drilling for larger jets

[cobiawayne]

installed boysen reeds on my 97 merc 200.My manual says stock sizes are 82 and 80.What size drill bits would I need to get 86 and 84?The reason i:m asking is I seem to be running about 20 degrees hotter

[Scott in MN]

You're better off just ordering the jet size you need.......20 degrees doesn't seem like a big difference.....If you look at drill sizes they tend to jump several jet sizes so it is hard to accurately drill to all jet sizes.....I've heard that reamers are a better solution but more expensive....

[cobiawayne]

Thanks Scott, I"ve orderd them from my merc dealer,but they wont place the order till they have the 300.00 minimum order stacked up.I"ve learned here about the consequences of runnin lean and I sure dont want to screw up.

[john j 80 viking]

I know its done all the time, but drilling jets is tricky because of the scratches that are left in the orifice, if you drilled one out to say 85 it wouldnt flow like a factory 85, try one of the vendors on s+f its great to have lots of jets to choose from for weather changes, rule of thumb is one jet size for 10 degrees :mad:do we have to look at these disgusting teeth on the computer screen:mad:

[Scott in MN]

When you say 20 degrees hotter do you mean EGT temps or water temps (I assumed EGT)?????
20 degree increase in water temp would concern me enough not to run it........
20 degree increase in exhaust temp is negligible...don't know how you would read it unless you are using a digital readout......

[Dave Strong]

installed boysen reeds on my 97 merc 200.My manual says stock sizes are 82 and 80.What size drill bits would I need to get 86 and 84?The reason i:m asking is I seem to be running about 20 degrees hotter
Most times I have never had to rejet when installing Boysen reeds, but at 2600'+ stock jetting is a tad rich. If any thing needs to be changed it's normaly the idle jets, 1 size richer(smaller). If I remember they tend to run richer on the mains.
But lately my memory hasn't been so good. Haven't played with carbed motors much lately.
Dave

[cobiawayne]

The 20 degrees is water temp,its around 165 @ 5000 rpm,water temp right now 83 in the river

[Scott in MN]

What was river temp when it was running cooler? Hard to imagine a reed change producing a 20 degree difference in water temp. I have run jets to the extreme and never seen a change that large......I will see a 20 degree change from spring to mid summer but the lake changes 20 degrees.

[sschefer]

.086 is a number 44 drill there is no standard drill bit for .084 you would need to have one made. In order to drill the jets accurately they would need to be done on a calibrated end mill. The runout on a standard drill press would be enough to throw you way out. Easiest way is to buy if you can.

Edit.. Stock jets are good to 5000 feet according to Merc. Fuel quality changes would be the only reason I would consider it. Just run 89 gas and you should be fine.

[Dave Strong]

What is water press? I agree with Scott, can't see it being a jetting problem. I know up here, water temp in spring 45-50deg, summer it can get as high as 80deg. What temp guage? can you compare with " lazer style" most electric temp senders are not real accurate.
Dave

[WATERWINGS]

.086 is a number 44 drill there is no standard drill bit for .084 you would need to have one made. In order to drill the jets accurately they would need to be done on a calibrated end mill. The runout on a standard drill press would be enough to throw you way out.

Huh?

I do it with a hand drill, and hold the jet in a socket with the jet still in the jet screw....DAMN THE TORPEDOES.....FULL SPEED AHEAD!!!!!!!! :D

[YELLOWSS]

i have drilled a lot of them over the years.. if you are talking about egt temps running hotter you need some bigger jets.. i have drilled them before... find a drill bit that will just clean the jet up. you dont need much. that should do it. those are popular jet sizes. should b able to get some used ones on here.
if you are talking about water temps you have other issues. check water pump.

[WATERWINGS]

You can get drills that aren't fractional sizes, they are "letter drills", (A,B,C,D etc.), and they cover some of the jet sizes.

I have a little plastic box that I keep my jet drills in, and, correct me if I am to far off, but the drill decimal size is the same as the jet number, .082 for instance.

That is what they measure if you pick a jet that is stamped .082, that is what it also measures.

I have heard that something is special about the factory jet having a taper(?) or something (?), but I have never noticed a problem that I could tell, by doing it my way.

[cobiawayne]

Thanks guys for all the replys, I think maybe i"ve figured out whats going on,Took my boat out this morning its a 1971 seacraft 20 sf with an enclosed transom and a 31 inch stainless marine bracket.25 inch leg on my merc 200 and i"ve got my motor adjusted as high as it will go(its up there)I don"t have a water pressure gauge,but i,m going to get one because my intake holes I believe are catching air.I gutted the thermostats and its doing better(brand new waterpump)If I remember right I believe I raised the motor up 2 holes the same time I was changing reeds.I.m going to make some adjustments and i"ll let yall know the outcome.This morning it ran 155 degrees at 4700 rpm and about 120 at idle.Thanks again.