Tohatsu 4hp parts to make it a 6hp?

[RobsJonBoat]

A friend of mine has the Tohatsu 4 stroke 4hp<br />outboard. Since the 4,5,6hp are nearly the same<br />what parts would he need to turn his from 4 to<br />6hp?<br />Thanks.

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

Three carburetor parts:<br /><br />3R4032520M<br />3R4032510M<br />3R4032540M

 

[RobsJonBoat]

Re: Tohatsu 4hp parts to make it a 6hp?

Thanks very much! I assume they could be ordered<br />from your website?

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

The parts are available from any Nissan/Tohatsu/Mercury dealer.

 

[jmoser]

Re: Tohatsu 4hp parts to make it a 6hp?

Great info on the carb parts - many thanks!<br /><br />I am interested in this same issue. In addition to the carb parts, how do you handle the RPM issue? The 6 hp is rated 6000 RPM - doesn't the rev limiter ('over rev protection') on a 4 hp cut out before you reach rated speed for the 6hp?<br /><br />Alternate question - is it feasible to retrofit the 6 hp with an internal fuel tank as found on the 4 hp model?

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

There is no rev limiter on the 4, 5 or 6. Yes, you can retrofit the integral fuel tank onto the 6.

 

[Marion Moore]

Re: Tohatsu 4hp parts to make it a 6hp?

How much might the parts for the conversion cost? Also, will the same parts work on the Merc 4 HP? They are exactly the same right?

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

You would need to call your local dealer for the parts cost, but it's around $27.00. And yes, the Merc and Tohatsu are the same

 

[Marion Moore]

Re: Tohatsu 4hp parts to make it a 6hp?

Thank you. The gears are turning. Boy are they making $$$ on the difference in the 4, 5 and 6 HP.

 

[gcapreol]

Re: Tohatsu 4hp parts to make it a 6hp?

Elvin - You seem to be a master of this topic. One question for you if I may...are these part numbers the same for 2 stroke and 4 stroke? <br /><br />I have a Mercury 4hp 2 stroke, which has a Tohatsu engine, and would like to try an upgrade to 5hp. <br /><br />- Gordo

 

[tooeagle]

Re: Tohatsu 4hp parts to make it a 6hp?

Just wanted to know how this ended up. Were you able to find the parts to upgrade the 4 hp to 6 HP. I have a 4 HP mercury and would like to increase the power to 6 HP.<br /><br />How did it go? Also, is there a way to get the mixture plug out without destroying it?

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

I was in error earlier about the parts you need to upgrade the engine to the six. You have to buy the six carb. The three parts I listed earlier will not upgrade the engine unless you also do something with the fixed air speed jets in the carburetor. Those jets are not removable. You could drill them out...but, I have no idea what the spec would be.<br /><br />On the two-stroke 4 verus the two-stroke 5. There are two parts that are different. One jet and the air mixture screw. Since Tohatsu never imported the 4 into this country I am unsure as to whether the carb body is different. History would indicate no and the two parts would be all that you would need. But, The 4-stroke was a surprise when I found out about the fixed air speed jet. We never see the Mercury/Tohatsu 4 so I don't have a way to experiment on one...

 

[grahamboating]

Re: Tohatsu 4hp parts to make it a 6hp?

Similar question to the last ones but different engine size, I am thinking of buying a Tohatsu 8hp and would like to make it a 9.9. Can that be done straightforwardly and at a reasonable price?<br /><br />Thanks GDDC

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

No.

 

[grahamboating]

Re: Tohatsu 4hp parts to make it a 6hp?

worth a try, the engine size etc all seemed the same, the only difference in the spec's I could see was that the 9.9 runs at 500 rpm more than the 8.

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

Different block, although it has the same cubes.

 

[dennisivor]

Re: Tohatsu 4hp parts to make it a 6hp?

Did I get that right, I will have to buy a 6hp carb to upgrade my 5hp merc 4 stroke

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

Yes, that's all you have to do.

 

[edgarwu]

Re: Tohatsu 4hp parts to make it a 6hp?

Elvin,<br /><br />I have similar question to the others; I have a 198? Honda BF75 (it is a 7.5 HP). As I was reading the engine specs., it has exactly the same measurement as a BF100 (9.9 HP). I suspect that I could make some minor cab modification to turn my 7.5 HP into a 9.9HP. I am wondering if you have any information regarding that at all, such as parts that required or even a online shop that I can get the kit from, thanks for your help.

 

[TOHATSU GURU]

Re: Tohatsu 4hp parts to make it a 6hp?

I remember that you could change the mid 90's 9.9 into a 12 by removing the throttle stop screw, but I have no idea if you could bump the old 7.5 up. There might be a cam difference or carb difference. There might even be a block difference. I would contact a friendly Honda dealer and ask them to check the parts book for number differences. The older the dealer the better off you will be. There is a tendency among newer dealers to blow off any parts sales on the older stuff. I'm a little surprised you have one that still runs. They had a lot of cooling system degradation on that frame if it was used in saltwater.