25 c2 tohatsu id like to run a hotter plug

[kajunsquirrelly]

I have a 25 c2 tohatsu id like to run a hotter plug what are yall suggest it calls for br7hs 10. I'm running 34mph on a 1546 express flat bottom i shaved my head 15 thousandths tuned the carb there is no restrictor plate and timing is set at 25tdc plus i have opened up my exhaust id like to go faster and need some advice

 

[pvanv]

Re: Tohatsu NGK Spark Plugs

Re: Tohatsu NGK Spark Plugs

You have already converted to 30 hp.
What is your plug color now? If it is tan, do not go any hotter. Too hot on a 2-stroke=burned pistons.

 

[Sea Rider]

Re: Tohatsu NGK Spark Plugs

Re: Tohatsu NGK Spark Plugs

Kajunsquirrelly,

You need to go for the Tohatsu M40C, right next to the 30 HP. Or install an induction tach go full wot with you alone with just 2 gallons of fuel, with well engine transom height seated and well trimmed on a flat calm no windy sea and check your max rpm achieved, if less than 5850 rpm go for a less pitch prop to bump your rpm higher till matches max wot factory stated numbers. Don't hallucinate flying direct to Mars...

BTW, how did you recorded 34 MPH, on a accurate GPS ? seeing a posted pic of GPS data is believing.

Happy Boating

 

[kajunsquirrelly]

Re: Tohatsu NGK Spark Plugs

Re: Tohatsu NGK Spark Plugs

You have already converted to 30 hp.
What is your plug color now? If it is tan, do not go any hotter. Too hot on a 2-stroke=burned pistons.

its a dark brown is that ok

 

[kajunsquirrelly]

Re: Tohatsu NGK Spark Plugs

Re: Tohatsu NGK Spark Plugs

Ill get you the pic next time i go out

 

[aspeck]

Re: 25 c2 tohatsu id like to run a hotter plug

I moved your posts to a new thread all your own, kajunsquirrelly. This way it will get more people to look at it and respond and it won't hijack someone else's thread.

 

[kajunsquirrelly]

Re: 25 c2 tohatsu id like to run a hotter plug

I moved your posts to a new thread all your own, kajunsquirrelly. This way it will get more people to look at it and respond and it won't hijack someone else's thread.

ok thanks sorry

 

[Sea Rider]

Re: Tohatsu NGK Spark Plugs

Re: Tohatsu NGK Spark Plugs

Ill get you the pic next time i go out

Ok, but need to know you max wot rpm for going 34 MPH, could go + 34 or more MPH, but that's surely over revving as hell, that situation ain't healthy for the horse as you could experience kabum and kaput associated issues in the short run...

Happy Boating

 

[kajunsquirrelly]

Re: 25 c2 tohatsu id like to run a hotter plug

I stand corrected the motor is a c3 and wot range is from 5000-6000 rpm i still have the sticker on the side of the motor its a 2000 yr model

 

[kajunsquirrelly]

Re: Tohatsu NGK Spark Plugs

Re: Tohatsu NGK Spark Plugs

And the tohatsu 40 is impossible to find around here ive been looking for one for a while now

 

[Sea Rider]

Re: 25 c2 tohatsu id like to run a hotter plug

I stand corrected the motor is a c3 and wot range is from 5000-6000 rpm i still have the sticker on the side of the motor its a 2000 yr model

Some tech issues,

That 25 C3 must hace come factory timed to 25? + carb restrictor plate, 20? is for the 25 C2 model. Just a restrictor plate was needed. If you bump a 25C3 to a 30C3 the wot factory parameters for that engine are 4800-5500 rpm. Assume side letters for next higher upgrade must match same letter ending. So if running at 34 MPH on a converted engine with more rpm than specified for that conversion is consider over revving. What would like to point out is that if you like running wot all the time like a bat out of hell that engine will surely not last that long...

Let's hope the Apostles chimes in to clarify if once converted a 25C3 to a 30 HP will have a final 30A3 or 30A4, both are 430 CC but runs at completely different wot rpm parameters.

Happy Boating

 

[pvanv]

Re: 25 c2 tohatsu id like to run a hotter plug

Yes, without restrictor, you use the 30 hp specs. What RPM is the motor running (at WOT) now?

 

[kajunsquirrelly]

Re: 25 c2 tohatsu id like to run a hotter plug

I don't have an tach for it when we rebuilt we borrowed one and it was puttin out between 5400 - 5500 rpm

 

[pvanv]

Re: 25 c2 tohatsu id like to run a hotter plug

I don't have an tach for it when we rebuilt we borrowed one and it was puttin out between 5400 - 5500 rpm

Get a tach on it...

 

[Sea Rider]

Re: 25 c2 tohatsu id like to run a hotter plug

If bumping a 25 C3 to a 30 C3, you're top of wot rpm factory stated for that C3 model which is 5500 rpm. Have not been clarified yet if bumping a 25 C3 to a 30 HP will give you a 30 C3 or 30 A4 as both runs at different wot rpm factory stated....?

Happy Boating

 

[kajunsquirrelly]

Re: 25 c2 tohatsu id like to run a hotter plug

How can tell the difference between the 2

 

[pvanv]

Re: 25 c2 tohatsu id like to run a hotter plug

It becomes a 30A4. There isn't any 30C. Max WOT RPM spec is 5150-5850. 5400-5500 is OK, but I would personally prop for a little more; if you prop for 5800 WOT, you will get better hole-shot than if propped for 5400 WOT. If you are near the upper end with a lightly-loaded boat and the plugs are tan, you have an appropriate prop and plugs. Going too hot can burn through a piston. Start with NGK heat range 7. Projected tip plugs will last longer, and resistor plugs will be required in Canada (for radio interference reduction). In the States, we usually run BP7HS plugs.

 

[Sea Rider]

Re: 25 c2 tohatsu id like to run a hotter plug

Ooops, probably a pre Alzheimer inadvertent typo, Correction is not a 30 C3, it's a 30 A3 model.

30 A3 = 4800-5500 wot rpm
30 A4 = 5150-5850 wot rpm

Back to the original question, once modified a 25 C3 becomes a 30A3 or a 30A4 ? Don't have the 30 A3 tech specs so can't tell if same as 30A4 specs ? U don't want to blow that nice engine over revving it at wot as bat out of hell.

Happy Boating

 

[pvanv]

Re: 25 c2 tohatsu id like to run a hotter plug

It becomes an A4.

 

[kajunsquirrelly]

Re: 25 c2 tohatsu id like to run a hotter plug

What's the difference between the br7 and the bp7 the motor calls for a br7