outboard engine size

Talk about the older Telstar 26 and 8M
john W-E
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outboard engine size

Post by john W-E »

I have an 8 meter telstar that looks as though it will require repowering, due to the age of my 15hp two stroke yamaha. I am recieving contradictory information about what sized engine is required. The yamaha dealer is recomending a 10hp motor with a standard gearbox and a high thrust prop. ( he says the weight of the boat does not require the high thrust gearbox) The toyhatsu dealer thinks that a 6hp sail drive outboard would be more than adaquate. Financialy this is half the price, in fact I could have a pair for less than the 10hp yamaha and at 25kg each not much weight penalty. with all the benefits of a twin engines.
I would be very gratefull for any first hand information on what is the right size of engine. I tend to sail in areas with strong tides, I am taking the boat to the outer hebradies next year so require good fuel economy( better than my old two stroke)
John
Ron
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outboard engine size

Post by Ron »

John -

I've got a newer 28, so this may be comparing apples with oranges. The 28 comes with a 20 hp Honda and has an optional 50 hp available. The latter is definitely overkill, the former is probably not. My 28 weighs close to 4500 pounds, but that includes a head with holding tank, 2 sinks, water tank, 2 burner propane range with broiler, refrigerator, mast lowering system, the Honda 20, a fairly heavy ama folding system, 4 sails, etc. If your boat weighs anything like the newer ones, you'll need at least 15 hp to move it adequately in any sort of current. Less and maybe you can do with a 9.9. I would not go any smaller though. I had a 1,000+ pound heavier wing keel Catalina 250 a few years ago which worked very nicely with a Honda 9.9. No keel, but the Telstars 3 hulls could be a little more difficult to move in the water though.
Ron Marcuse
Telstar 28 #359 "Tri-Power"
john W-E
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outboard engine size

Post by john W-E »

ron
many thanks.
john
JoeWalling
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outboard engine size

Post by JoeWalling »

Hi John

I have a 2 stroke Yamaha 8hp with a big prop. I find this pushs the boat along very well, its just that it gets a bit noisy at the higher end of the rev band. My ideal would be a 10hp 4 stroke - I would not go higher than that. I'd also definitely go for an extra long shaft as my long shaft quite often sees daylight in choppy water. I have a Mark2, by the way,which I believe is the lightest of the older models.

Joe
Ron
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outboard engine size

Post by Ron »

Assuming that it's not shaped like a brick and the hull / prop is not totally fouled, the boats displacement is probably the single most important factor when picking a motor out - but the footprint and total wetted surface of the 3 hulls on a trimaran adds something to the equation as well. Has anybody actually weighed the three older boats - Mark I, Mark II, and 8M? Tony was off by about 1,000 pounds on the 28's specs (3,500 brochure vs nearly 4,500 on a certified truck scale). I wouldn't believe his earlier attempts at weight either. By the way, this is not a Tony Smith thing - just about every builder is off by a large margin.

Didn't one of them come with a 28 hp Jet drive? Why did this version have 28 hp and some of the others work with an 8? Another thing to think about - most 8 hp motors share their configuration with the 9.9 model. Same weight, different carburetor. Like getting an extra 2 ponies for free. And definitely go with a high torque or high thrust prop if available. This is not a 500 pound dinghy.
Ron Marcuse
Telstar 28 #359 "Tri-Power"
luigisante
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outboard engine size

Post by luigisante »

The motor of choice for the older Telstars has been the Yammaha 4 stroke, high thrust "HO", 3-1 gear reduction, 9.9 h.p. This motor cruises the boat, fully loaded, at roughly 5-6 knots at a consumption of .37 gph. It can probably top out at 7 knots. Because of the gear reduction and larger prop, it can deliver its massive torque in any seaway. Thus, you get a true 5-6 crusing speed and a bit more power if you need to fight an opposing tide at the mouth of a bay or something.

The engine is also incredibly reliable. I think the 9.9 is actually a detuned 15 hp. At least, that is my recollection.

Lou Giansante
Mark I
Hull #52
Ron
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outboard engine size

Post by Ron »

luigisante wrote:The engine is also incredibly reliable. I think the 9.9 is actually a detuned 15 hp. At least, that is my recollection.
Lou -

I think the 15 and 20 hp motors share the same block, likewise for the 8 and 9.9. Just about every manufacturer does it the same way. The difference is in carburetion and other sub-systems. Sort of pays to get the more powerfull of each pair (in terms of weight, etc.). Depending on the boat's actual displacement (not necessarily the adverstised specs), the 9.9 could be a good choice. At 4300 to 4500 actual pounds, the 28 might be heavier.
Ron Marcuse
Telstar 28 #359 "Tri-Power"
ajaxpc
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outboard engine size

Post by ajaxpc »

I bought a new Yamaha 9.9 high thrust, extra long shaft, last year. I got the electric start plus remote control version.

This is a really great engine. It drives the boat comfortably at 5 - 6 knots. I think I use a little less than 2.5 litres per hour, which is higher than I've seen quote elsewhere but maybe I'm a bit heavily loaded ...

I've also had some long runs with it, running the engine for several hours at a time. It's a quiet engine, and it puts 6amps into the batteries at this speed.

The electric start is a nice extra, given the awkward position of the engine and the extra tug needed to start a 4 stroke. The remotes mean I can drive the boat from the cockpit without leaning over the stern to adjust the throttle or change gear.

I had a Mariner 8hp 2-stroke before, which really didn't do the trick. It drove the boat OK in smooth water (5 knots) but was very slow in a chop (3 knots, occasionally less). It also sometimes didn't lock down properly when I went astern - this cost me a couple of grp repairs.

My local boatyard is a Mercury dealership, and when I told them I was buying the Yam 9.9 they said I was making the right choice ...##

Also - I was told by another boatyard, for what it's worth, that the 9.9 was a modified 15 not an uprated 8.
Ron
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outboard engine size

Post by Ron »

ajaxpc wrote:Also - I was told by another boatyard, for what it's worth, that the 9.9 was a modified 15 not an uprated 8.
Look at the Yamaha website. The specs list the 8 and 9.9 as the exact same size (cc's), with the 15 and 20 being very close (but not exctly the same). I'd guess that the 20 has a slightly longer stroke than the 15.
Ron Marcuse
Telstar 28 #359 "Tri-Power"
ajaxpc
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outboard engine size

Post by ajaxpc »

8 & 9.9 - I'm obviously too trusting!

The context was odd - the yard was selling what they claimed was a 9.9 high thrust, but it had a large '15' decal on the side of it. Their story behind this was that it had been bought with a loan or a grant directed at small inshore fishermen, and that the smallest engine the grant would support was 15 hp.

I didn't buy the engine, but obviously bought too much of the story ...
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