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Old 07-16-2012, 12:54 PM   #1
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Achilles LEX96 w Merc 15hp 2-stroke

I currently run a small Honda 4-stroke 2 hp motor on my Achilles LEX96 (9.5 ft, 15.5 inch tubes, non-RIB with inflatable keel). It's woefully underpowered, but it gets me from boat to nearby boat or shore. It's just not enough to cross busy waterways like the San Joaquin River in the delta or Raccoon Straight in the bay. It feels like crossing a freeway on a skateboard!

I have an opportunity to purchase a lightly used Merc 15hp 2 stroke that I'm considering for this dingy. It should scoot the dingy right along! It's a deal from my best friend that is hard to refuse. But there are a couple of issues:

1. The Honda weighs in at 27 lbs and is a piece of cake to manhandle. The dingy is rated for a 84-88 lb motor (depending on what you read) and this motor is 77 lbs. This weight is the same as the Merc 9.9 2-stroke and within 4 lbs of the Merc 8 2-stroke. At 77 lbs, the Merc will require more finesse to mount/demount. Does anyone on the forum handle a motor this size without a davit or crane/boom? I suspect I'd be towing the dink more than I currently tow due to the weight. I currently secure the dink along the swimstep on its stbd side secured to the step and aft rail.

2. The max HP rating on the dingy is 8hp. I'm curious if anyone here has any experience with a non-RIB dingy with this motor? Is it too squirrelly?

I will be trying it out on my dingy before committing to the purchase but am very interested in the experiences of those on the board who have already traveled this road.

Many thanks!
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Old 07-16-2012, 01:08 PM   #2
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This is way too much power than what you want (and can safely handle) on such a small craft, especially if the engine is a 2 stroke. I had a 8.5 dinghy (inflatable keel like yours) with a 2 stroke 9.8 Mercury at one point. I had to be very careful when accelerating because the nose would just lift in the air right away. Not so bad when I had passengers or cargo but when alone I had to be very, very gentle with the throttle otherwise I would have fliped the thing in a second. Sold the engine after one season and got a smaller one. 15 HP on a very light rubber boat, that is just asking for trouble in my mind. My two cents.
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Old 07-16-2012, 01:17 PM   #3
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Greetings,
Mr. Flywright. I used to have the very model you own. Initially 2HP Johnson. Bit the bullet and got an 8 HP Evinrude. Used to store the dink only on a frame over aft cabin deck with the use of the boom and manual labor. I never did but I came VERY close on several occasions giving the "8" and myself a complete wash trying to get it up to the aft deck where it was stored on a bracket (boom wasn't long enough to use it effectively for this purpose). Just consider, in your case, for a moment, trying to mount and de-mount that 77 or greater lbs. (in the case of the 15HP) with a bit of wave action and the dink essentially being on ball bearings.
Later went to davits, again manual, where I could haul the whole works into place. Worked a LOT better.
I think the major consideration will be that the rating for the dink is 8HP. Anything over that will probably void your insurance.
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Old 07-16-2012, 02:05 PM   #4
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I agree with RT and Fotoman; to much engine.

See if you can find a 5 hp 2 stoke. On two older inflatables we had a 5 hp Nissan (Tohatsu) 2-stroke. It would plane, when properly inflated with Lena and I. The engine weighed ~46 lbs.
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Old 07-16-2012, 03:46 PM   #5
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Maybe I should consider a new dink to go along with my new motor ...hmmmmmm... then I'll need a davit system.

I'll try to get some pics/videos of my test drive just for fun. But I'm confident you guys are right...too much motor.
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Old 07-16-2012, 03:50 PM   #6
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Greetings,
Hmmm...videos eh? Just don't have them posted posthumously.
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Old 07-16-2012, 03:56 PM   #7
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If you don't hear back from me, you know it all went terribly awry!
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Old 07-16-2012, 04:01 PM   #8
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Quote:
Originally Posted by FlyWright View Post

I'll try to get some pics/videos of my test drive just for fun. But I'm confident you guys are right...too much motor.
This ought to be really good! I mean really good!

