MacGregorSailors.com

..

Benefits of twin engines

1- you never have to cancel a day trip because your engine quits.
2- Smaller engines = the ability to usually unbolt it and take it in a taxi to the nearest service guy.
3-two engines seldom quit for the same reason (unless you run them out of gas), so you almost always have enough spares to keep one running.
4- Motorsailing on one engine (the leeward one) keeps the prop in the water most of the time, even during heavy weather.
5-On a multi-day upwind moter trip you only have to run each one 1/2 the time.

Disadvantage = more cost per hp.

MM= big advocate of twin engines (FYI my 6hp are out 18 hp's are now in).

MM= big advocate of twin engines (FYI my 6hp are out 18 hp's are now in)

MM, why is the 18hp "in"?

Now if I could unload my Evinrude 50hp and get to 18s even Steven....I would really consider that. The benefits of two smaller engine are obvious...flexability, safety. Of course, if you're someplace with no taxis you can carry the thing somewhere for repair.

I wonder what kind of hardware would be needed to connect them to the helm??? Would this config. make more room on the transom for easier water entry?????

How about one big rudder right in the middle??? Oh, boy...

Gerald Gordon wrote: ... close to completing my centerboard mod. It will no longer tilt down but rather work like dagger board on the M. I really hope the X-dagger mod will prove worth the trouble. I should be able to create 740 sq inches of wet area. I hope I won't have to steer so much. I should also be able to hold a course better when turning on the awesome power of my Evinrude 50hp.

Sorry, not trying to be critical ...
I have no idea what objective is intended with the mod,
but I suspect it must accomplish less than intended.

I cannot imagine sailing with such an implementation, so am looking forward to empirical feedback.

Gerald,

The twin 18 hp. Nissan (Tohatsu) engines are 'in' in my book because:

(1) Best price per hp. + long shafts available.
(2) Best hp. per weight for twins
(3) Easy to repair
(4) Available/repairs most places (world wide).
(5) You can get them delivered free (like from Cabalas, etc)
(6) Have both electric and pull starts on engine + alternators.
(7) Low footprint, fit easy on boat
(8) If needed, Cabalas and a couple of other places will allow you to put them on a credit card and pay off over 6 months.
(9) Extremely reliable & parts are not outrageous.

Also, 36 hp. is plenty for the MAC if you spend most of your time sailing or long distance motorsailing.

MM

MM,
I did see the Tohatsu engine. Do you think that two 18's will produce 36hp? Or is there a gain, or loss, maybe. What do you think would be the top speed for the X @36hp?

I read in one of your posts that your CB modification yielded some good results. I'm now able to deploy my CB like a daggerboard. It can go vertical 10-12 inches and retracts completely into the trunk. I'll be trying it out this weekend.

Frank C wrote:

I have no idea what objective is intended with the mod,
but I suspect it must accomplish less than intended.

Hello Frank C,

I'm trying to create more resistance below the waterline by having a six foot long keel x 10" deep. I imagine that the hull and the keel will provide more resistance and the boat will not blow sideways as much because water can't get over and around the hull/CB as easily.

The stock X setup is a swing keel (CB) or some such name. It does not take advantage of the hull bottom to stop the water like V hulls do. The CB is only 14" wide even though it's about 5 feet long when deployed. There is still a huge gap between the hull and the CB which allows water to swoosh in between the hull and the CB providing no resistance.

The posts I've read regarding weighted CBs indicate that there was not a significant performance difference close hauled. The major result of those mods was a reduction in the heeling of the vessel.

There was also a discussion about mounting a small fin to the hull/CB for better motoring/steering performance. I think that my board lowered 2-4 inches will provide good results when motoring (like on rails, I hope)

I was really surprised how light the CB is in the water. My board is 65lbs but in the water I can hold it up with one finger. I may need a way to hold the board down. I'll be posting some pics soon.

Gerald, I understand the objective for motoring. I would guess it will be very effective in holding a track under power. However it seems to me it will be a big detriment for sailing.

Long-keeled sailboats generally carry 40% of the vessel weight down there, helping deter excess heeling caused by their long water dams. Yours will deter side slipping, a long water dam, but will have no deep weight to counter heeling. My guess is that the long keel will cause immediate heeling right to the 50 degrees range, at which point the board escapes the surface.

ON the positive note, the boat shouldn't suffer ANY weatherhelm at all ... with that long keel it won't matter what sails are up, it will just track to the rudders until the board loses its bite. I'll be very interested to hear your results ... and I hope I'm wrong~!

Frank C,

I didn't think of the weather helm issue. I'll make a note of it. What would be other ways to test for effect?

I think it will eliminate all weatherhelm - a good thing. You needn't check for it. I'm worried that it will greatly exacerbate heeling, to a point of discomfort. I'd say you should choose a day with light winds, maybe 8 to 10 knots wd be ideal.

Since you have both sails on furlers, I suggest starting out your saiing tests with just bare traces of canvas unfurled .. both foresail and mainsail. Then gradually pull out a bit more main and maybe a third of the jib. If you're liking the hull's behavior, now try increasing the mainsail, carefully until it's out to full size.

Normally a full main with very small jib can cause ever increasing weatherhelm, but I doubt you'll find ANY weatherhelm. Your long board should eliminate that problem. As mentioned above, I think the boat will heel too much, even in light winds. Then as the short depth of board gets lifted by heeling, the hull might just skid leeward.
Proceed cautiously ... in fair winds ... best of luck.

I don't know if this is true.

Someone told me that if you have one 18hp OB you get 18hp. The second 18hp OB adds only half its power to the total. So, he said, two 18s produce 27hp. What's up with that?

I don't like to miss an opportunity to post this pic.

A machanical genius told me that even if I had three 18hp outboard motors I would still have only 18hp. I would gain lots of low end torque but no speed beyond that prvided by 18hp's.

heheheheh..

Thankfully, all the technicians and engineers don't know any better.....

A machanical genius told me that even if I had three 18hp outboard motors I would still have only 18hp.

While you would likely not get 3x18 or 54hp, since they are working in parallel, you would effectively get over 18 - think three people pushing a car out of the sand vs one. The limiting factor would be the props ablility to cut through the water and with the supplimental torque it could be changed but prop size and blade angle are to much for me on a Friday lunch.