New owner IP-31 hull speed?

Just purchased a 1985 Island Packet IP-31. We are on Anna Maria Island, near Bradenton,FL. We've been out 7 times this month, both on the Intracoastal and in Tampa Bay. "Nomad" sails nicely and is very stable compared to our old Tartan 27'. But, I'm very disappointed with the speed under power. The Yanmar 27HP seems to run fine but peaks out at about 3000 rpm when in Forward. Much soot when above 2800 RPM. Speed is only 4.9 knots, when plowing into 18 knot wind and some chop it drops to less than 2 knots! Some places I have motored on the Intracoastal have almost that much tidal current. I have not checked the prop to see if there are barnacles but before I jump in the 58 degree water, what is "normal" hull speed motoring? I've already seen 6.8 knots sailing and that pleased me. Coming about must take some practice, though. I haven't been successful yet. Mike

Well, gents, I'm a little disappointed that nobody on this forum has responded to my query for over 2 weeks. In the meantime I have talked to a couple of local IP-31 owners whom I've just met and I'm told that I should expect about 6+ knots at best. I have had an experienced Yanmar mechanic check out the engine as well as complete a change of fuel and oil filters, rebuild the raw water pump and replace the anti-siphon loop casting on the exhaust system. It was about 25% blocked with carbon and corrosion and we thought this may be the reason the engine was down on power (unable to really breathe). Turns out after replacement I still have the same problem. I'll now focus on prop condition, barnacles, and possible improper prop size. One good piece of news is that in matching the engine serial number we found that the engine had been replaced in 2002 unbeknownst to me or the previous owner. It probably has only 266 hours on it (and I had assumed the engine hour meter was bad) since the boat is 25 years old.

Couple of things on hull speed of the IP31. If the exhaust is blowing smoke, there is a load on the engine causing more diesel to be dumped into the pistons than can be burned. couple of things can cause that, over proped (too much pitch) or fouled prop. Cutlass bearing or transmission problems could be an issue but not likley and you can check the cutlass by turning the shaft by hand to check for free rotation. My IP31 does about 5.5 knots with a clean bottom, 5 knots is typical. My IP31 prop came over pitched from the factory and the original owner never resolved until I bought the boat and required it fixed before purchase. Of course he did have to have the engine head rebuilt about 20 years into the life of the boat, probaly because of the load on the engine. He never ran it above 2000 RPMs be caue it blew smoke if he did.
I'd put on a wetsuit and go over and check the prop or pay someone $50 to clean the bottom.
hope that helps,
Alan
IP31-17 Dawn Treader, Deltaville, VA

Mike, on comming about, let the wind backfill the jib before releasing to the other side. The 31 is pretty beammy up front and with the full keel needs a little help to comeabout. Of course you do have a very nice v-berth as the trade off.

Thanks so much! Brrrrrr, that's my plan.

Well its got to be warmer there than here in VA....

I have a 1988 IP 31 and I routinely get 5 - 5.5 Kts under power at 2200 RPM. We are in fresh water and the bottom and prop are both clean.

Thanks, I've had the engine checked out so I'm going to go to work on the bottom and the prop. Some have told me that it may have the wrong propeller since it was re-powered in 2002? Thanks for the input. Mike

Gents,
Finally put the boat back in the water with cleaned prop, new bottom paint, replaced the cutlass bearing, too. Today, as others predicted, we motored at 5.0 at 2000 rpm and 6.0 kts at 2500rpm. Thanks for the input. Prop was a mess with barnacles. thanks again to all. Mike

On my fall trip I had 5.5 knots at about 2500 rpm, maxiprop. I will be checking for fouled prop within a few weeks