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Upgrade your 40hp to 50hp

kentech

New member
"Hi !
I have a Yamaha 2-strok


"Hi !
I have a Yamaha 2-stroke 40hp with trim and tilt from 1992. The motor is in great condition. This motor did not go many summers with the previous owner. This due to a backproblem for him. The only thing he did every spring was to start the engine for lubing and cooling check.
Now onto my question : I have heard that the 40hp and the 50hp has the same block (693cc).
So if you change the carbs and the silencer you have upgraded your 40 hp to 50hp.This would be fun to test but I would like to know ,isn’t it something more to change or to tune ,like ignition or similar. Is it someone who has done this upgrade on this engine or similar ?
I know that the best way is to sell the 40hp and buy a 50hp-60hp and not dismantle a 15 year old engine. But if it is these parts I need to upgrade, the cost to get 10 more hp is very small instead of loosing a great deal to sell the 40hp and to buy a second hand 50hp or 60hp you don’t know anything about. Since I have heard this and do not know this, I thought I could ask in this forum .

Thanks in advance

Kentech"
 
"Kentech, Your 40hp is a detun

"Kentech, Your 40hp is a detuned 50, Yamaha did this with carbs that are a quarter inch smaller in dia. and an exhaust tube that's a half inch smaller. I upgraded my 40/28 jet and got 600 more rpms and a 5 mph increase in speed. I'd recommend buying a fried 50hp on ebay for the parts. If you do the project, you will have to disassemble the motor, lower unit and then powerhead, be really careful when prying on the powerhead it will be stuck to it's gasket at the top of the midsection. Take your time. It's a great motor, try to keep the WOT at 5500rpm. Mike"
 
Is this also true for a 2000 Y

Is this also true for a 2000 Yamaha 40 2 stroke outboard?
 
"Hello Michael !
Thank you fo


"Hello Michael !
Thank you for the answer.I will try to get the parts from a 50hp that has given up.I have to ask since i am a bit unsure what you mean. And this has to do with that i can´t technical english very good.(Sweden) I have to take the lower unit down that i understand ,and that is to change the silencer for a better flow out. And while that one is down should i change the water pump as well when its down ,is there a range when you should change the water pump ? Second question: the powerhead ,What do i have to remove except the carburators and its gaskets,Is it the complete powerhead or have i misunderstood ?
In that case is it to gain access to the silencer from above ?
And last qusetion : you wrote try to keep the WOT at 5500 rpm , what does it mean ? Im sorry for bothering you with these questions but i would be very thankful if you could take your time for my questions.

Best Regards

Kentech"
 
"Kentech, It's not too dif

"Kentech, It's not too difficult, takes me about 2 hrs to swap out the silencer. I'll gather up some diagrams with notes and send them to your email address. Michael"
 
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