Mariner 8 vs 9.9 HP four stroke outboard

danilo · 21 April 2008, 20:49

I have Mercury Mariner 8HP four stroke outboard.
Does anyone know the difference (apart from HP) between 8HP and 9.9HP Mercury Mariner four stroke models from 2005 & 2006 (2007)?
Both engines look the same and the data in the brochures is identical including the weight.
Have Mercury restricted 8HP in some way or 9.9HP has different carb&jets too? Would appreciate if anyone has any info on this.
Please see the photo of my 8HP below if this helps.

Locozodiac · 21 April 2008, 21:19

Quote:

Originally Posted by danilo

I have Mercury Mariner 8HP four stroke outboard.
Does anyone know the difference (apart from HP) between 8HP and 9.9HP Mercury Mariner four stroke models from 2005 & 2006 (2007)?
Both engines look the same and the data in the brochures is identical including the weight.
Have Mercury restricted 8HP in some way or 9.9HP has different carb&jets too? Would appreciate if anyone has any info on this.
Please see the photo of my 8HP below if this helps.

8 & 9.8 models are the same engine, both 209 CC, 8 carb restricted, that I know there isn't any 9.9 model in four strokes only in two strokes, next four strokes models/range are 15 & 20, both 351 CC, 15 being carb restricted. 8 & 9.8 weights the same 37 kilos, All Tohatsu made in Japan.

Happy Boating

danilo · 21 April 2008, 21:37

Quote:

Originally Posted by Locozodiac

that I know there isn't any 9.9 model in four strokes only in two strokes

Mercury/Mariner have been making 9.9 four strokes in 2004,2005,2006,2007 and 2008 see attached.Short shaft 8 and 9.9HP weights 38kg.

Locozodiac · 21 April 2008, 21:48

Quote:

Originally Posted by danilo

Mercury/Mariner have been making 9.9 four strokes in 2004,2005,2006,2007 and 2008 see attached.

Probably a special number series for Mariner/Mercury brand, Tohatsu has not a 9.9, anyway same CC for 8 & 9.9. Strange cause 9.9 and 15 used to be the same, only carb rstricted.

m chappelow · 22 April 2008, 20:39

i have a tohatsu 8 hp 4 stroke 2 years old and looking in the spec in the manual it is pared with a 9.8 the only difference that i can see is the main jet size and a different prop , everyone tells me that my tohatsu is just the same as a mercury /yamaha 8 hp 4 stroke.

ian parkes · 22 April 2008, 22:27

Could it be as i was told here that one manufacturer measures the power at the crank while the other measures at the prop ?? just an idea

danilo · 22 April 2008, 23:29

Quote:

Originally Posted by m chappelow

i have a tohatsu 8 hp 4 stroke 2 years old and looking in the spec in the manual it is pared with a 9.8 the only difference that i can see is the main jet size and a different prop , everyone tells me that my tohatsu is just the same as a mercury /yamaha 8 hp 4 stroke.

Are you able to post some pics of your outboard here?

reinier · 23 April 2008, 10:11

Quote:

Originally Posted by ian parkes

Could it be as i was told here that one manufacturer measures the power at the crank while the other measures at the prop ?? just an idea

No, since around '80-'85 all manufactorers switched measurement from crank to prop, 100hp equals roughly 85hp on the prop, so a 15% loss. Nowadays every hp measurement is @ the prop.

mdziam_78 · 06 January 2012, 09:18

Hi Everyone,
im looking for information about upgradeing the 8HP to 9.9.
In parts catalogue the differences are in Carburetor, main jet, main nozzle and plug serial numbers.
The ingnition components are the same.
Can someone tell me is there a chance to upgrade the motor without changeing the carburetor? - getting new main jet, main nozzle and plug?!
thanks
MDD

Turbodiesel · 06 January 2012, 19:40

Looks like the only difference is the carb.

mdziam_78 · 06 January 2012, 19:57

Any chance that carbs differs only at fuel jet? Or some others diameters are different?

lightning · 10 January 2012, 20:02

I'm not sure what to do here.
My existing 6hp engine performs pretty well on the boat, and it will do about 15mph with two adults on board.
It is a bit noisy when planing, but I guess any outboard motor will be noisy when you are sat about 20 inches away from it....
I guess I have to decide if the extra few MPH will be worth the £1,000 or so it will cost me plus my existing engine.
Probably not is my thinking at the moment. Better to wait a bit and then buy a bigger boat for open water use, keeping the SIB for the canal and Norfolk Broads.

lightning · 11 January 2012, 16:27

Sorry for any confusion. The post above should have been in another thread, the one about fitting a Tohatsu 9.8 to my SIB.
Can't delete it now...

quantch · 19 July 2016, 14:18

Hi, in the end, did you do the upgrade of your 8hp engine ?
I have same engine and would like to upgrade it as well.
Thanks

Jeza · 02 November 2017, 20:09

Yes i can confirm that the only way to upgrade to engine to 9.9 is with a carb swap. You can notice the difference between the two carbs. The 9.9 has a bigger carb throat.

I upgraded my engine beginning of this year and what a difference it has made.