Outboard Motors......

[Swift]

Hi All

Mark's comment about the benefits of having a 250KG inboard down below reminds me, does anybody know if boats built for outboards have more compensating ballast ?

My Mk1 has lead bars under the toilet floor and the sink cupboard and I presume that they must be to balance the weight of the transom mounted outboard. Later model Mk 2 & 3 boats with outboard wells in the cockpit which moves the outboard weight slightly further forward and lower, so maybe they don't require the additional ballast ?

Anyway, judging by the size of the lead bars they would only be maybe 50KG which combined with a 25kg outboard leaves the boat 175 KG lighter than one fitted with a 250KG inboard. That would translate into more than a half inch of extra freeboard (and maybe less righting moment) unless of course extra ballast is in the keel?

Cheers
Keith

[storm petrel]

Hi Keith,

The 250 kg includes the 60 litre fuel tank on Storm Petrel. I did notice at the recent regatta that she sits at least an inch lower than the Tophats fitted with outboards (though their water tanks may also have been empty while mine was pretty full). This seemed to have little affect as at the regatta I only noticed a difference in boat speed when the wind eased and my prop drag came into play.

There was an earlier post on maximising the speed of Tophats for racing and it suggested that keeping them light and ensuring the weight ditribution is forward and low is the key to keeping them sailing fast on their lines.

Cheers,
Mark

[Dolphin]

G'Day Keith and Mark.
On Felicite I have a diesel and there are 3 or 4 lead bars in the V Berth in a section further forward of the locker under the cushions, thats about as far forward as you can go. I found also that the bars were'nt held in so I ran some fibre glass over them as they are just sitting on the hull. I would have thought that the galley area would have been pretty close to the centre of gravity and as such wouldn't have much effect on the trim.

She does float low in the water but that is a combination of the amount of good stuff on board. Maybe that's why I've ran aground 33 times? Nah, its just because I was in Port Hacking.

All the best, Greg.

[Phillip]

Evening All,

I removed the lead in the bow of my Mk1, and placed a port-a-potty and 30m of anchor chain in
place of the weigth (about equal). Sold the lead for a lenght of heavy chain for my mooring

I have noticed that the bow of SEAKA is slightly up, but hope to bring it down once I load cruising gear.
I didn't like the idea of several lead bars running around inside in the event of a knock down.

Would be interesting to hear if those who have cruised overseas removed the lead in their Mk1's.

I think the extra lead to be found in Mk1's is a solution for a stiffness problem the racers identified that is anwsered in the Mk2 & 3 which have MORE lead in their keels! Look at the displacement weights Mk 1's are 2.54 tons, Mk 2 & 3's are higher (Couldn't find the figure while on line)

Keeping the bow down increases the waterline length, hense more speed

Phillip
SEAKA

[Swift]

Hi Phillip

Thanks for the information. I just got around to checking the specification I have on file. The MK 1 brochure from Fibreglass Yacht Sales at Monavale list the displacement at 2.54 Tons with 2,500lbs ballast. A brochure for the Mk 3 list the displacement of 2.58 Tonnes and 1234 KG ballast. One Tonne is 0.98420653 Tons so the displacement is the same. However converting the KG for the ballast to pounds reveals that the M3 (and presumably the Mk 2) has an extra 221 pound of ballast.

If this is correct then later boats must be lighter with a slightly improved ballast ratio. This is not what I expected because the later models were laid up with chopper guns which results in a higher resin to glass mix and therefore a heavier hull to obtain the same strength. I suppose some weight was saved in the re-design of the cabin and maybe generally improved engineering.

Just to confuse things a bit the Top Hat Mk 3 review in Australian Sea Spray in October 1980 provides the following figures: displacement 2743 KG, ballast, 1292KG. This is large difference in displacement of 359 lbs compared to the Mk 1 and all but 10 pounds of this is ballast. Also the same article mentions that the inboard models are fitted with a lighter Spanish made diesel which weighs only 88KG. So it's hard to say if the difference is in the later models is 221Lbs or 349 Lbs of additional ballast, or maybe the models with the lighter diesels had even more additional ballast?

The lead bars in my My 1 are solidly bolted in place and will be a bugger to get out. But one day..... maybe I will buy that barrel of chain I have always wanted so I can have a completely self storing rode, so then the bars will then have to come out.

Cheers
Keith

[storm petrel]

Hi Keith,

Very interesting numbers. I wonder if anyone else on the site has the exact figures for the displacement and ballast of the Mks? Has anyone still got the original documents for their boat?

It would be nice to get the bottom of this.

Cheers,
Mark
Storm Petrel(Mk11)

[scotty]

Hi

I bought a new engine last year upgrading my old 1998 8hp Tohatsu 2 stroke long leg (very reliable) with a new 9.8 hp Tohatsu 2 stroke. I found that the dimensions and weight of the 9.8 were the same as my old engine. I am very pleased to have the extra power as I often find myself going to windward in 20kts!

I stuck with Tohatsu because my pride and joy swings on a buoy and the old engine was not flushed for 8 years without major issues (although during that time the thermostat was replaced). It was still going when I sold it. I am hoping to get 10 years out of the 9.8!

Good luck with your choice.

[ozzibod]

G'day Scotty
Thanks for your input. I am leaning towards getting an 8 hp 2stroke longshaft Tohatsu myself. I understand that they are much more economical than the 1993 or so model 8hp 2stroke Evinrudes which I am am told are a cross flow motor and run very smothly but rather hungry. Being US designed there was probably not so much consideration devoted to fuel economy. The Tohatsus are I believe a loop scavenged motor and being Japanese designed, more frugal with the fuel. I beleive they dont run a smoothly as the old Evinrudes but I am looking for fuel economy as well as ease of maintenance and mechanical simplicity.
Thanks for your two bob's worth Scotty and also a big thank you to all other posters. Your views have enlightened me enormously.

Cheers
Austin

[Miker]

Austin, if you can use the 4 stroke you'll be a little better off fuel wise and for ease of use. I burn a litre an hour on 3/4 throttle. The downside is, that mine didn't fit in the well, so is on a transom bracket/lift.

Michael