Hello all!

[DoubleD99GS]

Hey guys,

My names Dennis, im 21, and I've been reading the forum for the past couple weeks. Finally got my account validated and now I can post! First off I just wanted to say how great the forum is. Learned a ton already!

At the moment I have a Jerry Dunlap 27 that my dad and I built, with a Thunder Tiger .21 outboard that im very happy with, but my need to modify stuff is driving me to do a whole lot more with it. I know we already have a couple experts on the TT engine here, so im really looking to learn from you guys.

I guess the areas where I have the most questions is in the area of sleeve modification and timing etc. If someone could point me in the direction of some sort of basic intro to sleeve modification or gimme a little walkthrough on some improvements i can make on the TT sleeve that would be excellent. I'm planning on turning down the head button (or buying one if someone has one) and installing a pipe (also if someone is selling a pipe let me know... I'll make it fit)

So yeah, Just wanted to say hello and hopefully get my foot in the door with modding the boat! Let me know what you guys got!

-Dennis Ladendorf

 

[waltr]

Welcome Dennis.

We're happy to have you aboard.

You'll find more information on this site than you'll know what to do with along with a great group of people.

If it's Thunder Tiger info you need, Jerry Wyss is the guy that's the TT Master. He goes by the same name on I/W and the TT in your header will probably catch his eye anyway.

Good luck!

 

[Jerry Wyss]

Hi Dennis, Walt was right, them double "T's" always catch my eye. A pipe is the right direction with this motor

and the best available is the HTB Silver Bullit "HP". The total weight of the TT o/b is a few oz's heavier than most

of the others so cutting the muffler out will get rid of some weight. There are some post's that I have on here that

show how I cut them out but some of the pics have been deleted. If you need more help with that , let me know.

The stock button is a big fault with this motor but the stocker can be cut down to work pretty well. You can mod these

motors to where the JD WOF won't handle it but just modding the button and raising the exhaust port, with the pipe,

K&B1L plug on 60% will be allot of fun.

The header I use is an Ofna product part #10060 , I buy them at Tower Hobbies,, you'll end up cutting off most of

the last part of the "L" (90* bend) shaped part of the header. (Note: Tower hobbies doesn't use that Ofna 10060

part number) You'll have "Browse by category", click on "Engines & Accessories", scroll down to "Engine RC Components",

click on "RC Engine Headers/blah/blah/blah" find Ofna page, last thing on the list "Ofna Manifold.21 W/spring Polished"

Any other questions, just ask,

Jerry

 

[DoubleD99GS]

Thanks much Jerry! Glad i caught your eye pretty quickly.

about machining down the button... The actual squish area of the button shouldnt need any sort of modification from stock should it? I can understand cutting down the whole outside around the button to achieve a smaller piston/head clearance, but i was just curious as to if you cut down any other part of it.

I was reading some older posts that talked about head shims and sleeve shims and such, and I was curious what was the story about that. Is that what you are talking about when you are saying raise the exhaust port?

also a pic of how you cut out the muffler would be awesome. I can see pretty much where I "should" cut but it would be good to hear it from someone that already has cut them.

Where is the best source to obtain an outboard pipe?

Thanks for all your help!

-Dennis

 

[Jerry Wyss]

A bunch of different ways you could go with the stock button,, at first I took enough off the bottom

of the button that sit's on top of the sleeve flange to give me .006" head clearance,, that would be

a depth (part that goes into the sleeve) of .115. It's best to remove the entire surface of the side

that seats on the sleeve flange instead of trying to cut that channel thats in there,, you can do it

that way if you can, it's just allot harder.

I kept the angled squish at first but took it off too later just to get the volume lower. At that time

I didn't know about propper heating of these smaller o/b's, if I had known I'm sure I would have

gotten much better results with the "cut stock" buttons. This engine (and many like it) have to run

fairly hot to get the rate of burn right, specially with the greater volume they have. I pull the water

off completely, at a rich setting, run the boat several times, working the needle in. You get near

200*F (pulling the boat outa the water and shooting the plug with a heat gun) and its going to

come alive. Like I've said before,"take a tip from the cars guy's", they run theirs between 180

and 250*F,, the races use the latter mark and sometimes a little more.

Sleeve shims will increase the open time of all the cylinder ports, .020" will get the intake ports higher

than you would want them and the exhaust port roof will still be .030" short of getting in the low 180*'s

so thats where cutting that up more to where you want (or need it) comes in. I don't think the low 180's

is what you want to be using with the "still" higher volume of the cut stock button,, this is also a game of

keeping the compression ratio from getting too high or low.

It needs to be mentioned here that adding sleeve shims will require an increase in that ".115" figure in the

first paragraph in proportion to the amount of shim you use.

Another thing, the crank window will have to have its open time increased or the benefit of what you done

with the sleeve ports will not be realized. This work is not that difficult for me, I know how much and where

material needs to be removed and can have the crank opened up in a 1/2hr, honed and ready to go.

All this will have to be kept in a certain area of mods or your 27" boat will be flyin' outa the water all the time.

I have something in mind that will probably work better than what I was running on a 27" boat. I can do all

the engine work in my sleep and have located an existing "after market" button that could take the TT right

to the front and may even work well with the muffler on!

JW

 

[Jerry Wyss]

Dennis, Here's a pic of my cut-out style, you'll notice the area in front of the exhaust nipple the needs

to be hollowed out to clear the header cup.

 

[Tim_Duggan]

Dennis,

Jerry will point you in the right direction.

If you aren't familiar with cutting ports in a sleeve - I'd suggest you might want to get someone "in the know" to do it for you. Only takes one little slip and it's toast. Sleeve shims and custom head button will get you part of the way there, but the exhaust port will need to be raised to take advantage of a pipe.

My modified TT ran a SPP NR21OB pipe. The Aussie guys on here can tell you how it performed.

 

[DoubleD99GS]

Wow man, thanks so much for all the info!

Sleeve modifications are something i would leave to someone else for sure, though eventually it would be awesome to be able to do it on my own.

As to the comment about the angled squish... With the head button out of my boat the squish looks to be totally flat, with a spherical bowl in the center, with no sort of angling that i can tell. Maybe im looking at the wrong thing, maybe not. Also I saw that you mentioned something about an aluminum head shim on the stock button, but i cant really seem to find one. unless it is just wedged into the slot where the sleeve goes. in that case i have no idea how to remove it.

I really would like to run a pipe on the boat, but your idea with the aftermarket button would still work alright with a pipe correct?

Sent you a PM as well Jerry.

Thanks again!

-Dennis