Outboard rec for vintage 12ft Duranautic- 8, 9.9, or 15HP

[puffout]

I have 1986 12ft Duranautic, Currently using a Nissan 5HP outboard, and its a bit underpowered. The boat is rated for 10HP (but that was back in the day with lighter 2 strokes)
I would like to plane with 2 adults, should I get a new 8HP, 9.8HP, or,,,,, 9.9 or 15hp outboard? The weight of the latter outboards are about the same,
The transom is in good condition, with a new board.
Would a 15HP be too heavy or too much power?
I attached a pic of the boat.

 

[Stand Up]

If the boat will accept a 15 HP, get that. However a 9.9 would do the job quite nicely. Read the capacity label and see if it tells you what the maximum size outboard is recommended.

 

[puffout]

It says 10 HP, but it seems as if most 10, and 15HPwithin the same manufacturer weigh the same

 

[FuzzyGrub]

Most 15hp’s are “tuned” 10hp motors. A larger carb, different exhaust, ICM etc. They will usually have the same/similar torque for getting on plane, but the 15 will be able to achieve higher rpm’s, ie top speed.

A 10hp is usually plenty for a 12’ boat and sounds like that is the max recommended. IMO: A 15 will not be hazardous, but you need to consider the insurance and liability if something goes wrong. I don’t recommend the 15 for that reason.

 

[airshot]

It is the thrust difference not the weight. When the Jeff says 10 up then that is the max thrust it can handle safely ! What your saying is....if they made a 109 up motor that weighs the same as a 10 hp, that would be OK ??
God forbid any type of accident you might be involved with ( even not your fault) being overpowered automatically puts you at fault for negligence !! Not worth the gamble in any way. A good 9.9 should give you all the power needed to get up on plane and still be safe. However, being a two stroke fan myself, I would opt for a nice 9.9 two stroke, lighter, faster, easier to service !!

 

[puffout]

How about the 9.8HP Tohatsu? Even lighter, will it have enough power to plane a 12ft?

 

[Stand Up]

How about the 9.8HP Tohatsu? Even lighter, will it have enough power to plane a 12ft?

Yes, it certainly will. And that is a good new motor to buy as well.

 

[FuzzyGrub]

Yes, it certainly will. And that is a good new motor to buy as well.

I like the specs of the Tohatsu 9.9HP. It has one hundred cc more displacement (over 50% more) than the 9.8HP and looks to be the same block as the 15HP. It will have more torque to get on plane than the 9.8HP.

If it is a lifting issue, and you are planning to be installing/removing the motor on a regular basis, then the 9.8 might make more sense, but it is only about 10lb difference.

Myself, would go with displacement, especilly if it is a "heavy" 12fter, or plan on "heavier" loads.

PS: Looks like there are currently two versions of 9.8hp. The 9.8C looks to be EFI and 9.8B is probably carbed.

 

[Sea Antsy]

I have 1986 12ft Duranautic, Currently using a Nissan 5HP outboard, and its a bit underpowered. The boat is rated for 10HP (but that was back in the day with lighter 2 strokes)
I would like to plane with 2 adults, should I get a new 8HP, 9.8HP, or,,,,, 9.9 or 15hp outboard? The weight of the latter outboards are about the same,
The transom is in good condition, with a new board.
Would a 15HP be too heavy or too much power?
I attached a pic of the boat.

Ahhhh .. I love my DN12.... it'a been loved for a decade more than your young '86... and some observations... with any single cyl (like your 5hp and my 6hp Merc 4stroke) it is difficult to.. idle low enough to troll SLooow.. and the vibration from the single cyll shakes the minnows outta the bucket... and the whole tinny acts like a sounding board..
I got several hundred hours on my rig and am keeping my eye out for a 8hp 2stroke which will be about the same weight..
and I thought .. but may be wrong the TOHATSU (aka Merc) 9.8 was carbed and the 9.9 was EFI.. ..both are 4 strokes..

 

[Pappy]

In 1986, when your boat was manufactured, all of the recommended engines were lighter 2-strokes as there were practically zero 4-strokes out there. I have run quite a few 12' boats with 15. 18, 25, and 35hp engines on them and they were all a handful at WOT throttle settings if running a single person and light load. However.....there is that thing called a throttle on each one that you and common sense control. I would save a ton of money and get a late model 9.9hp 2-stroke and call it a day. Light and powerful. Most of those engines can be converted to 15hp without much of an issue once you go to a larger boat.
Example - 1974-1991 Ev/Jo 9.9-15hp manual weighed around 86#.
The 1992 and later was a few more # but was quieter and more friendly to work on. Have fun with your decision !

 

[Crazyboat]

A 10 will do you fine, the 15 won't hurt you.

 

[mbullen]

For what it's worth, HP Capacity and Weight Capacity are two different calculations.

HP capacity is based on boat dimensions and construction.
I have 14ft boats that are rated everywhere between 12hp and 40hp.

Weight capacity is based on displacement. It includes your motor, fuel, gear, and people.
Balance is up to you.
If you choose a heavier motor, and since you can't move it's position, you will need to adjust the other variables and their positions in the boat.

 

[KonradS]

I was in the same dilemma last year looking for a motor for my old Lowe Line scout. The scout is a very light, narrow, low 14' flat bottom, also rated for 10hp. I got a steal on an old '63 Gale 15hp & jumped on it. I rarely run it wide open as it gets pretty squirrelly and is a bit more of a thrill than I want, unless it is flat calm. When I am with a buddy and all the fishing gear and a full tank of gas, I am at or just over the weight limit for the boat- the motor weighs 77 pounds. the good news is that I can still scoot right along fully loaded. So, in the end happy with the setup, and I can cruise with the throttle backed off to a comfortable rpm