Like, "hold my beer, and watch this".
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Old 07-16-2012, 04:19 PM   #9
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Yep! It's time for an Achilles 310 or similar ( 10', 4" I think). Mount on swim step with davits and one of "those swing-type motor mounts so the engine can swing vertical when the dink's on its side" (17 words to describe what I don't know!).

I have a "dolphin" thingy on my 15hp engine which helps to keep the bow down for those five-beer drag starts...

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Old 07-16-2012, 04:28 PM   #10
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That's what I'm thinking Moonie! I hope I'm at least able to provide y'all with an appropriate level of entertainment for your dollar.

Ray, my buddy is mounting a whale tail on the motor this week to tame the bow rise on his 11' Boston Whaler. He's shopping for a 25-30hp replacement and when he finds it, I can buy the 15. If I get to the boat this weekend, we might mount the Merc 15 to my dink for a fun run. Wish me luck!!
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Old 07-16-2012, 04:30 PM   #11
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You got it!
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Old 07-23-2012, 11:34 AM   #12
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I suspect that lots of applied power will be exciting to ride thru. I've got a 10'2" dink w/ a Honda 5 four stroke. I use Weaver snap davits on the swim platform in combination with a St Croix Jr crane. The Honda weighs about 50+ lbs. There have been days when I was reallly glad everything was attached to something, or else the engine & I would have been wet. Currently considering going to 8 or 9.8 hp. More for smoother running/less vibration than going faster (yeah, sure). Currrent, as well as planned, configuration of boat & motor adds 150 to 180 lbs to swim platform/transom structure, really not sure I want to add more than that.
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Old 07-23-2012, 01:48 PM   #13
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I didn't get out to the Delta this weekend, so the video will have to wait.

Here's a pix of how I currently carry the dink. If you look closely, you can see the OB on the stbd side. Since the Honda can be stored on its stbd side (handle up) or vertically, I leave it attached to the dink when I haul it onto the swimstep. No need to mate/demate the OB away from the slip.

It currently weighs just over 100 Lbs. I'm hoping with the addition of 50 lbs of motor, I can still do the same with the Merc.

Does anyone know if manual start Mercs can be DIY converted to electric start?
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Old 07-27-2012, 01:32 PM   #14
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Got out for a test with the Merc 15 mounted. At intermediate power settings, the dinghy was stable and predictable. At full throttle, the ride was much more thrilling. The directional stability degraded quickly as the boat wanted to pivot (yaw) left and right easily with minor steering inputs. Also, high speed turns were an exciting exercise. I suspect due to prop torque, the high speed port turns were less stable than the stbd turns.

Rapid starts were controllable with minimal bow rise due to the whale tail on the motor. Runs 1 and 2 were made with a tiller handle extension and me seated on the bench seat. No significant bow rise was experienced with this loading. When I removed the extender and sat aft on the stbd tube for Run 3, there was a brief bow rise in the hole shot until the whale tail became more effective and the bow immediately settled down.

Full power hole shots caused acceleration so rapid that I had to hold on to the bridle to stay in potition. In the end, no damage, no injuries and I had a little fun in the process.

Clearly this engine needs a larger dinghy. I have some small keels that can be added to inflatable kayaks or dinghies that I might play with to see if they improve the directional stability. But if I buy this motor, I'll be shopping for a more suitable dinghy.

Here are the videos. Click the images below to view the video.

Run 1



Run 2


Run 3
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Old 07-27-2012, 01:49 PM   #15
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Clearly this engine needs a larger dinghy.



Now that's what I call PERSPECTIVE!
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Old 07-27-2012, 01:50 PM   #16
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How in the heck were you able to hold on to your beer during those hole shots?
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Old 07-27-2012, 03:10 PM   #17
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It wasn't easy!
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Old 07-27-2012, 06:14 PM   #18
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Darn! You definitely are a Jet Jockey.
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