Slow speed with dinghy..ideas on why?

Nick70

Active Member
Apr 20, 2016
206
New England
Boat Info
2006 Searay 260 DA 496 mag
RAYMARINE stuff.
Engines
496 Magnum
Bravo III
last year I bought a nice dinghy/ outboard set up.
A brand new, 8.5' aluminum hull, hypalon material dinghy weighing 70lb. With an also new 6hp Suzuki outboard. Short shaft as was appropriate for the dinghy.
So this past summer, I couldn't get the thing past 6kts. With two people.
With just me maybe 6.5. Weird and disappointing as I was hoping to be on plane and move effectively.
I've since brought the motor to a shop where it was thoroughly checked out and found to be in perfect running shape.
Anyone have any ideas weather or not this is just normal or perhaps I'm missing something?
Thanks.
I'm close to buying a 8hp 2stroke and selling the new Suzuki.
 

Here is my Zodiac 260 wood floor with a 6hp Tohatsu. With me in it it will get on plane and go pretty fast as in the video. With two people you need flat water and weight forward to get up on plane. You should do a bit better with the aluminum hull but I think your on the edge with a 6hp
 
what is the manufacturer recommended engine size for your boat? Some will give min and max ratings.
I think it was min 4hp, max 8hp. I got the 6hp due to weight limit of 55lb for the outboard, seeing as all the new ones are 4 stroke and 90+lbs
It's just so confusing why it's so slow.
 

Here is my Zodiac 260 wood floor with a 6hp Tohatsu. With me in it it will get on plane and go pretty fast as in the video. With two people you need flat water and weight forward to get up on plane. You should do a bit better with the aluminum hull but I think your on the edge with a 6hp
I am so JEALOUS! I have pretty much the same set up and a 6 knot max speed...
 
I'll bet it's not propped correctly. Go on amazon and buy a "tiny tach."

https://www.amazon.com/Tiny-Digital...UTF8&qid=1511963452&sr=8-1&keywords=tiny+tach

See if you are getting your WOT RPM. My guess is that you are not and need a less aggressive prop which will allow the engine to reach full rpm and hopefully get you on plane.

Just to be transparent, I have this one
https://www.amazon.com/dp/B00A43PKOE/ref=sspa_dk_detail_5?psc=1

It works, but is a pain because the wire is not directly attached to the unit, so another potential loss and I have to hang on to it while doing testing, wish I wouldn't have been cheap!

Josh
 
I had a 6hp 2 stroke (1969 Johnson 2 cyl with 2 blade prop) on our air floor 310 and was able to plane only with myself (180lbs) and had to shift around to get there. Top speed of around 12mph

Went to a 9.9 2 stroke merc this year and I'm scared to run it at WOT. I hit 22mph on a flat day in July but only for a second, it's very squirly at those speeds. I plane at 10-12 mph with two of us on board now though, very comfortable.
 
I had a 6hp tohatsu on our highfield RIB which weighed about 89lbs. It would only plane with me in it. I went to an 8hp tohatsu and i can get up on plane without a problem with me and 2 kids or myself and the admiral onboard but not all of us. Its much more fun these days.
 
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I'll bet it's not propped correctly. Go on amazon and buy a "tiny tach."

https://www.amazon.com/Tiny-Digital...UTF8&qid=1511963452&sr=8-1&keywords=tiny+tach

See if you are getting your WOT RPM. My guess is that you are not and need a less aggressive prop which will allow the engine to reach full rpm and hopefully get you on plane.

Just to be transparent, I have this one
https://www.amazon.com/dp/B00A43PKOE/ref=sspa_dk_detail_5?psc=1

It works, but is a pain because the wire is not directly attached to the unit, so another potential loss and I have to hang on to it while doing testing, wish I wouldn't have been cheap!

Josh
That thought occurred to me, but then I figured it should have the correct prop already, being as it's a brand new unit.
But I will definitely look in to it.
Thanks.
 
I also think you're just underpowered as has been stated. I used to have an 8.5' air floor with a 5 HP Mariner that would barely plane by myself. Forget about it with any more weight.

Now my 10.5' RIB with a 15 HP 2-stroke Merc will top out at 24 MPH with all four of us in it.
 
I’ve got a 10.5’ Newport (130 lbs) and a brand new 9.9 Merc 4 stroke and unless I put a lot of weight forward I have trouble getting it to plane. I bought a different prop for it but the season ended and I won’t get a chance to try it until next season. Honestly though, I’m not a fan of the 4 strokes for the dinghy. They weigh too much and lack the torque of the 2 strokes.
If I had it to do all over again I’d get a much lighter boat and a lighter 2 stroke motor.
I’m actually thinking of selling what I’ve got and starting over again.
 
I’ve got a 10.5’ Newport (130 lbs) and a brand new 9.9 Merc 4 stroke and unless I put a lot of weight forward I have trouble getting it to plane. I bought a different prop for it but the season ended and I won’t get a chance to try it until next season. Honestly though, I’m not a fan of the 4 strokes for the dinghy. They weigh too much and lack the torque of the 2 strokes.
If I had it to do all over again I’d get a much lighter boat and a lighter 2 stroke motor.
I’m actually thinking of selling what I’ve got and starting over again.

I have to agree. With our 290 being a small boat I find myself taking the motor on and off (davit system still under construction) and the ability to just lay it down or store it wherever is a huge advantage of the 2 stroke, not to mention the weight. I think our 1980 9.9 weighs like 65-70lbs or so.
 
I have to agree. With our 290 being a small boat I find myself taking the motor on and off (davit system still under construction) and the ability to just lay it down or store it wherever is a huge advantage of the 2 stroke, not to mention the weight. I think our 1980 9.9 weighs like 65-70lbs or so.
I think my 9.9 Mercury 4 stroke weighs about 90lbs. Way too heavy.
 
You want lots of power! Trust me. I currently have an AB 9'6" rib with a 25hp 2stroke. Does 30mph and is loads of fun.
 
Ballpark figure is probably 5hp per person if you want it to plane.
I had a 5hp years ago and it would barely plane a slat floor Zodiac.
 

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