18hp top speed?

[Chris D]

Hi everyone, long time reader first time poster. First I have to say this is by far the best site on the net for Mac owners. The information and knowledge shared on this site really guided my decision to purchase a Mac. I am looking forward to some great adventures in the years to come.

Quick question, I bought a 2002x in Nov. It has an 18hp nissan 4 stroke on it. I am wondering how fast this motor will push this boat loaded for crusing with 4 to 6 people on board. I bought this with the intention of repowering with a 50hp or higher. However, slip fee's, a new motor, some upgrades and such are driving up my purchase price up another 10K . If this motor will push this boat at 8 to 10kts or so loaded, then I may consider sailing a year with it and repowering next winter when the bank account recovers....

Anyone have any experience with this setup?

Thanks in advance!

Chris

[Don T]

Hello:
There are a couple of owners who sail on lakes with 18~25 hp motors. They can get to hull speed and just above (7~12mph) pretty easily but not neccessarily plane. I don't want to get the "planing" discussion started here boys, OK.

[DLT]

Yeah, I agree with Don. I bet you'll see about hull speed, realizing that this has a non-traditional calculation of hull speed, but not much more. In other words, I'm guessing in the 8-10mph (not knots) range...

Sometimes, when I'm really loaded down, 10 knots is about all I can do. I get the feeling that you could do just about as good with half the HP, which is about what you have... In other words, I think my 20or so more horses is wasted, when I'm heavy, because it sure aint getting me outta the hole...

You really need the horses to get the hull outta the hole, especially when loaded. Once you get out of the hole, that HP can get you some relatively higher speeds...

I don't know the extent of your situation, but I'd probaly run that 18 for a while, recognizing that you ain't gonna pull any water skiers... Get what use out of it you can, and then when it starts to give you trouble, you won't feel bad about replacing it...

Eventually, I want to upgrade to a higher HP, but I'll wait until I have a reason like a broke engine...

[Frank C]

Welcome & congrats on your new boat!
(and with apology to the forum, I'd like to use the word "planing.")

I think you have some good advice above. But since there's some debate about the Mac's "true hull speed," your setup can make a valuable contribution, IMO. I'm guessing that your outboard might get up to 9 or 10 mph, assuming you are alone, without planing. It would be interesting to see if it can accomplish that same speed with 4 persons aboard - but I doubt it. (But - on edit - as Slamjammer says just below, I believe you'll easily be able to empty the ballast tank.)

The "hull speed" of the 26X, according to the traditional formula (dating to 1600s) is about 6 knots, or 7 mph. According to a modern adaptation though, a "modified formula" shows hull speed of the 26X should be 8 knots (about 9 mph). This is for a semi-planing hull, and it's variable depending upon load. Since your 18 hp certainly won't plane the hull, it should just manage to push your Mac to its "true hullspeed." (Simply my observation and guess, I feel the 26X actually begins planing at about 12 mph. But as inferred above, it takes beaucoup horses to increase the hull's speed from 9 mph up to 12 mph.)

But, if your boat can reach 9 mph, by GPS, in flat water, no currents, with only one person aboard, then I believe it will be pretty good evidence that this boat's "non-planing hull speed" exceeds 6 knots. That determination will help to index the theoretical maximum upwind sailing speed of a 26X. (Downwind sailing can more easily exceed hull speed.)

Assuming that you care to do a little testing, I would surely look forward to reading about your results. You have a terrific boat ... Congratulations!

[LOUIS B HOLUB]

CONGRATs. on buying a fine boat...
Emptying your ballast, will be the big difference in speed. But as you know the passengers have to be off the deck in order to keep the boat stable--definately no sailing with an empty ballast.
I betcha you'll be amazed at the boat performance with an 18 HP. My former boat, a Mac 26S, had an 8HP. It did well with an empty ballast, but not sure of speeds since I didnt have instruments. I usually kept the ballast full, however, since we sailed mostly.
Our Mac-X with its 50HP is nice in calm waters...but motoring fast when its rough always begins to get folks in the cockpit wet. The factory videos of the Mac X with the 50 HP are fairly accurate in my opinion.
Happy & Safe Sailing to you and yours...
, The Holub Boat

[ronacarme]

My 2001 X with Evinrude 9.9 4 str and 7 pitch prop did about 7.5 mph at WOT with ballast pre bottom paint and now more like 7.2 (all gps and loaded to cruise), all as intended.
Ballast dumping? Only as we pull up the ramp on the trailer. We keep ballast tank full at all times with boat in the water. Could perhaps blow out ballast with a 3psi 12 v air pump but have no need to try.
Unlike most, we bot the X only for its roomy, partly standup, well laid out, live aboard for a couple of weeks, interior. The unexpected bonus was that it self steers (except downwind). Otherwise we would still be on our '88 D....sailed faster but not the easy living of the X.
18 Hp2 str? On my X maybe 10 mph WOT and half the range, tho likely longer term reliability than my motor (carb stopped the motor twice since 2001 which is twice as often as any small 2 str
I have had in the last several decades).
Good sailing to you.
Ron

[Mark Prouty]

I bought this with the intention of repowering with a 50hp or higher. However, slip fee's, a new motor, some upgrades and such are driving up my purchase price up another 10K . If this motor will push this boat at 8 to 10kts or so loaded, then I may consider sailing a year with it and repowering next winter when the bank account recovers....

Anyone have any experience with this setup?

Thanks in advance!

Chris

Live with it till you can afford to repower. I haven't had experience with your setup; however, I've had experience traveling with sailboats without planing hulls and Mac sized motors. There are often times when you have to head into the wind and buck the waves. I have been able to proceed in these conditions (yee ha). Under these same conditions, other sailboats could not make headway and had to stay behind. They actually had negative forward speed.

In addition, a Mac sized motor is nice when a destination is right there but wind conditions aren't right - you can see it on the horizon but with a conventional sailboat it is out of reach because 6mph is just too slow.

From my experience, some the Mac's sailing abilities are compromised - pointing ability in paticular. In my humble opinion, the ability to motor at increased speed more than compensates this.

With 20 boats and a close reach, I found I could sail as fast or faster than the best of them. When on a course requiring good pointing ability, I'd have to tack more than most others. Instead of tacking, I'd compensate by lowering my motor and powersailing. The four stroke was so quiet, nobody noticed.

Danger, Danger. Carefull with bigger motor.

Danger Chris D! Danger!!

[Chris D]

Hi guys, thanks for all of your input. I think for this season I will take your collective advice and try the 18hp out. I guess I can always upgrade mid season if I find it is not doing for me. Good to know that I may get 6-10 MPH out the motor, that would be fine for me. I have a 12 foot zodiac tender. With my 15hp 2stk it does 25Mph with just me in it. I guess I can drag it behind and zip around in that when I feel the urge to go faster..

Thanks again!

Chris

[Zoran]

Looks like I have the closest setup to yours with 30 HP 2 stroke Nissan on my X. At the beginning I was achieving 11 kt WOT every time, no ballast. But than I added 25 gal fresh water tank and 2 deep cycle batteries at the front, floor, galley drawers, shelves, back deck etc and now I can get it to 10 kt only in ideal condition (read almost never). When I am emptying ballast on the water I noticed that I have quite a bit of water left at the ramp.
On the other hand i got that engine with the boat and i am still thinking it is not worth replacing it as long as it works.

Zoran