Sudden loss of power in gear

[ereuter]

I was cruising along today at around 6-7 knots in my '78 Pearson 30, and the motor suddenly lowered its RPM significantly. I tried throttling up, and the RPM dipped a little and then just stayed steady at the new lower RPM. I could throttle down to idle and back up, but not as high as usual.

I put it in nuetral, and could rev the engine up no problem. So, something is suddenly limiting it's RPM, but only under load.

I parked on the mooring, and found a ton of seaweed on the prop and shaft. I cast off and buzzed around a little, but it still doesn't seem to be going as fast as usual. The boat is very new to me, so it's hard to guage.

I'll take the GPS out next time and see if I'm getting up to hull speed or not.

Any thoughts on this?

Some additional info:

1. I fouled the prop with the dinghy rode last week. Everything seemed fine afterwards. Motored an hour or two since then. Prop looks fine, shaft isn't wobbling, etc.

2. I changed the cap and rotor a couple days ago when I couldn't get it started. Turned out to be a crap battery.

Thanks!

Eric

[ereuter]

Never mind. One of the plug wires had come loose from the cap. All is well...

[tenders]

I think you need to apply Occam's Razor and shave the stuff off around your prop.

That means, rule out the most likely cause before assuming anything more complicated. The simplest cause is a prop fouled by seaweed, which fits every symptom and which you actually observed.

The second simplest cause here is something misaligned between the rotor, cap, and ignition wires. You could be missing on one or more cylinders.

The dinghy rode incident doesn't sound like the problem.

[ereuter]

Thanks, tenders. It was both. Everything is fine now...

I just get nervous because I am moored in a VERY strong river (Piscataqua), and loss of the engine between the mooring and the ocean would almost certainly be catastophic.

Eric