Lately thinking to go from our old Mariner 9.9 to a _________ fill in the blank under 10hp four stroke. Just getting a bit old mixing gas etc. Engine hangs vertical in the davits.
Anyone that has changed from a two stroke to a four, noticed a power difference one way or the other ....Pros and cons..?
9.9hp.. 2 stroke vs 9.9hp.. 4 stroke
- bud37
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- Midnightsun
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Re: 9.9hp.. 2 stroke vs 9.9hp.. 4 stroke
Power wise they are the same more or less however the 4 stroke has a serious weight disadvantage. 57 lbs vs 94 lbs.
If weight is not a concern then 4 stroke all the way.
The old 2 stroke trick was to put 9.9 sticker on a 15 since they were exactly the same motors with slight carb and compression mods.
If weight is not a concern then 4 stroke all the way.The old 2 stroke trick was to put 9.9 sticker on a 15 since they were exactly the same motors with slight carb and compression mods.

- bud37
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Re: 9.9hp.. 2 stroke vs 9.9hp.. 4 stroke
Called a georgian bay 9.9 around these parts........actually I was going to add to the original post, the weight does matter...... 

FWIW.....The above is just my opinion.
- km1125
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Re: 9.9hp.. 2 stroke vs 9.9hp.. 4 stroke
Midnightsun wrote:Qr Bbpost Power wise they are the same more or less however the 4 stroke has a serious weight disadvantage. 57 lbs vs 94 lbs.If weight is not a concern then 4 stroke all the way.
The old 2 stroke trick was to put 9.9 sticker on a 15 since they were exactly the same motors with slight carb and compression mods.
That works with many of the four stokes too.
Definitely agree on the weight issue. If you or your boat can tolerate the extra weight, then go 4S. What are you putting it on? Will you have to take it off and put it back on while in the water?
Some of the inflatables will not have enough flotation in the tubes behind the transom, which can be a problem if you hang a 100+lb engine back there. Other inflatables will have the tubes extends behind the transom which provides plenty of support.
- bud37
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Re: 9.9hp.. 2 stroke vs 9.9hp.. 4 stroke
So until the other day I had no reason to check out small engines and I thought you could still buy a two stroke...HA....seems my little 9.9 is worth its weight in gold...Trouble is the change from 68lbs to around 100 is a real big hill to climb for us. Even the tohatsu from 15-20hp is around 95lbs.
This rib will take 20hp so if I change it will be to 15 and we have decided to get a trailer and keep the motor on the boat all the time. ....Engines , trailers when will it stop..
We may just keep the 9.9 and go slow in a cloud of smoke...( bug repellant )...
This rib will take 20hp so if I change it will be to 15 and we have decided to get a trailer and keep the motor on the boat all the time. ....Engines , trailers when will it stop..
We may just keep the 9.9 and go slow in a cloud of smoke...( bug repellant )...

FWIW.....The above is just my opinion.
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Re: 9.9hp.. 2 stroke vs 9.9hp.. 4 stroke
That 2 stroke is worth quite a bit nowadays as they are no longer produced. My dad has a 15hp yamaha 2 stroke of the last generation, not bad on smoke as the mix is 100:1. Just repaired it for him as the carb was gummed up. Bought a whole new carb on Amazon for $100, bolted it on and now it runs like a top. 

- RGrew176
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Re: 9.9hp.. 2 stroke vs 9.9hp.. 4 stroke
I still have my 97 15 HP Merc outboard. See no reason to get rid of it.
Rick Grew
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2025 Godfrey Xperience 2286 SFLX
2004 Past Commodore
West River Yacht & Cruising Club
