Making very little power

[chrick]

Hi Afourians,

I'm new to these forums, as I am new to Atomic 4 maintenance - how great that this resource exists! My girlfriend has a Pearson 30 with the venerable A4 in the bilge, and it is not making enough power, and has me stumped. I have reviewed the other threads, and feel like I have tried pretty much everything, although given the motor still isn't making it's power, I clearly have not found the problem yet. Here's some information that seems relevant:

• New carburettor installed - motor now starts and runs reliably, just with very little power.
• Prop cleaned, shaft checked for anything which might bind - turns freely, and there is no further sign of fouling (it was covered in barnacles previously).
• Ignition is the electronic variety, plugs are new, plug wires are new, cap and rotor look new, although I don't know their age.
• Cylinder 1 plug is sooting up quite a lot, cylinders 2 and 4 look lovely, and cylinder 3 looks mildly fouled when I pull them to check.
• All plugs making good, clean spark.
• Compression checks out around 80-90 on all cylinders.
• Electric fuel pump and inline filter are new - and bypassing all but the fuel pump and drawing fuel from a jerry can does not change anything.
• Cracking open the flame arrestor to make sure air supply is adequate doesn't change anything.

The motor starts just fine, and does the usual running poorly in forward and better in reverse, revs fine in neutral, etc. It's just not making power - and I don't think it's rev-range related, as even in reverse, when it revs higher due to the transmission gearing, it still isn't making much power - i.e. it won't rev right up, just goes a little higher.

The motor seems to be happy to run at low power for extended periods, we have actually been out sailing with it a few times and have managed to get out and back, just very slowly. Certainly if we have to fight a headwind or get unstuck after running aground in the mud of the channel we will have a hard time.

Any thoughts or things that I should check? I would really like to just have this engine work - it's making boating stressful instead of stress-reducing!

Thanks,

Chris

[Peter]

Hi Chris,

You have come to the right place - these folks are awesome and have an enormous wealth of knowledge and experience.

Have you checked your exhaust system for blockages? Beyond fuel and spark, which you seem to have, good exhaust flow is also important.

You have a lot of new stuff on the motor, and as our administrator occasionally reminds us, we sometimes think "It couldn't be X because it is new", and then it turns out to be exactly X.

I.e. - assuming because it is new it must be ok can be a pitfall.

A fuel pressure gauge - very cheap and easy to install - might be a useful diagnostic to ensure fuel flow is adequate.

Have you tried choking the engine up to see if it improves power?

And have you checked to ensure that the throttle linkage is indeed opening the throttle all the way?

One more thought - plug wires were changed. Firing order is 1-2-4-3, where 1 is the cylinder closest to the flywheel. If 1 and 3 are interchanged, that might be the issue.

Best,

Peter

[Dave Neptune]

Chris, as per Peter try engaging the choke to see if the power increases a bit. This will tell you if the carb is to lean.

Second check bring the engine up to a bit of a load in forward against the dock lines if you can. Once the engine is working against the lines pull one spark plug wire. If the RPM drops all is well if it increases slightly you have an exhaust blockage.

How long since the exhaust has been replaced?

A blocked exhaust can also darken the plugs color too.

Dave Neptune

[JOHN COOKSON]

Maybe you are over propped. What boat and what size prop on it?
For the next event give your girlfriend copy of the Moyer manual.

TRUE GRIT

Edit: Noticed the boat is a Pearson 30