Drastic affects of a fouled prop - Perkins 4-108

[MikeNZ]

I thought you might be interested to know just how bad a fouled prop can affect motoring performance.

We have a 46 foot Farr centre-cockpit yacht. For the last 12 months we have kept her in the Bay of Islands (1,000kn from our usual home marina) and didn't get the chance to do our normal anti-fouling. We came up for the Xmas holidays and first day out we couldn't get more than 2,000 revs. At anything more than 1,700 revs she (yes, our old Perkins 4-108 is a 'she') would black smoke. Max speed was 5.5 knots. Temprature was 90 degrees C (normally 80 degrees).

So....back to the marina and got my boys to get out the scuba gear and dive down and clean things up. Prop was covered in small barnacles and some larger muscles on the shaft (how embarrasing!). They scraped it all off and did the rudder pretty thoroughly and a small amount of the hull (although rudder and hull were pretty clean with just slime).

Next day, after rewarding the lads with plenty of beer and food, the difference was amazing. She revs to 3,000 rpm, temperature is back to normal, 6.0 knots at 1,900 rpm, no black smoke. All is fine!