Why slowing down

[Ricktravis]

Can someone explain why my Pearson 386 Hull #1 runs at 5.8 knots At 2000 rpm on August 1 when on June 1 at 2000 rpm she ran at 7 knots. The prop is clean bottom has no hard growth, a bit of slime but no hard growth. The motor, a Perkins 4108, is running smooth and maintains the same rpm’s. It’s just that the same rpm’s are resulting in less speed, SOG and speed through the water.

[thinwater]

Originally Posted by Ricktravis

Can someone explain why my Pearson 386 Hull #1 runs at 5.8 knots At 2000 rpm on August 1 when on June 1 at 2000 rpm she ran at 7 knots. The prop is clean bottom has no hard growth, a bit of slime but no hard growth. The motor, a Perkins 4108, is running smooth and maintains the same rpm’s. It’s just that the same rpm’s are resulting in less speed, SOG and speed through the water.

Tide? Or dirty wheel if sensor?

[NYSail]

Obviously I am sure the currents and winds were identical. How is your exhaust elbow? Maybe a lack of flow is causing a bit of back pressure....

Good luck
Greg

[Sailmonkey]

Wind?

Chop?

More “slime” than you realize?

A bag on the rudder?

A smuggling pod on the keel?

[a64pilot]

That slime will slow you down more than you realize.
I had what looked like cat fur on my hull, no hard growth at all. It took two knots off. I didn’t think a little cat fur with no hard growth could do that.
Terrible picture and a close up when it was hauled for a bottom job.

[daletournier]

Originally Posted by a64pilot

That slime will slow you down more than you realize.
I had what looked like cat fur on my hull, no hard growth at all. It took two knots off. I didn’t think a little cat fur with no hard growth could do that.
Terrible picture and a close up when it was hauled for a bottom job.
Attachment 197031

That's my hull now, I really notice the lack if responsivness...3 year old anti foul will do that.

[Reefmagnet]

Comparing to equitable weather, sea and wind conditions and direction, even minor growth on the hull and/or prop will have an effect on speed at rpm. IMO, the prop needs surprisingly little growth on it to significantly affect it's operation. The only other distant second possibilities are weight on the vessel or a slipping transmission clutch.

[JPA Cate]

Rick, in case A64 is right about the slime (and he very well may be: it looks innocuous, but can be quite slowing--and it can grow a lot in a month), clean the bottom and see if that brings back normal cruising speeds. With a clean bottom, it may come back, or you may have had a current with you on the 7 kn. time.

We often sail in a south setting current, and people think it's a "fast boat", but we're up to 3 kn. slower north bound, and also try to stay out of the current.

Ann

[Ricktravis]

Thanks for all your thoughts. I’ll have to get the scuba gear out and do a light
scrubbing.

[Ricktravis]

Thanks for all your thoughts I’ll have to get the scuba beer out and do a light scrubbing

[thomm225]

Either that are just relax and sail and try not to worry about a knot or two unless you are a racer.

I clean/paint the bottom of my boat every 4 years whether it needs it or not

We have guys on CF that do the same thing with tenth's of volts on their solar charging systems worrying over what the exact battery voltage should be

It's a signal that your world is starting to close in on you a little bit and you may need to expand your horizons

[Emmalina]

Originally Posted by Sailmonkey

Wind?

Chop?

More “slime” than you realize?

A bag on the rudder?

A smuggling pod on the keel?

Smuggling pod Ha Ha Ha Love it !