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Differences between 99 and 15 hp MSH two stroke

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drew_s

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"Hello, I am researching the p

"Hello, I am researching the parts differences between the two outboards. I thought the carb and the exhaust extension were the parts needed but after looking at the Yami website I think the carb part number is the same and could not find the number of the exhaust. The reed valves are only difference I could find. Can any one please help?

Thanks, Drew"
 
"Thanks reggie and J-I-T. The

"Thanks reggie and J-I-T. The reeds were the only difference I could find also. So you both don,t think the exhaust tube is a different number ? My next question is how much are reed valves? I want to get a bigger inflatable and a 15 hp. is recommended. Thanks again"
 
"I'm looking in my Yami ma

"I'm looking in my Yami manual and the jets do appear to be different as well as the reeds - just makes sence - a 15 has to breathe a little heavier than a 9.9

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I've done many 9.9 to 15 horse conversions (despite my advice to "leave it alone"). Own a pair of 9.9's and a 15 horse and done numerous "on water" (real life) tests of the differences between the two.

Ya, you are increasing the horsepower by 50% but that does not translate into anywhere near 50% more power on a motor this small (or on any motor for that matter).

Time after time the results are the same.

A 15 horse, on average, will give you 2-3 more mph at wide open throttle compared with a 9.9.

The 15 will burn more gas (about 30% more) if you run it wide open.

You don't see any difference until the last 1/2" of throttle. As they move up the power band a 9.9 or a 15 horse putting out 8 horses, still only moves you along at the power of 8 horses.

If you can do it cheap, and you lie to yourself, you can say how much of an improvement you notice.

If you can't do it cheap, then you "will" lie to yourself and say how much better "all that extra power is".

I could swap hoods between my 9.9's and my 15, take you out on the water and you wouldn't be able to tell the difference. It's almost purely a psycological thing.

Just don't jigger it up if you fiddle with it. At least if you do then you can justify buying a brand new 15 horse...."
 
"Wow, thanks for responses. I

"Wow, thanks for responses. I believe this is a 2006 model (682K S 1026073 K) 9.9 MSH build date 07/05.
When I got on the Yami Parts website it seemed like the later models had less differences than the older 9.9 two stroke to upgrade to 15 hp. I recently bought a used carb. on ebay (63V00 KF04) when I thought the carb. was a necessary change. Paid only 20 dollars. I belong to a small boat club which has alot of inflatables that have had the outboards tweeked. I wish only to keep it stock. I have read Graham Lambs many posts on this subject and dont want to trash this outboard. We just want a little more top end to keep up. I will pay a pro to make the changes. Is the nice parts breakdown that Graham posted for the model number that I have? Thanks"
 
"You can't compare a "

"You can't compare a "stock" build with a "franken outboard" that some guys put together.

With stock parts simply increasing the horsepower within the limitations of the powerhead rarely provides enough of an improvement to make even minimal work worthwhile.

Like I stated, I have done it for quite a few and disappointment and a thinner wallet are the main outcome of the process.

On most rigs, the majority of the available horsepower is needed just to get the boat up on plane, the next part of the powerband gets it up to a maximum hull speed (on a planing hull, a design actually has a max speed - there comes a point where the boat just won't go any faster no matter how many horses you hang on the back).

So in the case of going from say a 9.9 to 15 (on a rig rated for 15 max), the 9.9 gets it most of the way to it's max speed, an extra 5 horses just pushes it that 'little' bit faster.

If you fit a boat with a motor that is 80% of the max rating for the boat, it will perform exactly as designed and get you the best fuel economy (not really a huge factor on a small motor)."
 
"G.L. you are correct that I f

"G.L. you are correct that I feel no difference in 80 percent throttle and 100 percent. Our present inflatable has a inflatable keel with a wood bottom and I agree this hull design has limitations. Our new inflatable will have a hard(fiberglass) bottom and these will really move and most have 15 hp. No frankensteins here , I just wish I would have bought the 15 hp. two years ago. I rechecked the Yami website last night and the carbs and jets were the same for both engines with the reeds having a different part number. It may end up being too much cash for the results but I still would like to know. I may have just become a registered user but I have posted and lurked for some time. I bought the Yami two years ago on your recommendation and I love its performance.
Drew"
 
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