F2.5 LMHB, 4 stroke 2.5hp Long shaft as an emergency kicker for 16ft boat

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OKBoater

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F2.5 LMHB, 4 stroke 2.5hp Long shaft
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Will it get me back to the marina with a 16ft boat like this one?
(Lakes only)

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These are the specs for the motor.

https://www.yamaha-motor.ca/products/details-build-price.php?model=4744&group=OB&catId=82
 
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I had a Mariner 4hp 4 stroke on my old 17’ dory. Gave around 5 knots full throttle, you wouldn’t really want any less if there is any wind/tide around.
 
If its only use is as an emergency motor then go for a larger hp, either 3.5 or 4. if you want to also use it on other boats then a long shaft will not be suitable for most small boats.
 
rustybarge said:
Why not get the 3.5hp Tohatsu/mercury which is cheaper and has a 85cc engine.

Just part exchanged my Yamaha 2.5 for a 3.5 which I have on a 13' Dory, so I'll let your know in the next few days what sort of speed I get.
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Did you try the 2.5 and if so how did it perform?


Glenlivet said:
I had a Mariner 4hp 4 stroke on my old 17’ dory. Gave around 5 knots full throttle, you wouldn’t really want any less if there is any wind/tide around.
Click to expand...

Tranona said:
If its only use is as an emergency motor then go for a larger hp, either 3.5 or 4. if you want to also use it on other boats then a long shaft will not be suitable for most small boats.
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I want to go as light as possible, and the 2.5 is only 38 lbs, and I want to get a long shaft because my next boat will be larger. I have read that 2.5's can be used to bring back sail boats...I'm not concerned with speed, as long as it gets me home versus rowing.

Here is a video of a 2.5 Suzuki pushing pushing 17 ft boat in strong tides.
https://www.youtube.com/watch?v=8qoo1LqImd8
 
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OKBoater said:
Did you try the 2.5 and if so how did it perform?






I want to go as light as possible, and the 2.5 is only 38 lbs, and I want to get a long shaft because my next boat will be larger. I have read that 2.5's can be used to bring back sail boats...I'm not concerned with speed, as long as it gets me home versus rowing.

Here is a video of a 2.5 Suzuki pushing pushing 17 ft boat in strong tides.
https://www.youtube.com/watch?v=8qoo1LqImd8
Click to expand...

The ultimate light weight ob that I've had is the ultra long shaft 6hp Tohatsu saildrive: it pushed my little 25' one ton cat into strong winds and chop no problem.

Slightly more at about £1k, but you will get a guaranteed result!
 
In a lake? Yes it will get you back no problem. Only issue I can see is steerage in wind. The aux will be significantly offset and in certain conditions turning into the nearside (side the aux is on) bow or holding the bow in the wind may be difficult in some conditions but it will happily push you regardless even if it's slow off the start. I would not be quite so positive in any sort of tidal current though if you take her to sea
 
BruceK said:
In a lake? Yes it will get you back no problem. Only issue I can see is steerage in wind. The aux will be significantly offset and in certain conditions turning into the nearside (side the aux is on) bow or holding the bow in the wind may be difficult in some conditions but it will happily push you regardless even if it's slow off the start. I would not be quite so positive in any sort of tidal current though if you take her to sea
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I was thinking of having some sort of tiebar setup that I could hookup to the main if necessary to assist steering. Anyway I am confident it will be enough for the lake...here is a video of a 2.5 pushing a 17ft boat.

"We put a 2 1/2 4 stroke Suzuki on our 17 foot ODay Daysailer in 2015 and it pushes it to hull speed at 1/3 throttle. The hull weighs 700 pounds. Also because of the slope in the transom we can hang it on the right edge of the starboard transom and the prop sits below the hull, so we can turn it 360 as needed. The Suzuki has forward and neutral.

Check out the video, we had a 8-10 knot headwind, just below whitecapping on the Bay, so I am confident we will make decent headway against a 3-4 knot current."

https://www.facebook.com/129769927103126/videos/940392169374227/
 
A sailboat produces far less resistance in the water. Here is a vid of mine from many years ago going against a headwind and a 2knt current in a similar size boat. Note the aux pushing is a 8hp but on about 1/4 or less throttle. Any more was just wasted power without producing any more speed. What an 8 does give though is more torque which aided getting going and manoeuvring. I found the hull speed no matter what you did with the throttle was about 4.2 knts


edited to add, the 8 gave the ability to handle a quartering sea, it's that point that I may have some reservations on a 2.5 at sea. The torque to make concise adjustments to direction etc. The 2.5 will push you to hull speed but has it got the torque to punch against waves and maintain that hull speed that is questionable. On a lake I believe you will be fine, certain sea conditions, perhaps not.
 
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It will do it- but try and get the Sailpower version (if they do one) it will have a larger prop with lower pitch and will provide much more thrust for a given power output.

Yamaha, Mercury, Tohatsu all do them, but some don't start to higher outputs.

If it's a standard outboard, try and get a high thrust propellor for it....
 
It will depend of the laden weight of your boat and the hull design (planning vs displacement).
My Marina 16 GT used to be powered by a Mercury 9.9hp four stoke, which weighs 38kg, and with 6 adults on board, no wind and at flat calm water on the Solent we were making exactly 6 knots (7mph)...So don't expect to get more than a couple of knots with a 2.5hp...Whilst that may be fine on a lake in perfect conditions, on the sea, where you might be trying to limp home against the tide, if you are against a 2 knot tide you won't be going anywhere and if the tide is 3 knots or more (which it often is) you will end up going backwards! So I would get something a bit more powerful If I were you.
 
Only if it’s set up right and the cavitation plate on the kicker is below the line of the hull. Other wise it’s useless and cavitates sucking air from still water behind the transom. All about the height of bracket. Needs to be spot on to allow the above, but also so it doesn’t drag in the water at speed using main engine. Don’t even bother with the brackets that sit flush on the bathing platform. Waste of time. I’d also stick to a good 2 stroke auxiliary engine. Much lighter and more torque. Even the wee 2.5 4 stroke will see your boat list a little at rest. The wee 2.2 Suzuki 2 stroke is the best of them but command a high price for this reason. They weigh only about 10kgs.
 
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