Tohatsu MFS15C carb rebuild to 20HP

So I got a Tohatsu MFS15C and after studying the parts list, the only difference I can find between the 15 and 20 hp is swapping the following parts in the carb:

"main jet" to 3BJ-04421-0
"plug" to 3V2-03169-0
"slow jet" to 3BJ-04552-0
"main nozzle" to 3BJ-03141-0

However, there was an old thread that I found where Tohatsu Guru would check if the carb housing was identical as well but there was no answer to that question unfortunately.. From the parts list I can not see that there is any other difference than above?

Can someone help me out here, it seems to be a fairly simple way of getting the 20hp for just a few bucks I think. The other, more expensive, way of doing it is to swap the entire carb.

Re: Tohatsu MFS15C carb rebuild to 20HP

They are indeed different carb castings. Changing the jets and emulsion tube nozzle will make your 15 hp carb much too rich.

Re: Tohatsu MFS15C carb rebuild to 20HP

Thanks, I guess complete carb change is the only option then.

But isn't it strange that the parts list doesn't show different castings, I suppose that those are available as well.. somewhere?

Re: Tohatsu MFS15C carb rebuild to 20HP

By the way, how much is the needed carb (20hp one) in the US?

Here, the "3BJ-03100-0" carb is about $811..! (does anyone know someone who could sell me one?) :joyous:

Re: Tohatsu MFS15C carb rebuild to 20HP

Besides main jets, nozzles sizes 20 HP carb has wider fuel passages inside carb allowing more fuel in. The only thing you will gain swapping 15 for 20 carb parts is a bad performer engine + throwing money to the sewer.

Happy Boating

Re: Tohatsu MFS15C carb rebuild to 20HP

By the way, how much is the needed carb (20hp one) in the US?

Here, the "3BJ-03100-0" carb is about $811..! (does anyone know someone who could sell me one?)

3BJ031000M CARBURETOR, F20C (MF/EF)(Tiller) $243.92
3BJ031330M CARBURETOR, F20C (EP/EPT) (Remote) $243.92

Any dealer (including Elvin, or me for that matter) can provide you with one.

Re: Tohatsu MFS15C carb rebuild to 20HP

I had a look around the US sites but I could not find any who actually sold directly to Sweden, at least not by the looks of it at their term and conditions.

I'll have a look around again, and see what I find. I must also take into account the warranty detail regarding my engine when changing the carb I suppose..

Re: Tohatsu MFS15C carb rebuild to 20HP

Volvo Marine distributes Tohatsu in your area so they would be the one to contact.

Re: Tohatsu MFS15C carb rebuild to 20HP

I have checked the price in Sweden and its $811.. So another, cheaper, alternative would be preferred. Otherwise I end up with the same price I could buy a 20hp for in total.

Re: Tohatsu MFS15C carb rebuild to 20HP

If both 15 & 20 HP are same 350 CC, have same time advance, plugs, besides a carb swap will some other parts, adjustments be required ? If quoted parts are 1/3 price than of Sweden, personally would not think it over. Definitely EU prices are prohibitive.

Happy Boating

Re: Tohatsu MFS15C carb rebuild to 20HP

According to a thread I cant find now, the only difference is the carb. Well, except for the decals! I have found it in great Britain for $420 including shipping to me.. Still a bit higher than US price! But a lot cheaper than Sweden though

Re: Tohatsu MFS15C carb rebuild to 20HP

$ 176.00 GB/US price difference and 20 HP carb will make your boating day...

Happy Boating

Re: Tohatsu MFS15C carb rebuild to 20HP

Allrighty!

So what happened to the carb swap? A little follow up perhaps?

I got a new carb (from a very supportive person in US, thank you!) and installed it yesterday. The actual job was really easy to do as I expected.

And did I notice any difference, perfomance-wise?

Yes, the motor ran smoother with less vibrations, a bit silenter and of course had a bit more "oomphh". An interesting side effect was that my Hardline tach/hour meter started to work properly and was able to show proper idle AND max rpm at the same setting?! (see this thread: http://forums.iboats.com/honda-tohatsu-nissan-outboards/rpms-hardline-tach-hour-tohatsu-mfs15c-yes-another-rpm-prop-question-kind-607923.html (actally I got another one since they thought mine was defective, which I also thought.. so now I got two of them?

The boat also got the final push that made it a little more entertaining to run. Top speed, including family, increased from 16,6kts to 19,7 kts. I have not run it on flat water alone yet so I cant really tell you the max speed with only me in it, previously it was 20,6kts.

Overall, I am more than happy that I swapped the carb.. and so is my wife.

I really can recommend doing the swap from 15 to 20 carb if you are after the extra punch.