Yamaha 50GETO - power increase possible?

NeilH · 26 July 2009, 20:54

Hi, looking for a bit of technical advice.
I'm really pleased with this engine attached to my YAM480 - starts first time and doesn't miss a beat (unless I forget to undo the vent when I switch tanks!). Looking at the manual it looks like the 50, 60 and 70 HP engines are all the same capacity. So I was wondering whether it is possible to increase the power of mine in some way (other than buying an engine with more HP)?
Any advice would be appreciated.
Thanks
Neil

gibbo500 · 26 July 2009, 21:01

Quote:

Originally Posted by NeilH

Hi, looking for a bit of technical advice.
I'm really pleased with this engine attached to my YAM480 - starts first time and doesn't miss a beat (unless I forget to undo the vent when I switch tanks!). Looking at the manual it looks like the 50, 60 and 70 HP engines are all the same capacity. So I was wondering whether it is possible to increase the power of mine in some way (other than buying an engine with more HP)?
Any advice would be appreciated.
Thanks
Neil

Neil,

Although i cant offer you technical advice but there will be many that can shortly. I have the same engine and wondered what sort of speeds and RPM you are getting at the moment?

Cheers.

hatt11 · 26 July 2009, 21:21

Hi Neil,

I have a friend that had a 50 and had it altered to nearly 70. From what I believe it was changing the jets and fuel management. I may be wrong tho but is certainly possible, unless he was leading me up the path!!

NeilH · 27 July 2009, 08:41

Thanks
the fastest I've seen on the GPS is 29 knots although with a few people on it the max seems about 25 knots (haven't really had a completely flat day to try it flat out). I think max revs is about 5,000rpm.
Cheers
Neil

outboardtech · 27 July 2009, 10:23

NeilH ok this is a big ???? everyone asks . I have been down this road alot with my customers and spoken to various top engineers in America about this topic . If we could change jets etc in the carbs and mess around with the fuel systems then Yamaha , Merc , Mariner , wouldnt sell engines as everyone would just do thIS SAVING THEM ALL BIG MONEY . . I have tried changing jets and even though all the carbS etc look the same on the 40 , 50 , 60 etc the fuel and air passages are all different sizes within the units . Changing high , intermediate , idle jets would obviously make engines run either to RICH or LEAN causing piston detination , preignition etc . On the Mariner models there are a few small upgrades that you can make on the 25 and 30 models but as far as I know Yami and very different . Your best bet to get more performance is to play around with engine height , trim angle , and the most important of all PROPS . I wouldnt even consider trying to change parts around personally as you could run into running problems and cause serious powerhead damage . My opinion , cheers baz

NeilH · 27 July 2009, 18:24

Thanks Baz
very helpful - I did wonder if it might be complicated (I noticed that the compression ratio is different between the engines which did make me think). Now a new prop - something else to buy..........
thanks again
Neil

spartacus · 28 July 2009, 22:10

Quote:

Originally Posted by NeilH

Thanks Baz
very helpful - I did wonder if it might be complicated (I noticed that the compression ratio is different between the engines which did make me think). Now a new prop - something else to buy..........
thanks again
Neil

The Yamaha 40hp and 50hp share the same block. I considered a power upgrade some time ago, as it would mean changing the carbs and exhaust manifold from a 50hp. However, it could cause more problems than its worth and render a perfectly usable engine into a problematic one, certainly of you don't know what you're doing. I suppose the only real feasible alternative is to stump up the cash and upgrade in HP.

hobnob · 30 July 2009, 09:13

Quote:

Originally Posted by spartacus

The Yamaha 40hp and 50hp share the same block. I considered a power upgrade some time ago, as it would mean changing the carbs and exhaust manifold from a 50hp. However, it could cause more problems than its worth and render a perfectly usable engine into a problematic one, certainly of you don't know what you're doing. I suppose the only real feasible alternative is to stump up the cash and upgrade in HP.

The parts manual for my 8hp Yam shows that all parts in the 6hp version are identical except for the carb and the exhaust manifold. I would guess these are prohibitively expensive from Yamaha.

spartacus · 31 July 2009, 18:33

Quote:

Originally Posted by hobnob

The parts manual for my 8hp Yam shows that all parts in the 6hp version are identical except for the carb and the exhaust manifold. I would guess these are prohibitively expensive from Yamaha.

Could have kicked myself - but a set of carbs for a three-cylinder 40/50hp were on Ebay a couple of years ago. Sold for under £40! Have seen them advertised anywhere from £100-£300. Have never seen an exhaust manifold for sale. No idea what Yamaha would charge.