timing light to check spark on each cylinder when it is acting up, maybe you have a power pack malfunctioning at times.

Will powerpacks intermittently fluxuate the amount of voltage they send out?

 

[Daviet]

Re: 48 SPL only revs sometimes...need help!

A power pack can intermittently misfire a plug.

 

[ledzep244]

Re: 48 SPL only revs sometimes...need help!

Is there a way to test it?

 

[ledzep244]

Re: 48 SPL only revs sometimes...need help!

*UPDATE*

I bought a spark gap tester and set it to 7/16"...it sparks great on idle, but when I rev it and it starts cutting out/bogging the spark becomes less consistent, and dissapears for moments. It does this on both cylinders.

Now that I know it is not sparking properly while revving...does anyone know what electrical component could be causing this? It really seems like it is being electrically rev limited, but I disconnected the temp sensor. I am thinking powerpack or stator...anyone??

 

[ledzep244]

Re: 48 SPL only revs sometimes...need help!

anyone? I don't want to start replacing electrical components if I can isolate the problem...

thanks..

 

[boobie]

Re: 48 SPL only revs sometimes...need help!

Without an OEM factory service manual and some test equipment all you can do is throw parts at it.

 

[ledzep244]

Re: 48 SPL only revs sometimes...need help!

*UPDATE*

For those of you who read this post in the future trying to fix your own motor, I found the problem. After pulling the plate that holds all the wiring off so I could check all the wires, I found that the red wire with the purple stripe had been shorting out to the block. It was almost completely worn through. Repaired the wire, revs perfect.

 

[Crashsector]

Re: 48 SPL only revs sometimes...need help!

Can you elaborate on where this block is? We are having exactly the same problem as you described. Are you talking about the grounding block on the starboard side of the engine?

My thread, for reference:

http://forums.iboats.com/showthread.php?t=500826

--Andy