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Old 22 September 2012, 12:47   #1
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Country: UK - England
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Make: Avon Searider 4m
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Engine: 50hp tohatsu tldi
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25hp Tohatsu to 30hp

Tomorrow I am going to pick up a 4m honwave SIB with a 2006 25hp 2 stroke tohatsu on the back. Can these engines be modified to a 30hp on a reasonable budget? Sorry to be fussy but I would need specifics e.g. if there was a restrictor plate then where is it/what does it look like/maybe a picture sorry I am new to engines so if some just said a random part I would not know where it was.

Another thing was, what do you think of these engines? Are they reliable and would it push the SIB well? Would you be able to pull ringos and kneeboarders?

thanks, Henry. P.S. I am new
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Old 22 September 2012, 13:58   #2
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RIBase
i have a honwave t40 with tohatsu 20 4stroke goes well 5up .proper goes 2up would pull ringo no problem
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Old 22 September 2012, 17:28   #3
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thanks for the reply buddy
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Old 22 September 2012, 20:04   #4
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Boat name: Nautile
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Henry, you must change carb gasket, buy the 30 HP model and depending on the model advance +5 timing mark. A 30 HP will fly a 4 mt sib, just inflate well to factory recommended working pressure to perform as expected. There is plenty info on this section about modifying Tohatsu 25 to 30 HP , including pics of the procedure. A matter to search.

Happy Boating
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Old 23 September 2012, 15:17   #5
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If I were you I'd try the boat out with the engine on it first, you are worrying about the performance and have not even tried it out on the water yet!
Get the boat out on the water and see how it performs, you may find it goes like a rocket and you don't need that extra 5bhp.
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Old 24 September 2012, 13:01   #6
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The extra 5HP is at the end of the trottle, you can throttle less and behave like a 25 HP. If carrying more weight or total max allowed passengers, a must have. Both 25 and 30 models weights same, just 25 with restriction. For $ 7.50 go for it....

Happy Sibbing
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Old 20 November 2012, 08:30   #7
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25hp to 30hp 4stroke mercury.

Hello.
I am returning to boating after a long period away from the water. I am also new to forums.

Now that I have got that out of the way, I would like to know if it is possible to cost effectively modify a Mercury / Tohatsu 25hp 4 stroke motor to 30hp. In particular the EFI models.

I hope that someone can help.

Best regards.
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Old 20 November 2012, 09:10   #8
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Hi

Not worth it and you haev a great package so enjoy.

Dave
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Old 20 November 2012, 14:16   #9
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Hello Dave.
I was just having a wonder. Thank you for your extremely quick response.

On motor vehicles with EFI a small increase in bhp can be obtained, 10 to 15%, by de-restricting the air inlet tract because the Mass Air Flow Meter and Oxygen Sensor compensate for the increase in volumetric air flow whilst still staying within the original Engine Fuel Map. So, if the Inlet, of for that matter Exhaust, Tract had been restricted by using a reduced area gasket or by some other easily defeated means an easy 5hp could be gained.

You can even purchase a re-mapped chip for the Engine Management Module on motor vehicles. It looks like outboards have a little catching up to do.
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Old 20 November 2012, 17:27   #10
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Welcome to ribnet!

Thing with outboards is the market (compared to cars) is miniscule, hence not designing everything "bespoke". There are plenty ways to "de tune", as you say, a restrictor gasket, hard stops on the throttle mechanism, even different cams on the spark advance follower (Older machines the throttle advances the spark - the throttle is generally driven off that)

Newer machines, when you look at the relatively small market & cost differences, you can kind of see why they might want you to buy the bigger engine to get your extra gee gees! Have a trawl through the forums here - you will quickly find who resprayed what into their own livery, and what might be easily re-powered. Some it;s a siomple djustement, others you might as well buy the bigger engine by the time you have replaced the parts!

Thing with EFI is there is also a compooter to re-tune too.... What's yours hanging on? You may find 25 is plenty!

Pop back with Qs once you've had a search- plenty of opinion on here, average it out & you'll get a reasonable answer! (use "advanced" to keep it to the engine forums - Loco knows a fair bit about the Tohatsus )
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