Engine Size (20hp or 10HP)

Posts about mechanical systems on a Telstar, including the outboard engine.

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Engine Size (20hp or 10HP)

Postby vancouver » Wed Mar 06, 2013 8:40 pm

I am thinking of re-powering and reducing from the 50hp I have. Primary considerations are full economy and weight. Has anyone used a 9.9 hp on the Telstar 28 or have thoughts on it. I will be satisfied with a cruise of 5 to 6 knots.
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Re: Engine Size (20hp or 10HP)

Postby Gene » Thu Mar 07, 2013 12:02 am

I think you'll find the weight difference between a 9.9 vs. 20 hp to be negligible. I "think" Tony had chosen the 20 so that he could get power tilt, electric start & alternator. I don't know if you can find that in a 9.9hp still? If I ever need a new motor I'd definitely opt for the 20 instead for the weight savings & ability to pull start if needed.
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Re: Engine Size (20hp or 10HP)

Postby Gene » Thu Mar 07, 2013 12:10 am

I stand corrected, Defender does list a 9.9 Honda with long shaft, alternator, power tilt, etc. That said, again the weight difference is minimal, not a big $$ saving either. I'd look to see how alternator output compares...
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Re: Engine Size (20hp or 10HP)

Postby vancouver » Thu Mar 07, 2013 2:23 am

Actually Honda and Toshia both make a 9.9 with long shaft, power tilt, and remote. Honda has a 12amp alternator, toshiba has a 6 amp. With the weight difference, I could carry my Honda 2000 generator for charging when cruising.

I was interested in thoughts on the 9.9 ability to move the boat at 6 knots.
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Re: Engine Size (20hp or 10HP)

Postby Gene » Thu Mar 07, 2013 4:57 am

I would think in calm seas it would do fine... but there may be times the extra oomph comes in handy? I don't really see any downsides to the 20, do you? Perhaps some of the existing 20hp guys will chime in and give you some actual feedback on that...
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Re: Engine Size (20hp or 10HP)

Postby Ron » Thu Mar 07, 2013 12:21 pm

I had a Honda 9.9 on a 25 foot wing keel Catalina. It was capable of moving this significantly heavier monohull at 6 knots, but the three Telstar hulls may use up a little more of its power. I'd be most concerned how the various remotes compare to your existing 50hp version. Having to operate or tilt any of these outboards by reaching way back there would not be acceptable to me. The difference in weight is only around 10 to 15 pounds. The 15hp motor is actually a detuned 20, so you can ignore it. Make sure you order either one with the power thrust configuration (with more thrust from a lower pitch larger blade propeller). I can get my 20hp with the 10x7 5/8 prop up to 8 knots or so. My 9.9, also with this prop, could barely break 6 knots on the heavier boat. Note that the two motors use the same prop.

Toshiba makes an 9.9 hp outboard?
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Re: Engine Size (20hp or 10HP)

Postby vancouver » Thu Mar 07, 2013 3:16 pm

OOPS. That is a Tohatsu, seems I wasn't awake during that post. It is a 9.8. The dealer has a one an XL shaft with remote, high thrust, and power tilt. Been on his floor since last summer and eager to sell. It weights a a bit over 80 pounds. Biggest prop it can take is 9.25.
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Re: Engine Size (20hp or 10HP)

Postby Ron » Fri Mar 08, 2013 1:40 am

If the Tohatsu 9.8 is a good deal, it might turn out to be OK. The Honda 20 has got to be a lot more. The XL shaft would put it lower in the water than the Honda L's. That's both good and bad. Lower would stop some of the cavitation in choppy water, but you may not be able to get the prop totally out of the water when lifted and tilted. How does its degree of tilt compare with the Honda's? If it's significantly less you better take some measurements first. You may be able to get a 10 inch aftermarket prop to fit. The standard prop on the Honda 20 is something like 9.5 x 10 pitch. Solas may make something that could work on the Tohatsu.

One question - I thought that the water currents, both tidal and river oriented, in your neck of the world are significant. The 9.8 might not be able to handle it if that's true.
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Re: Engine Size (20hp or 10HP)

Postby Gene » Fri Mar 08, 2013 2:27 am

As with everything in life, it is a $$$ question. 20hp is the expensive "safe play." Maybe the 9.9 Tohatsu is worth it? By all means, let us know!!! :D
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Re: Engine Size (20hp or 10HP)

Postby escape » Sat Mar 09, 2013 5:25 am

Personally I would not go below 20 hp. It is always better to have a bit more power than not enough and a 9.9 hp is barely enough. It will be ok in calm water and soft winds. My T28 came with a Tohatsu 20 hp with the standard 3 blade propeller a 9.2" x 9 pitch. Although I could get past hull speed I had the feeling that the propeller was “spinning”, so I bought a high thrust propeller 4 blades 10" x 7 pitch. Can’t wait to try it out, I should get better speed at slightly lower rpm and steadier speed going against the wind and waves as it was the case with my previous boat. It was a trailerable C&C Mega 30 with a 9.9 Honda high thrust 4 blades propeller. The C&C is slightly heavier that the T28 and many time I wished I had more power. Of course this also depends when and where you cruse your boat. If you only need the motor to get in and out of the dock or mooring then 9.9 hp would be ok.
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