Converting Nissan 4hp to 6hp (4 Stroke)

NCSUDucker · Mar 9, 2010

I apologize if this has been asked. Tried searching it but "4" was too short for the search function.

It seems by looking at the overall specs and a few of the threads here, the difference in the 4/5/6 hp motor is the carb. Can someone comfirm? If this is the case, does anyone know the particular parts that need to be ordered? Lastly, if anyone has done it, how tough a job is it?

Thanks in advance.

Brad

lowkee · Mar 9, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

I'd be some shocked if a carb was the only change to make a 50% HP increase. Happy to be wrong, though.

pvanv · Mar 10, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

Yes, that is correct. The 4/5/6 difference is the carburetor. Yes, you do get 50% hp increase going from 4 to 6. Need your precise model and serial to get the correct part number. Available at any Tohatsu/Nissan dealer, including me.

DECK SWABBER 58 · Mar 10, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

Welcome aboard NSCUDucker.

I had the same problem. Try "four" stroke instead of "4" stroke.

You have come to the right place, their is a wealth of info here.
Happy hunting.

pvanv · Mar 11, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

The carb venturi/throat size is the difference between these motors. You cannot merely change jets, or the mixture will be wrong. So, yes... any Tohatsu/Nissan dealer can sell you the correct carb that will boost your NSF4 to an NSF6. They will need the model and serial to order the proper part.

NCSUDucker · Mar 11, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

Thanks everyone. I'll pull the model and serial number tomorrow.

pvanv, what's a ballpark price on the carb? Also if you don't mind answering another question, how hard of swap is it?

Thanks,
Brad

pvanv · Mar 12, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

Depending on whether you have the NSF4A, 4B, etc, (and serial number) the carb sells for about $106.70 from any dealer, including me.

There are 2 fairly long bolts with 10mm hex heads that attach the carb to the intake elbow. The bolts also have #2 phillips drive on their heads to start them. For the inboard bolt, you will want a short 10mm socket on a fairly long extension, or a very good screwdriver, because it's a bit close to the motor.

The bolts create a "sandwich" of the carb gaskets, insulator, carb, and intake silencer. Not too tricky, but better to do the change off the water, to keep from dropping bits overboard. It will take the usual amount of patience and skill to swap out the carb linkage rod and choke cable, fuel hose, etc., but all-in-all, a pretty straightforward job.

As always, after installing the new carb, you may need to reset the idle stop adjustment, and verify/adjust full throw of the throttle cable (from idle to WOT). You can get a parts list from Elvin's website at http://www.internetoutboards.com/PartsCatalogMenu.htm

JimXeod · Mar 18, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

Are there any adjustments besides idle and linkage to do on the new carb? There is no lean mixture or air/fuel adjustment correct?
Any info would be helpful.

TOHATSU GURU · Mar 18, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

No adjustment is possible on anything other than the idle set screw.

jathomas · Mar 21, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

can I buy the parts to convert the 9.9hp to 15hp 2 stroke, is it really a carb adj?
JT

sean whiteman · Mar 21, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

On the Suzuki DF9.9 (Four stroke) and the DF15 it is also just the carb.
And on the DF4,DF5,DF6.

TOHATSU GURU · Mar 22, 2010

Re: Converting Nissan 4hp to 6hp (4 Stroke)

No, there is no carb job. You merely replace the throttle/timing cam.

http://www.internetoutboards.com/product_list.asp?id=57

coish101 · Apr 7, 2011

Re: Converting Nissan 4hp to 6hp (4 Stroke)

I am looking at getting a 6hp Carb for my 4 hp mercury (2008) can you send me a price list, and some contact info so I can purchase 1.

pvanv · Apr 7, 2011

Re: Converting Nissan 4hp to 6hp (4 Stroke)

coish101 said:
I am looking at getting a 6hp Carb for my 4 hp mercury (2008) can you send me a price list, and some contact info so I can purchase 1.

Drop an email to paul@obersheimersails.com or call 716-877-8221 tomorrow (I'm out of the office today) and you can order the Tohatsu one for $110 plus freight.

avid_fisherman · Aug 9, 2011

Re: Converting tohatsu from 6hp to 9.9 hp

Re: Converting tohatsu from 6hp to 9.9 hp

Can I convert my 08 tohatsu 6 hp to 8 or 9.9? Your response is greatly appreciated. Thanks.

pvanv · Aug 10, 2011

Re: Converting tohatsu from 6hp to 9.9 hp

Re: Converting tohatsu from 6hp to 9.9 hp

First, you should be creating a new thread, as this one is over a year old.

The MFS6 is the largest 1-cylinder 4-stroke in the US market, so no, you cannot upgrade it.

Please DO NOT reply to old threads or hijack existing threads. Old threads of a technical nature are like a library book, Do Not write in them.

1. Old threads should be considered archives and used for reference only. Do not reply to them.

2. Do not take over someone else?s thread (aka hijack) with your own question, even if it is similar. If you have a question that has not been covered to your satisfaction in the archives, it is always best to start a new thread of your own.

3. If you have a question for the original poster (OP) and the thread is over 30 days old, send the OP a PM, he may not even visit the forums any longer, or may not notice your question in the old thread.

4. By starting your own thread, you will receive the maximum number of views by forum helpers that may not even notice your question when it?s posted at the end of someone else?s thread. And those answers will be specific to your particular issue.

simplystressed · Aug 10, 2011

Re: Converting Nissan 4hp to 6hp (4 Stroke)

Good info on this thread. Merc told me it wasn't possible to upgrade the 4/5/6 but I figured it was just the carbs. This clarifies that (for the tohatsu made ones)

Sea Rider · Aug 10, 2011

Re: Converting Nissan 4hp to 6hp (4 Stroke)

Most outboards Companies don't like to give straight answers about max updating detuned models, usually go by the branches, have legal issues about running a updated model whith cowl HP sticker saying another thing and users having water accidents. If you don't plan to change HP cowl decals, let other boaters using your boat/engine set up know you have a converted HP engine, just in case they want to sue you..

Happy Boating

simplystressed · Aug 10, 2011

Re: Converting Nissan 4hp to 6hp (4 Stroke)

Now is it a matter of just updating the carb for all year models of 4/5/6 4 strokes?

Sea Rider · Aug 10, 2011

Re: Converting Nissan 4hp to 6hp (4 Stroke)

simplystressed said:
Now is it a matter of just updating the carb for all year models of 4/5/6 4 strokes?

All mentioned models are 123 CC, asume cam swap on all, check parts manual, 4 strokes are not my ride...

Happy Boating

Converting Nissan 4hp to 6hp (4 Stroke)

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