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Old 08 February 2023, 07:54   #1
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Tohatsu fuel ratio.

Morning all. I’ve just taken ownership of a 2005 tohatsu 9.8 2 stroke. I know tohatsu recommend a fuel/oil ratio of 50:1, I fired her up for the 1st time yesterday and it smoked like hell even after running for 5 mins, which Also produced some oil residue around the back of the prop. My last 2 stroke merc was 100:1. Can anyone shed some light on that exact same engine and what they run fuel/oil. It’s definately running too rich. Many thanks. Click image for larger version

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Old 08 February 2023, 11:12   #2
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Fenlander may see this post and reply, he’s an expert on this engine [emoji106]
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Old 08 February 2023, 12:12   #3
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That looks ace.

Can confirm they run 50:1
Tohatsu recommend you run in for the first 10 hours at 25:1. As good practice we also fire ours up initially at 25:1 on half a tank at the start of the season.

Ours is a tad smoky at tickover on 50.1 and even tolerates the 25:1 without fouling….mind you we don’t faff around much at trolling speeds.
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Old 08 February 2023, 15:20   #4
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Originally Posted by maverick58 View Post
I know tohatsu recommend a fuel/oil ratio of 50:1Attachment 142112
I had one of these - 50:1 is correct. Unless you are running at high revs all the time you will get residue. If you are a potterer, then I would suggest that you might consider 75:1. The previous keeper of my engine was a fisherman and he ran it on 100:1 - it didn't seem to cause any issues with it.
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Old 09 February 2023, 09:32   #5
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I’ve owned two of these and done the 10hrs running in at 25:1. Even at that oil heavy mixture I didn’t find the smoke terrible. I now use 50:1 and it’s fine. I always use Quicksilver oil, what’s your brand of choice?
Are you adding anything to the oil like a stabiliser! Are you 100% sure of your mix ratio?
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Old 09 February 2023, 17:18   #6
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Originally Posted by Fenlander View Post
I’ve owned two of these and done the 10hrs running in at 25:1. Even at that oil heavy mixture I didn’t find the smoke terrible. I now use 50:1 and it’s fine. I always use Quicksilver oil, what’s your brand of choice?
Are you adding anything to the oil like a stabiliser! Are you 100% sure of your mix ratio?

I’ve been using 2 stroke outboards for quite a few years so it’s deffo the right ratio. Fresh fuel and fresh quicksilver too. When some 2 strokes run at 100:1 I must admit a 100ml of oil does seem like a lot for just 5L’s of fuel. Pulled the plugs and they seem to be a bit wet indicating over lube & running rich. Previous owner was adamant he ran at 100:1 plus a bit on top for good measure.
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Old 01 March 2023, 18:41   #7
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Hi all. My first comment here. Questions! How do I actually create a post? I'm looking to buy a Tohatsu 9.8 2 stroke. I am in Greece, and of course can not buy new. I have found a seller in the Channel Islands but not sure if it's the way to go. I'd like to create a new post entirely and source information and insights. Thank you kindly, Hinton
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Old 01 March 2023, 19:16   #8
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Hi all. My first comment here. Questions! How do I actually create a post? I'm looking to buy a Tohatsu 9.8 2 stroke. I am in Greece, and of course can not buy new. I have found a seller in the Channel Islands but not sure if it's the way to go. I'd like to create a new post entirely and source information and insights. Thank you kindly, Hinton

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Tap the highlighted button and create post. Choose a section to post your Q to. Do they not have 2nd hand tohatsu’s in Greece?? The channel island supplier might be able to arrange international shipping from their end. Or perhaps find the tohatsu distributor for your country.
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Old 01 March 2023, 20:33   #9
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@maverick58 Hi. Thank you. Unfortunately they are not available in Greece or the EU due to emissions regulations. Also, there are none currently in the used market. I think, when they do show up, they are expensive and bought up quickly. I stupidly sold my old Johnson 9.9 last week, but now have decided to go with a bigger RIB, and so I need a strong, lightweight engine again. Seems a 2 stroke is the way to go. I'll be creating a post shortly! Thanks again, Hinton.
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