Minimum HP needed to power a CD25 on East coast near Boston

[Adrift54]

I am interested in what the minimum HP is for a CD25....I am replacing my 2000 Tohatsu and am considering a Lehr 5 HP, but am unsure if it will provide sufficient power...just need to motor to and from my mooring at times. I need to keep the HP low because I need a lightweight motor so I can lift it out after sailing. The barnacles are too much where I am moored, so I want to pull the motor after each sail. Appreciate opinions based on minimums used. Boat located near Boston, so there are 1 to 2 currents to deal with.

[tartansailor]

Hello Adrift, and welcome to the forum.
You are sailing one of the finest boats that this Country has ever produced.
Congratulations.
Some folks here get away with a 4hp.
I have an 8 hp, and hoist it out of it's well with my halyard and a snatch
block attached to the back-stay.
Some have thought of rigging up some sort of under water container
that could either be pumped out or to add bleach to keep the critters at bay.
Hope this helps.
Dick

[pete faga]

Dick. How do you attach the snatch block to the stay? Any pictures handy?
Thanks Pete
Adrift.My 6 hp weighs about 65 lbs/20 inch shaft which is not too difficult two or three x a year to take out and clean.Since you are on a mooring you probably have or access to a tender.Take a stiff long handled brush to the shaft every couple of weeks.You can also clean from above from the lazarette.If you are dealing with 2 currents like the Hull gut you might have to time your transits if you opt for less HP.I tried Sea Hawk paint 50 dollars a PINT worked just ok last year but it did limit build up.If you are close to Scituate you are welcome to try it.I pint goes a long way there is not mech area on a shaft
Pete

[Steve Laume]

Here goes the current argument for more power again. This always bugs me.

The power of the motor drives the hull through the water at a certain speed. The maximum speed would be the hull speed of your boat. In flat water with no current and no wind, lets say hull speed is 5 knots. Your speed through the water would be 5 knots as well as your speed over the ground. If you introduce a 2 knot current and head directly into it your speed though the water would remain at 5 knots but your speed over the ground would drop to 3 knots. No amount of additional power is going to drive your boat past it's hull speed through the water. If you turn around and run with the current you could do 7 knots over the ground but your speed through the water has not changed.

The only valid argument for more power would be to punch through waves or drive the boat into a head wind. Even in this instance a different prop might make more difference than a bigger engine.

With a gas engine that doesn't care if it is not running well up into it's power band, I suppose it wouldn't hurt the engine to run it at lower speeds most of the time. If your primary concern is sailing then it could do more harm. The bigger engine will be heavier and that is not only inconvenient when handling the engine but adds weight to the stern. If your boat is bow heavy it couldn't hurt to hang a few more pounds on the stern but that is usually not the case with our boats.

I bought a Typhoon one time that had a 6HP engine on the back. To counter this weight the PO added a great deal of lead to the forward area of the boat. While this balanced the little TY it he also had to raise the water line.

If you were planing to do a bunch of long distance cruising where you were going to be motoring for extended periods a slightly larger motor might be prudent. For the conditions you are describing I would feel perfectly comfortable with a 4 HP motor. If you only wanted to get back and forth to the mooring 2HP would do the job.

You could definitely pull a 2HP motor and leave it down below when not in use. The 4HP is probably a good compromise.

I'm sorry if my rant offends anyone, Steve.

[Neil Gordon]

>>Here goes the current argument for more power again. This always bugs me. <<

Me, too. The only truth in it lies, I suppose, in the apparent wind, which is a real force to overcome. So if the current is 2, wind is 15 and boat speed is 5...

Going downwind and with the current, speed over ground would be 7 and the apparent wind would be 8.

Upwind and against the current, speed over ground would be 3 knots and the wind would be 18 knots. That's roughly 4x the wind force... and you might not get hull speed against it. Even where you have sufficient HP to push the boat, there's lots of effort used to keep the bow pointing the right way, with all that extra rudder action causing more drag. If you don't need more HP, it surely feels like you'd go faster if you had it.

[tartansailor]

Dick. How do you attach the snatch block to the stay? Any pictures handy?
Thanks Pete

Sorry Pete, no pics. The boat is buttoned up.
The snatch block is on the back stay and it's snap shackle goes to
the halyard shackle which lifts the engine harness.
Hope this helps.
Dick

.

[riveredge]

I have a Honda 5 hp and it works fine. I think its noisy and someday I'm planning to upgrade to a Tohatsu 6 hp that will also charge my battery.

[riveredge]

To elaborate I think the 5 hp is adequate for the CD25 but slightly underpowered. A four-stroke 6 hp engine is perfect for the boat in my opinion.

[Adrift54]

Thank you all for your responses. I feel I am in great shape to make a decision. Very much appreciated.

[CaptDavey]

I just noticed that this thread discussed having to lift the engine out of the well to keep the barnacles at bay. I have an 86 lb. Johnson 9.9hp on my TyS, so I cannot easily lift it.

I solved the problem with an outboard motor flushing bag. After I tie up, I push the bag down into the well so it's below the prop and lift it so that it covers the motor. I then put a fresh water hose into the bag and run it to displace the salt water with fresh water. (I plug the drain hole, but I could just attach the hose to the hole.) Then I start the engine, while still running the hose to let it flush with fresh water. Finally, I leave the engine in the bag, full of fresh water. When I next use the boat, I just untie the bag and push it down and retrieve it -- leave it on a piling upside down to dry until I need it.

Obviously this won't work for a moored boat, but mine is in a slip. In case anyone is interested in this solution, I bought the bag at http://www.burgees.com/FlushingBag/Model_SB2.htm

I suppose you could do this on a moored boat by putting the bag in place, then pumping out the sea water, and pouring in fresh water from a 5 gal jerry can. The other advantage to using the bag is that it cleans the sea gunk from the engine and probably extends the life of the water pump.

[Maine_Buzzard]

Very interested to hear how the Lehr outboard works out for you. I love the idea of a propane outboard and had once toyed with the concept of a propane fired Atomic Four, thinking it would be easier and cleaner to run the engine and stove on the same 20# bottles. I would have needed room for four - five propane bottles...

[Markst95]

I was looking at the Lehr too but wonder about build quality, saw some problem posts from people who had one for less than a year.