Changing from 50 to 20 HP

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

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Changing from 50 to 20 HP

Postby Live4sea » Mon Nov 02, 2015 3:35 am

I have a 2007 Telstar 28 with a 50 HP engine. I got it used and have been concerned that the 50 hp is heavier than I would like ever since I got the boat a few years ago.

Last year I replaced the water pump on the 50 hp. This year, the lower unit has deterioration on both sides of the gear casing and it is not holding pressure, so the marina engine conractor is recommending that the lower unit be replaced for around $1,300.

Rather than continuing to spend money rebuilding an old engine, I am considering switching to a new 20 hp, which I have seen for around $3,900. Of course, I assume I will also need to get a new side control panel for the 20 Hp, and perhaps other parts or accessories for it, which will increase the cost. Do any of you have any experience or suggestions about making that switch from a 50 to a 20 hp? Did you replace the side mounted control panel, 15 amp charger, tachcometer and other parts at the same time. Any tips or insights into the pros and cons of making that switch would be greatly appreciated.
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Re: Changing from 50 to 20 HP

Postby vancouver » Mon Nov 02, 2015 6:58 am

I changed my 50 for a 20hp Tohatsu. Very happy with the result. It has a 12amp alternator same as the 50 so no loss there. You will have to purchase a new remote. You should be able to use all the customized linkage hardware to hook the 20 up. It will require a little rework on the mounting to the outboard box, but nothing to difficult. The stock propeller didn't work to well. I traded it out for a lower pitch 4 blade. WOT gives me 8 knots. At 6 knots, it uses 1/3 the fuel that the 50 did. Also happy with the 100 less pounds.
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Re: Changing from 50 to 20 HP

Postby Bill » Tue Mar 15, 2016 7:37 pm

I'm leaning toward a Suzuki 20 hp, the newer model with electronic fuel ignition. Owners report great fuel efficiency, lack of problems with fuel, also lightest, and possibly cheapest of the 20 hp motors available. Now available with power tilt. Anybody out there try one on a T2?
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Re: Changing from 50 to 20 HP

Postby jannpage » Tue May 03, 2016 11:10 am

Greetings. Have you gotten your new engine? I just took delivery of a 2016 Suzuki 25 hp and hope to remove my old 20 hp Honda today.. I chose the Suzuki because of the fuel injection and I upped to 25 hp for several reasons. I run a long, narrow, shallow and twisted inlet to the bay. It is also on the west side of the bay so it always has a bit more wind on my stern as I come home than I would like. I have learned that with light multi-hulls in shallow water backing power is critical. The Telstar has a lot of windage. The moment you slow donw to a crawl, the boat wants to weather vane with the bow dead downwind. Particularly when the keel is up ( for shallow water). I love and respect Yamaha's HO engines for this reason, but they still do not have fuel injection and fighting carborator's and ethanol is just to big a hassle for this old man so I decided a 25 would give me a bit more backing down power. I still hope to find a big blade prop and perhaps a way to get rid of the exhaust bubble.

With my first look at this engine and I am in love. I hope that love will last.

So I will be interested in how you like your new engine. If you use it in Salt Water, I suspect flushing is sill critically important . At least, I intend to flush mine carefully every time I use it.

Good luck.
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Re: Changing from 50 to 20 HP

Postby Bill » Tue May 17, 2016 5:42 pm

I have the Suzuki 20, but have not run it yet. In the process of changing out from the Honda 50, I discovered water in the wood core of the motor mount. I've drilled it and am drying it out, will treat with penetrating epoxy, also will create solid epoxy cylinder where new mounting bolts will go. Not really a big problem, the skins seem pretty thick, I bet lots of boats have water there without it bothering anything- yet. The vertical pipe that the motor mount rides up and down on had an issue as well. The manufacturer managed to grind all the way through the weld at the top and bottom, on the side facing the fiberglass motor mount. I removed mine to clean up corrosion where it mounts, felt water inside. Drilled a hole in bottom to let out about 3 oz water (difficult to drill). It is now with a welder.

The only issue I have with the Suzuki was that the dipstick was near impossible to remove, I have modified it some. Otherwise looks like a good motor. Will report whenever I finally get the boat in the water (fixing a number of things).
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Re: Changing from 50 to 20 HP

Postby Bill » Mon Aug 08, 2016 2:12 am

I have been using the 20 HP Suzuki for 2 months now, no complaints, runs fine. I don't have a tach hooked up, so I don't know if I really have the right pitch prop, I don't think I've ever been close to WOT, plenty of power. Only just now got the knot meter running, not sure how fast I typically run, feels like about 6 kts if I'm trying to make tracks. Mostly I'm running slow through the anchorage, and real slow so I can douse sails and retract in protected water on my way back in. It came with a stock 9 1/4"diam x 9" pitch prop, as I recall. Could be I'd have been ok with a 10 hp, but this only weighs 121#, doubt the 10 would be much lighter, and I expect I have more reverse power, should I need it some day (I'm on a mooring, don't use reverse much). We will see how it holds up. Will only get a fresh water flush once a year, when I haul it. Anybody looking for a 50 HP Honda that needs lower end work? Didn't think so.
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Re: Changing from 50 to 20 HP

Postby jannpage » Fri Sep 08, 2017 10:47 pm

When re-powering an outboard powered sailing vessel I always pay a lot of attention to backing up power. Understand I am not talking about horsepower but the engines ability to move lots of water when in reverse. Particularly if you sail in really shallow water.
I do most of my sailing in the shallow waters of NW Florida. Even getting in and out of my slip and to open water involves over a mile of more of narrow twisting channels with little room for error. So I run pretty slow to avoid bottoming at speed and getting really stuck on deep and soft mud. The slow speed limits the boast responsiveness to steering while making it more vulnerable to the wind or touching an ama on the edge of the channal and grounding me. And if I am grounded, the odds are I need to back out against the wind.There are at least 3 major problems that restrict the backing up power of outboard engines.
1`. Prop. The standard outboard prop is made to go forward at speed. Even a 10 hp will push a light boat at speeds unthinkable for a sailboat. They have a small blade area and fairly high pitch and made to let the engine turn to develop full power. Changing the prop can help, but you quickly learn the engine is not geared to swing a large prop or a prop with lots of area.
2. Exhaust gasses cause props to cavitate in reverse. Thru the prop exhaust helps forward power but limits prop grip on the water in reverse.
3. Many engines have only limited throttle in reverse.
I use Yamaha HO engines as a measuring stick against which I measure all other engines for use on a light, shallow draft boat with a lot of windage. Talk to a Yamaha dealer about their HO engines and learn what they have done to build a sailboat engine and then compare what yo learn with other. I have been disappointed over and over. So far I find no real competition except price. but if enough of us learn what er need, perhaps we will see some other builders really build a sailboat motor that will back up with authority.
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Re: Changing from 50 to 20 HP

Postby escape » Sun Sep 10, 2017 12:43 am

I am using a 4 blades Solas 10x7 on my Tohatsu MFS20 and it make's a huge difference, I get a lot more backup power and more forward speed at lower rpm.
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Re: Changing from 50 to 20 HP

Postby vancouver » Mon Sep 11, 2017 7:57 pm

I have a Tohatsu 20hp and changed the stock propeller to their 4 blade 10x7. Very happy with that configuration. I usually cruise at 5+ knots with good fuel economy. But it is capable of drive the boat into 20 knot winds and 3 foot seas at 5 knots, although the fuel use doubles. It calm water will deliver 8 knots. Plenty of drive in the marina in both forward and reverse.
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