Dial-a-Jet on an outboard

[berg969]

i was searching on the web and came accros This (http://www.thunderproducts.com/dial_a_jet.htm) . anyone had any experiance with it? do you think it would be benificial or just a waste of money?

Thanks All,
Evan
http://www.thunderproducts.com/images/photos/dialajet2.jpg

[Dean Dorsey]

Evan, I have run them for years in my mod. mountain sleds, and I swear by them, They give better fuel econ. and better snap off the bottom and mid due to the better fuel atomization. I used to have to re-jet almost every weekend depending on where I went, for the past 2 yrs. have not re-jetted my sleds once and can ride from 1,500 to 10,000 ft and from 15 degrees F. to 60 degrees and keep the EGTs just where I want them . I have always wanted to try them on an outboard, but have only EFI motors. I would bet they would work well on O/Bs as well. You need to do some carefull testing to determine your baseline jetting. EGTs are a must when using them. Good Luck, Dean

[berg969]

dean,
how much adjusting did you have to do on them, and how much is done by the dial-a-jet itself
Evan

[Hottrucks]

Its probablly a good idea for sled heads I'm one myself! But our or at least my boat is run at the same (?) altitude and about the same temp ,most of the time unless your looking for that extra little bit or know what your doing leave it or you'll have a pile of nice cooked parts next to your computer to look at!!! Dial ajet is great but it's easy to forget to fatten it up on a cool morning and end up running lean!

[berg969]

the only reason i was thinking of using it is i am always switching props (from 17p to 21) and jetinmg is a nightmare because i only do it for top end so i figure this will be allot easier than having to change jets all the time

[Dean Dorsey]

Evan, Good question each has I believe 6 enrichment settings they are easy to install would require drilling and tapping a set of threads for each carb I believe about $30 per carb. Remember d-a-j will only richen the mixture but your initial jet decision should be just a size or 2 at most leaner than normal. Point was made about burning up with these a ligit. concern if you jet to far down or dont use egts. What I can tell you from personal exp. is that it seems to give a much greater range W/O adj. than a standard jet. I have not burned down with sleds since I started using them, where before I got pretty good with a hone and acid. The fuel saving alone would make it worth while. One of the main advantages of the D-A-J is the greater atomization of the fuel which will feed the motor more efficiently on less fuel or less waste, also much less plug fouling or loading also plugs will look different leaner ask Thunder. I have also used their UFOs for round slide carbs with great success, but these really do require a great amt. of carb setting knowledge to make them work safely, many others feel the UFO are junk. Since Thunder products is primarily a snowmobile company I would call them and ask for referals and initial settings for your motor. This is the one product I believe can really help with minimal risk other than foolish jetting by the owner, again because they can only richen from initial jetting. If you do install these find a setting that is moderately lean on a cool day with your smaller prop not to exceed 1200 degrees WOT this should cover you with both props in most all temp cond. W/0 any further adj. if adustment is needed it takes about 30-45 seconds per carb. Dean

[berg969]

thanks for all the info. i was thinkking of puting the dial a jet onto the horn that way the carb wont be permanently affected

[Dean Dorsey]

sounds like a good plan, i would mount them as close to the carbs as possible. If each v. stack supplies 2 carbs you will need 2 dial a jets per horn should be mounted as directly as possible in the air path of the carb venturi tube. You will need access to each carb bowl as low as possible for the fuel draw tube for the D-A-J, this line should not be kinked as it goes from the carb bowl to the mounted dial a jet. If a route for that fuel tube cannot be located without kinking, or fuel drawing point cannot be located within the bottom quarter of each carb bowl I would not do the project. Just some thoughts. Dean

[berg969]

its a 3cyl 50 hp yamaha thats been very modified. i went from 32mm carbs to 38mm not to mention porting and displacement

[Dean Dorsey]

One unit per horn should work fine, your carbs are roughly the same size as I have been useing them on. DD

[Markus]

Berg969, we tried mounting Dial-a-Jets at carb throat like you suggest, but they did not deliver any fuel. They need a pressure differential; I guess they get that because there is an air box on a sled or motorcycle.

When mounting them in the venturi, they do actually work, but we swapped to a set of big bore carburators before being able to tell if there was a performance increase from the Dial-a-Jets.

[berg969]

Markus

wouldnt there be a pressure differential if the dial-a-jet is on the carb with the horn?

[Robert]

Hey Guys,
It takes 4 inches to prime the device and it will operate down to 1. Markus is dead right on the signal problem. I will warn you that if you don't have the required signal and start jetting down, you can misinterpret an rpm gain for a fuctioning DAJ.

One of the board supertuners mentioned a signal of 4.5 with the butterfly's closed down to .100 at WOT. Since you can't remote mount behind the butterfly and I don't think the device will work at that low of a signal, it won't work.

It also needs to be 90* of airflow, even 1* off will affect function.
It's a great idea thought up by an acoustic engineer that set over a hundred records from the drags to Bonneville on a bike.
Dr. Dennis Dean

Hope it helps

BTW Mine are mounted less than a 1/4 inch from the butterfly and not enough signal. 91 225 Looper