Trying to get a feel for range on 9.9hp engine

[Croolis]

Hello.

I've got a Mercury 9.9hp 4 stroke (manual start) on order. It comes with a 12 litre tank.

Now obviously a proper "range" has far too many variables, so I guess the right approach is "how long will it run on 12 litres at full throttle"? Dunno.

It's 209cc. Doing totally unreliable arithmetic: My 125cc motorbike (which is fuel injected, mind - the outboard is carbs) will do ~260 miles in town on a 13 litre tank. Let's be ungenerous and say I'll do the same miles flat out (sort of) at a constant 60mph from full to empty. Simple division says call it 4 hours to do that. If I ungenerously halve that to account for the bigger cc on the outboard, I get 2 hours at full throttle endurance on the Mercury.

Would you experienced folks say you could get ~2 hours at full throttle(ish) on an 9.9hp outboard from a 12l tank? I am not expecting a "yes" .

I will be using the motor on a 3.2m air-floored SIB with inflatable keel, often will be two-up, looking at taking it inshore coastal.

Just trying to get a feel for tank upgrade required.

Thx for replies.

[chipko]

In my experience you’ll easily get at least three hours of spirited use out of a12l tank. Not 100% flat out for all the time, but that is rarely necessary. Just throttling back to 5000 ish revs once planing will improve mpg and hardly impact on speed.

Just stick to the thirds rule for fuel….A third to get there, a third to get back, and a third in reserve.

[Steve509926]

Very mixed speed, coastal hopping, 3.65 mtr sib, 2 up & dog & kit, 20hp efi - I just scrape 4 hrs.
Same rule as chipko mentioned, 2 hrs out, 2 hrs return and 5 - 6 litres (2 hours) spare in a fuel can.

[Croolis]

Oh that's good news, thx gents. Won't have to shell out for tank for a while then. Need to run in engine first anyway, and once I'm taking it to them coast, I'll be super conservative anyway cos newbie at that stuff. Cheers.

[willk]

3 hours - balls to the wall. Or all day fannying about

https://www.boat-fuel-economy.com/ne...port-en-LT.gif

[Fenlander]

Some real life data from when I owned a new Mariner 9.8 4-stroke (i.e. same engine under the hood) back in 2018.

Mixed use at sea mostly just off WOT (which was 15kts) after cruising out respectfully through the moorings with two adults in a 3.8 air floor... 4Nm/lit so using the rule of thirds as, like Chipko I do, you are good for about 32Nm on the 12l tank... or approx 2.5hrs running.

On the river speed limited to around 4.5kts, i.e. not much over a tickover, we were using less than half that figure at 9Nm/lit.

With a 3.2m flat air floor type you should do even better.

I'd say you'd be unlikely to need more than a spare 5l can. These are a better than average type that I use in 5l and 10l sizes.

https://www.bottomlinemarine.com/pro...SABEgJpj_D_BwE

[Croolis]

I'm going to make a loading trolley for this to put it in the back of my Mk2 Focus without hurting my back. Probably use wood. Wheels at the top of the trolley as well as the bottom so it goes into the boot on the top wheels. Maybe not even have wheels on the bottom, will use a sack truck for proper moving about.

There's Youtube vids showing these sort of builds but they all seem to have the motor held to the trolley by its clamps and not laid down on its side (like the instructions say for transport!). So it's more like when you have the motor in the upmost position when its mounted on the boat, if you see what I mean.

What do you lot think about moving an outboard in a vehicle (for hours) in this position?

Pic attached:

[Croolis]

Just noticed that there's threads talking about this sort of thing right now.

Chipko's trolley system looks very nice .

Everyone seems to still say laying it down. I'll have to wait until I get my hands on the engine (end of month), but I hope I can make a simple lifting trolley (more like planks with wheels on the top than a trolley) where I position the engine on it in a lay-down-on-its-side way, incorporating the awkward tiller control beneath it, and then seesaw into the boot.

I'm having a slow Friday afternoon at the office. Can you tell ?

[Steve509926]

Hi Croolis, this would fit your needs.
I think this is chipko's, I made one similar for my 20hp efi.
Picture is #10

https://www.rib.net/forum/f50/liftin...rds-90319.html

[Croolis]

Originally Posted by Steve509926

Hi Croolis, this would fit your needs.
I think this is chipko's, I made one similar for my 20hp efi.
Picture is #10

https://www.rib.net/forum/f50/liftin...rds-90319.html

That's the puppy, just like that (re-posts picture for reference). Thanks .

[User name]

Originally Posted by Croolis

I'm going to make a loading trolley for this to put it in the back of my Mk2 Focus without hurting my back. Probably use wood. Wheels at the top of the trolley as well as the bottom so it goes into the boot on the top wheels. Maybe not even have wheels on the bottom, will use a sack truck for proper moving about.

There's Youtube vids showing these sort of builds but they all seem to have the motor held to the trolley by its clamps and not laid down on its side (like the instructions say for transport!). So it's more like when you have the motor in the upmost position when its mounted on the boat, if you see what I mean.

What do you lot think about moving an outboard in a vehicle (for hours) in this position?

Pic attached:

Look up the specs on your outboard. They're pretty much all designed to allow storage in one orientation or another. Once you don't leave it down in the wrong orientation then you'll be fine (oil can backfill into the cylinder/manifolds/intake etc).

A cheapo car creeper might even be the job for what you describe.

[Croolis]

Originally Posted by User name

Look up the specs on your outboard. They're pretty much all designed to allow storage in one orientation or another. Once you don't leave it down in the wrong orientation then you'll be fine (oil can backfill into the cylinder/manifolds/intake etc).

A cheapo car creeper might even be the job for what you describe.

Yeah I know what it'll say (not taken delivery of it yet) - tiller side down. Curiously, the 2.5hp Mariner that I have right now is the opposite - tiller side up.

[User name]

Originally Posted by Croolis

Yeah I know what it'll say (not taken delivery of it yet) - tiller side down. Curiously, the 2.5hp Mariner that I have right now is the opposite - tiller side up.

I have the same Mariner (well, the 3.5 but it's essentially the same) and when transporting it correctly with the tiller up, oil leaked out of the little inspection window on the side. I didn't know until I took it back out of the car...

[Steve509926]

If it's a 4 stroke, no matter what HP it is or if its a Mariner or a Mercury, there will be two lugs on one side of the OB just below the cowl. That is the side which the OB should be lay down on.

[Croolis]

Originally Posted by User name

I have the same Mariner (well, the 3.5 but it's essentially the same) and when transporting it correctly with the tiller up, oil leaked out of the little inspection window on the side. I didn't know until I took it back out of the car...

Gutted . I never had that problem.

Yeah the two lugs on the 2.5hp are on the opposite side from the tiller.

[User name]

Originally Posted by Croolis

Gutted . I never had that problem.

I was just really unlucky, I'd imagine. The window hadn't been fitted perfectly, or maybe worked loose and allowed oil to seep out. Maybe worth inspecting periodically on these.