Tohatsu help

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Tohatsu help

Postby rabbitdundied » Sun Feb 02, 2014 8:36 am

hat options I have to modify my M40D Tohatsu. It is used for duck hunting and fishing mainly. On the rare occasion I have to boat race to a duck hole therefore this is the need to be faster. It is mounted to a CMC 130 on a 16' semi V aluminum boat. I am currently running a 14p Vengeance Prop. The boat normally runs with a moderate load. 2 guys and say 120lbs of decoys, guns etc. I say this to say that putting a 16p prop that will get me 1 MPH on top end won't help because any advantage will be lost trying to get out of the hole.

What I would like to know is what options do I have to upgrade the motor? Carbs, reeds, exhaust tuners or anything I may not be considering?


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Re: Tohatsu help

Postby T Man » Sun Feb 02, 2014 12:45 pm

rabbitdundied wrote:hat options I have to modify my M40D Tohatsu. It is used for duck hunting and fishing mainly. On the rare occasion I have to boat race to a duck hole therefore this is the need to be faster. It is mounted to a CMC 130 on a 16' semi V aluminum boat. I am currently running a 14p Vengeance Prop. The boat normally runs with a moderate load. 2 guys and say 120lbs of decoys, guns etc. I say this to say that putting a 16p prop that will get me 1 MPH on top end won't help because any advantage will be lost trying to get out of the hole.

What I would like to know is what options do I have to upgrade the motor? Carbs, reeds, exhaust tuners or anything I may not be considering?


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Motor Mods are useless without proper motor/prop setup. Get it propped right. A 14 p on a 40hp seems pretty steep
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Tohatsu help

Postby rabbitdundied » Sun Feb 02, 2014 3:45 pm

Thanks,

Is there anyone else? I would prefer someone with more experience than me.

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Re: Tohatsu help

Postby T Man » Mon Feb 03, 2014 3:27 am

You have already asked, and received an answer at tinboats.net, so what else are you looking for?
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Tohatsu help

Postby rabbitdundied » Mon Feb 03, 2014 5:59 am

Other ideas, resources where to find things etc. I am also asking this on boatracingfacts.com does this bother you?


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Re: Tohatsu help

Postby handyandy » Mon Feb 03, 2014 7:59 am

a 14 pitch prop is probably about as steep as you can go I have a nissan 40hp ns40d2 which I think is the identical nissan version to your engine and I have a 13p powertech prop and I wouldn't wanna go any steeper as it has a good top end and not a bad hole shot. I run mine on a 1554 excel so my boat is probably heavier than yours. I really don't know that there are to many mods you can do these engines to get much more power out of them. I don't think there are any performance reeds for them or anything at least I haven't found any but I haven't looked to hard. I don't know that nissan/tohatsu had a 50hp varient of these engines that had larger carbs or anything but I don't know that for sure. The only thing that I could think would help would be to have a jack plate to set the engine back so you could run the engine a little higher thus having less drag and a little more speed and you can run shallower. I plan on putting one on my boat at some point I figure even if it only lets me run my engine and 1-2" higher that is that much shallower I can run which sometimes can make a difference between running through a spot or push polling through. Plus having your engine one more inch higher is quiet a bit more of the lower unit out of the water causing that much less drag which is what will give you a little more top end speed.
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Re: Tohatsu help

Postby gearhead80 » Mon Feb 03, 2014 8:07 am

If the places you are hunting don't have an engine limit, you may want to just look into getting a different rig with a bigger engine and set up better. Modding a 40hp boat engine really isn't cost effective. There's not a lot of info out there on it because it doesn't happen much. I'm not saying never, but it's not like there's a bunch of hop up parts for them..

But if the new rig is not an option, prop testing would be the best place to start. You could be amazed at the gains from different props. Start with a smaller pitch to get more rpm on the top end and go from there.
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Re: Tohatsu help

Postby rabbitdundied » Mon Feb 03, 2014 8:30 am

Thanks for the replies. The motor is actually a m25d which is the Mega 25 which allows me to hunt in 25hp restricted WMA. That block is the same as the M40D and M50D. I have been prop testing already. So far a 14 p Twister is the best all around. It gives a great hole shot and still runs 41 with me at 250lbs. I have tried several props including 15p and 13p. The 14 is right for this motor. There are quite a few mods that can be done to these motors according to other sites. I have been asking on several sites to see if there is more information available out there. This site may not be the best venue to ask these questions on. Thanks anyhow.


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Re: Tohatsu help

Postby gearhead80 » Mon Feb 03, 2014 9:04 am

This post is now a little confusing. So you have a 40 and a 25? And you want to mod the 25?

41 MPH from a stock 25 on a 16' boat??? :huh:

From a small amount of info I just looked at, it looks like you need the reeds and carbs from the 40 hp model to go on the 25 model. Then you would need to adjust teh timing accordingly.

Or is looks like some people just ran the 40 hood on the 25 since they were the same engine..
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Re: Tohatsu help

Postby Garand » Mon Feb 03, 2014 9:24 am

Have you looked over on the Refuge Forums? there is a LOT of talk about the Mega25s over there.

