What the heck are these?

[NMShooter]

I'm installing a tach on my boat in prep for fishing this weekend. I've only used this boat on no-wake lakes, and purchased it used three year ago. I've never had the boat at full throttle, mostly just trolling. Maybe that is a good thing, although the previous owner used it for tubing.

I boat at 5000 to 7500 feet here in NM. I am going to Arkansas this summer and will be at about 1000'. So I thought I might take a look at the jets to see what the jetting orifice is. I have heard that if I am too lean I can fuse a piston.

Here is where it gets weird.

My motor is a 1988, 85 HP Force. From what I have found on the web, this is what the jetting should be :

for 0-2500' F10212 0.074"
for 2500 to 5000 F10213 0.072"
for 5000 to 7500 F10214 0.070"
for 7500 to 10000 F10215 0.068"

Carb kit probably FK10125

How do I check the orifice size for the main jets? Do I need to remove the carb bowls to do so?

What are these things on the side of the carb? They are stamped 058.

 

[Frank Acampora]

Re: What the heck are these?

The main jets are inside the bowls. The "jets" you have arrows pointing at are actually metered air bleeds. They are exactly the same as the high speed jets except the orifice is much smaller--in this case .058. That means that the diameter of the hole is exactly .058 inches in diameter.

Yes, going down in altitude will supply denser air to the engine, there will be more oxygen to burn, and the engine will run lean.

Take off the carb bowls and check the high speed jets. If they are not .074, buy a set of three and install into the carbs. Use a GOOD square-tipped screwdriver that fits the slot correctly. Those jets are in tight and will "crack" when they finally break free. A poor or improperly sized screwdriver will slip, ****-up the slot, and possibly damage the orifice.

Note that different engines used different model carbs with different jetting--sometimes in the same model year. If the jet size you find is not what you expected, take the model number off the carb mounting flange (example only: WB 24) and use that to see what size jets are required.

With the extra power developed at low altitude you may also be able to--or even need to use a prop with a higher pitch. If you are using a 13 X 17 now and running near the top of the rpm range, (5500) you may need a 13 X 19

 

[NMShooter]

Re: What the heck are these?

Oh BTW... I have a 13x19 pitch prop and a 13x15. I figured the 13x15 for here, and 13 x 19 for lower. That's also why I am installing the tach, so I can see what my WOT rpms are.