Convert 2008 4st 4hp F4a to 6hp?

[djdyna123]

Hi. Has anyone upgraded a 4st 4hp engine to a 6hp. Mine is a 2008 f4a model and everything is the same (2001 - 2008 4, 5, & 6hp) except the carb and potentially the exhaust port size. It's my spare engine but may aswell make it a little more pokey since it's capable. So basically swap out for the correct carb of the 6hp version and voila. ♂️

Or is the f4a a whole different block and only the F4B can use the 6hp carb?

[boscoe99]

What you do is open both parts catalogs. One for the F4LMHA and one for the F6LMHA. Have them side by side.

Then start comparing part numbers. Find the components that have different part numbers.

Remove the F4LMHA part numbered part. Install the F6LMHA part numbered part.

Just perusing the parts book and I see a different carburetor and a different CDI/coil assembly.

[ausnoelm]

This comes up all the time, look at the parts list for both models and note any differences, just putting on a bigger carb will not increase HP by 50%, it might use more fuel and foul plugs though.

[ausnoelm]

Posted the same time as me......

[boscoe99]

In search of the free horse power. Never ends.

[djdyna123]

I've already checked and as said above the only difference is the carb and cdi. Both can be gotten cheap. It's my spare backup engine so may aswell have it run the power it's capable of doing since they're all the same blocks and internals. Why not modify an old outboard when it's simply a watered down version.

Strange why someone told me only the F4B can be upgraded.

Was just wondering if anyone else successfully did the conversion, and any issues or straight performance increase.

[ausnoelm]

Usually the exhaust is different, just putting in more fuel needs the extra gas to "get out" or you gain nothing, that said, often the parts list will only list one part number, because the higher HP one is backward compatible with the lower HP but not vice versa, so in reality, it's all very hit and miss unless you know them inside out.

[boscoe99]

Let's make sure that we are all on the same page.

The first F4LMHA and first F6LMHA models offered here in the USA were dated 0909. September 2009. There was no 2008 model year F4A models. Yamaha stopped using model years in 2005.



The F4LMHA and the F6LMHA blocks have the same part number. Therefore, the exhaust ports are one and the same.

[boscoe99]

I've already checked and as said above the only difference is the carb and cdi. Both can be gotten cheap. It's my spare backup engine so may aswell have it run the power it's capable of doing since they're all the same blocks and internals. Why not modify an old outboard when it's simply a watered down version.

Strange why someone told me only the F4B can be upgraded.

Was just wondering if anyone else successfully did the conversion, and any issues or straight performance increase.

I read time and time again on the innerweb where folks say absolute shit. They have no idea what they are talking about. Typing on the innerweb to feel important I guess.

If one takes an F4A model and converts it to an F6A model, and the F6A model produces 50% more power than does the F4A model, then it stands to reason that the modifed F4A model will have 50% more power.

Instead of you relying upon some keyboard cowboy for advice, what don't you take the bull by the horns and do the modifications? Then come back here and tell us what you found out.

[boscoe99]

Try not to confuse an F6AMSH model with an F6SMHA model.

cute boys with brown hair

[djdyna123]

Excellent, the F6LMHA is also a single cylinder model isn't it?

So what part number is the carb and cdi of the F6LMHA?

Mine definitely says 2008 f4a (European model I guess?)

What's the difference between all the models, mines a short shaft (standard) roughly 17" transom mount to cavitation plate. I'm assuming the other versions are different shaft models and steering etc?

[Keithbaja]

OMG, go buy a 10hp and be done with it....

[boscoe99]

This is a US based website. You failed to tell us that you have a non US model.

Yes. The F6LMHA US model is a single cylinder motor.

What is the complete ID of your motor? Again. It will be useful is we are all on the same page.

[djdyna123]

Thanks for helping boscoe99. This number is all I have a pic of as I'm away

M140429909

[djdyna123]

I know the 6hp carbs have either the throttle on the side or top depending on year. And also there's a 6hp carb with a flat plate on the top. Where as on my f4a it's a bowl shape. I've seen a 6hp carb on ebay that is exactly the same as my 4hp, atleast from the exterior of it