I assume you have a Tach on the motor and know what RPM's you're running at with your current 14p prop?


Have you been testing loaded? When I first got my boat (1756 Edge w/Tohatsu 40) I was chasing overall empty speed.. For what, I have no idea.. I have no plans to run 40+ mph in the dark, and I never hunt alone. Sure it would be fun to know my little aluminum boat was that fast, but when is it ever empty? I changed my focus and opted to just get the best performance I could with it Loaded full.
I tweaked my motor height, and watched the Tach.. turns out my 13p stock prop runs right in the sweet spot and pushes my boat along at 33mph with 4 hunters(not small guys, probably pushing 1000lbs right there) a 70lb dog plus all the other necessary gear, blind bags, guns, decoys etc.

just my 2c..
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Re: Tohatsu help

Postby handyandy » Mon Feb 03, 2014 10:31 am

I think the op is saying he has a tohatsu mega 25 which is 40hp basically with a 25 hood I think they had smaller carbs and reeds than the 40 maybe idk for sure they may have been the same. Sounds like your already getting pretty good speed out of it 41mph as it's been stated already I don't think there is much you can do to get much more power out of it. Sounds like you have tested props and found what works best there. I'd say a jack plate would be the next best step to get a little more performance out of it. If there are mods that you have read about else where for the 40hp I'd like to here about it as I have a 40hp nissan. But I have never found any mods for it that would really get it much more power.
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Re: Tohatsu help

Postby T Man » Mon Feb 03, 2014 4:38 pm

Ask around on screamandfly.com. Those are they guys to go to for making an outboard fast.
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Re: Tohatsu help

Postby rabbitdundied » Mon Feb 03, 2014 4:39 pm

Thanks Tman I will.


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Re: Tohatsu help

Postby rabbitdundied » Mon Feb 03, 2014 4:44 pm

Garand that is close to what it will do loaded. Two guys and gear I am getting 36 consistently and 38 on occasion. I would assume with two more I would lose another 4 MPH. I am just playing around with my only toy. I want to be able to run the rivers in the summer and goof off with it and make it as fast as I can make it. I don't need anything else I just want to see what else I can do within reason. I am not going to weld the crank or lighten the flywheel or anything like that.


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Re: Tohatsu help

Postby rabbitdundied » Mon Feb 03, 2014 4:46 pm

Handyandy is right in what motor I have. I posted M40D because that is basically what a Mega 25 is with 25 carbs on it.


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Re: Tohatsu help

Postby lattehead » Tue Feb 04, 2014 10:41 am

1
Last edited by lattehead on Mon Jul 28, 2014 5:22 pm, edited 1 time in total.
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Re: Tohatsu help

Postby T Man » Tue Feb 04, 2014 11:42 am

rabbitdundied wrote:Handyandy is right in what motor I have. I posted M40D because that is basically what a Mega 25 is with 25 carbs on it.


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Do you still have the 25hp carbs on it? If not why not upgrade to the 40hp carbs and keep it under the 25hp cowl.
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Re: Tohatsu help

Postby rabbitdundied » Tue Feb 04, 2014 6:49 pm

Probably going to go with 50 HP Tohatsu carbs or even 70 HP Yamaha if I can find either.


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Re: Tohatsu help

Postby chillout » Thu Feb 20, 2014 11:15 pm

I have a set of brand new 70hp Tohatsu carbs that you would need. PM me if you are interested. I am assuming that you are in AR?
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Re: Tohatsu help

Postby Yuchi1 » Fri Feb 21, 2014 8:16 am

rabbitdundied wrote:hat options I have to modify my M40D Tohatsu. It is used for duck hunting and fishing mainly. On the rare occasion I have to boat race to a duck hole therefore this is the need to be faster. It is mounted to a CMC 130 on a 16' semi V aluminum boat. I am currently running a 14p Vengeance Prop. The boat normally runs with a moderate load. 2 guys and say 120lbs of decoys, guns etc. I say this to say that putting a 16p prop that will get me 1 MPH on top end won't help because any advantage will be lost trying to get out of the hole.

What I would like to know is what options do I have to upgrade the motor? Carbs, reeds, exhaust tuners or anything I may not be considering?


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Wouldn't it be less expensive to just get up and leave earlier than the other guy?
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Re: Tohatsu help

Postby chillout » Fri Feb 21, 2014 12:38 pm

^^^^ Because we can't leave the ramp before 4 am.
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Re: Tohatsu help

Postby Yuchi1 » Sat Feb 22, 2014 12:42 am

chillout wrote:^^^^ Because we can't leave the ramp before 4 am.


So, you're having a Formula 1 style race to the spot?

What a sucky situation.

Have you considered golf? :wink:
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Re: Tohatsu help

Postby chillout » Sat Feb 22, 2014 12:26 pm

Yuchi1 wrote:
What a sucky situation.




If your running a Mega with 70hp carbs, it's not too bad :thumbsup:
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Re: Tohatsu help

Postby Yuchi1 » Sat Feb 22, 2014 10:36 pm

Are you hunting Bayou Meto?
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Re: Tohatsu help

Postby rabbitdundied » Mon Mar 03, 2014 10:38 pm

On the very rare occasion.


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