force 120/125 40 over pistons Jet size

[ForcedError]

87-95 force 120/125. It's a bit of a Frankenstein. I had my block bored .040 over and matched pistons. I'm usually boating around 650' above sea level and I don't want this turd to lean out. What size jets do you fellas recommend and is there a difference for top and bottom carb? It starts, runs and idles very well but not winding it up too much until break in and jetting takes place. Thanks in advance. You guys know your stuff!

 

[Jiggz]

At 650' above sea level all you need is the standard jets. Over boring cylinders does not require changes in carb jet specs. Sure there will be more air passing through the carbs because of the over sized bores, but that is also metered by the carbs. Meaning with more air passing through the carb, the more fuel will be incorporated.

Now above 1500' above sea level requires changes in jet size due to thin air or less O2. FYI, changing the jet size (smaller actually) does not compensate for loss power due to low O2 but only to prevent fouling due to rich mixture.

 

[jerryjerry05]

What block did you use? the 87 is a different bore than the 95
What carbs did you use? from the 87 or 95??
The 4 different carbs 2 top 2 bottom all used different jets??

To test: Get the motor running, run it at wide open for 5 minutes.
Then reach over and turn the key off.
Don't throttle back or pull into N just shut the motor off.
Then pull the plugs and check the burn.

 

[ForcedError]

Thanks for the response fellas. That brings me to the Frankenstein issues. I bought the boat recently from a guy that knows nothing about its history. It's serial number indicates it's an 87 125 hp. The casting of the block does not have removable covers for the fuel recirculation system. It did however have 3.375 bores that I punched out to 3.415" due to 8 broken rings and some ugly pistons and cylinder scoring. The pistons old and new are bottom guided. After beating my head against the wall for weeks trying to find a noticeable miss caused by the prestolight ignition system, I yanked my entire ignition system off my 95 force 120 and threw it on this Frankenstein. Problem solved. The carbs on it have no markings of manufacturers unlike the tillsons on my 95. The bottom carb has 061 as part of the serial number from memory. If you need actual serial numbers I can grab them.

 

[Jiggz]

The standard fuel jet sizes are as follow (sea level to 1500' elevation):
Top Carb - 0.0937
Bottom Carb - 0.101
This with the standard issue carbs which are all the same for the 87~89 125 HP.