Swapped my 50HP 2-srtoke for a 30HP 4-stroke

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Glorious
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Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by Glorious »

I have a 26X and I recently swapped my 50HP 2-stroke for a 30HP 4-stroke. I did this because the 30HP 4-stroke is quieter, much better fuel economy, Less smelly, Still plains so I can drain the ballast although if I have more than 1 guest I have to drop them off to make it easier to drain the ballast. It's fine with just the misses and me. Much smoother and easier to manoeuvre inside the marina.
The 30HP Tohatsu (Nissan) is 4 years old. The 50Hp Nissan is 11 years old.
I am not experienced enough to know if the lighter engine has any effect on the sailing characteristics of the boat. I would expect that it would improve the boats performance by being a bit lighter however the stern of the boat may have come out of the water a bit.
Has anyone else had any experience with this sort of thing?
Kelly Hanson East
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by Kelly Hanson East »

There are a couple of threads about using smaller motors - the weight and balance has to help you of course. Im not a good enough sailor to see the difference though.. :?

The times I have thought of cruising the NY canal system (10 mph speed limit)) a smaller motor makes a lot more sense - even just a 9.9 HP
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Rick Westlake
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by Rick Westlake »

When I bought my Mac 19, the previous owner kept the engine. I powered it with a Tohatsu 9.9, which was not enough engine to dump its ballast with power alone. (I did find I could "blow my ballast" with an electric inflator pump, if I needed to, but it was just a trick for me.) But it was perfect for my needs - getting out of harbor and up to open waters for sailing.

Bossa Nova has its original 50 hp Honda, which moves me at harbor speeds running 1500-2000 RPM. But a 9.9 Tohatsu would do all I ask of an engine, 95% of the time.

I think you made a smart move with the 30 hp Tohatsu.
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MadMacX
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by MadMacX »

Glorious, my X came with a High Thrust (?) Yamaha 25 HP 4 stroke and while it is quiet and trouble free, it is also rather slow. My top speed is 7.1 knots (GPS), but I usually cruise at approx. 6 kph. I'd be curious to hear what kind of top speed you get with your 30 HP engine.

I used to be concerned with how slow it was, but now that I also own a powerboat, I can use the powerboat on longer trips, or when we have friends along. My X is now used primarily for sailing, which I like. :wink:

Please let us know how the 30 HP engine works out for you.

Pat
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c130king
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by c130king »

Something that may help the smaller HP engines is a Powerthruster.

I have one on my 40HP 2-Stroke and I seem to get speeds as fast as many claim for their 50HP engines. But I am not sure exactly how good it is because it came with my boat.

But I feel pretty confident that it is good for a couple of knots.

Just something to consider.

Cheers,
Jim
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Duane Dunn, Allegro
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by Duane Dunn, Allegro »

Most 40hp and 50hp motors in a given brand are actually the exact same motor so you should get nearly the same performance with them. The only difference is at the top end, usually a higher rpm target.

The 25hp to 30 hp range seems like it would be a perfect choice for those who want small, quiet, efficient motors yet want to gain a few of the benefits that make a Mac different from a typical small sailboat. A 9.9 gives you none of these, it just gives you a boat under power that is the same as any sailboat yet is a slower boat under sail than almost any other sailboat. (I know there are those who argue the mac can sail fast, but you need to look no further than it's PHRF rating to know this is not true.)

You don't need to get on a plane to dump ballast, actually that would defeat the goal, you simply need to get to a bow high attitude so the water will drain. This is not a plane, you have not climbed out of the hole past the bow wave. A 25hp to 30hp motor is perfect for this. Still you don't get all the Mac advantages, you won't be out running any storm systems at 15-20 knots or blasting through contrary currents with ease.

I notice that I gain almost a knot of speed under sail or power when I get more weight forward. Sending a person to the vee berth for a nap gives me an instant speed increase. You should get the same effect by removing weight from the stern. This motor change should bring your speeds up across the board.
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AlaskaMan
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by AlaskaMan »

Mental Floss has the 30hp NISSAN and I've had no problems running with it.
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by DownSouth »

Duane Dunn, Allegro wrote: Sat Oct 03, 2009 12:41 pm A 9.9 gives you none of these, it just gives you a boat under power that is the same as any sailboat yet is a slower boat under sail than almost any other sailboat. (I know there are those who argue the mac can sail fast, but you need to look no further than its PHRF rating to know this is not true.
I am considering getting rid of the 23 year old Honda 50hp for a Yamaha High Thrust 9.9hp motor on our 26X. It will easily get the boat to hull speed in all but the worst conditions when you would unlikely to want to do 6knots anyway.

Yes it will be the same under speed as many trailerable sailboats the same length (and most are shorter, and slower as a result) but I have not found another sailboat that is fibreglass, has water ballast (so light enough for a reasonable vehicle to tow), that has anywhere near the volume of space, private head, and head room that the MacGregor power sailers have. I have owned ‘better’ sailing boats that were shorter and when loaded with the required gear for a week afloat sailed no faster than our Mac……

Down South
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rsvpasap
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by rsvpasap »

I just want to give a vote of support for this idea. I switched my Suzuki 60 (which had a blown head gasket at 1400 hours) and 6 hp kicker for a 20 and a 9.9.
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Ixneigh
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by Ixneigh »

Some of my most memorable days were places like this:

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And there’s no “fast boat” that’s getting me there except maybe a hobi cat. And that doesn’t have a cabin.
"Shoal Idea"
2011 M, white
Etec 60
South Fl.
DownSouth
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by DownSouth »

rsvpasap wrote: Wed Oct 30, 2024 8:54 pm I just want to give a vote of support for this idea. I switched my Suzuki 60 (which had a blown head gasket at 1400 hours) and 6 hp kicker for a 20 and a 9.9.
Image
How does it go with your new motors? Is the 9.9 a high thrust type?

Regards

DownSouth
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rsvpasap
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by rsvpasap »

I'm not necessarily trying to endorse any particular brand of outboard motor. This is a Suzuki DF9.9BEL5. Unexpectedly quiet at 6 knots, high displacement (it's essentially a detuned 20, same footprint), 12 amp alternator, electric start.

The only brand of 9.9 outboard I'm aware of that calls itself "high thrust" due to its gearing ratio is the Yamaha which has a displacement of 212 cc. The Suzuki has a displacement of 327 cc.

I want something that gets excellent gas mileage for long distances at 6 knots, giving me maximum range. I also tend to frequently motor-sail in light winds. So far this seems to totally match.
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Re: Swapped my 50HP 2-srtoke for a 30HP 4-stroke

Post by DownSouth »

Yes that is what I was looking for maximum range. I realised it was a Suzuki after looking a bit more closely!

Do you have waves/swell or tide where you sail? How effective is the 9.9 at pushing into wind etc.

Thanks for your pictures and advice.

DownSouth
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