Late 1980s 20hp yam wont rev out (flooding)

[lowdouble]

a 1986 (i think) Yamaha 20hp, that will not rev to over half throttle under load, I by accident knocked off the petrol pipe when sitting down and as the engine actually ran out of petrol, it peaked and put the 16ft sea nymph straight up onto the plane for 5 secs before cutting out.
I can recreate this by putting a kink in the fuel line manually, so shutting off the fuel, as the engine peaks I let in more fuel by straightening the line again and instantly kinking it again so affectively controlling and starveing the engine of fuel. It will tick over and troll just fine???

 

[99yam40]

Re: Late 1980s 20hp yam wont rev out (flooding)

Check fuel pump diaphragm for leaks and clean the carbs and fuel lines.
may have trash in the float needle and seat

 

[mutch]

Re: Late 1980s 20hp yam wont rev out (flooding)

do your fuel pump the diaphram will be leaking

 

[lowdouble]

Re: Late 1980s 20hp yam wont rev out (flooding)

Thankyou very much guys, I will try it today and get back to you.

 

[lowdouble]

Re: Late 1980s 20hp yam wont rev out (flooding)

Thankyou once again guys! the diaphragm is torn about 1" round the side. Will I need a defanite year of manufacture to get spare parts?
the engine serial no plate says.
Yamaha 20BM
s 005697
will this determine the age?

 

[99yam40]

Re: Late 1980s 20hp yam wont rev out (flooding)

Apparently that is a motor not sold here in the USA because I do not see a 20hp on any parts web pages

 

[lowdouble]

Re: Late 1980s 20hp yam wont rev out (flooding)

I dont seem to be able to find a 20hp either?
what does the serial no refer to, will that say where its made?

Can you post pictures on this forum and if so, would a picture of the fuel pump help (I guess they are all pretty generic).

 

[mutch]

Re: Late 1980s 20hp yam wont rev out (flooding)

yep

 

[lowdouble]

Re: Late 1980s 20hp yam wont rev out (flooding)

First of all I will start by saying it says Made in Japan on the engine plate!!!
so the origin question is answered. (embarressed face).
here are some pictures of the engine, and can I use another material to make my own diaphragm and if so what?