I am posting this for a friend and I will send him the link - any thoughts are welcomed! Thanks so much!!
I have a stock 1987 J300PLCUR and a stock 1985 E275TXCO on my 25? Cougar.
The 300 is running rich. It has a sooty exhaust and black smoke on the prop.
The 300?s carburetor is a 394699, which should have: 36, 42, 78D jets, but has: 28, 20, 80D jets in it (Idle bleed, Intermediate bleed, main jet).
The 275 seems to run fine. The prop hub and exhaust are clean.
The 275?s carburetor is a 397479, which should have: 30, 36, 65D jets but has: 28, 20, 65D jets. Both motors have the air silencer covers, but no baffle in the air box.
The BRP catalog shows a different parts number for the crank case and cylinder heads for the two engines (ref:1987, Evin, 300, diagram). I thought the gain in horsepower was made by increasing the rev limiter to 6100 to 6700?
1. Is there a mechanical difference between these engines (higher compression ratio)?
2. Is there a difference between the 275 and 300 that requires different jetting if both motors are propped to run the same RPM close to 6250?
3. I?ve included some info from BRP catalog below. It seems they settled in on 48, 42, 71D for the 300s but I don?t know if internal changes were made to carburetor body? Please feel free to make a suggestion on the proper jetting for these motors.
Year Hp Carb assy Carb body T body Idle air | Inter- | High
bleed | mediate | speed jet
1985 275 394698 397576 397577 36 42 65
1985 275 379479 397578 397579 30 36 65
1985 300 394699 397576 397577 36 42 78
1986 275 397357 397574 397581 33 29 62
1986 300 397339 397574 397581 33 22 80
1987 275 398407 398069 397581 33 29 62
1987 300 398408 431938 397581 33 22 80
1988 275 398367p 432512 397581 48 36? 60
1988 275 398358s 432512 397581 48 36stbd 60
1988 300 398349 432512 397581 48 42 71
1989 300 398349 432512 397581 48 42 71
1990 300 398349 432512 397581 48 42 71
1991 300 398349 432512 397581 48 42 71
1992 300 398349 432512 397581 48 42 71
1993 300 398349 432512 397581 48 42 71
1994 300 436545 436014 397581 48 42 71
1995 300 436545 436014 397581 48 42 71
I?m planning on changing the 300?s main jets from 80D to 71D to get rid of the smoke on the hub and dry up the spark plugs.
I?ve read a lot of articles on S/F about reading pistons and jetting. I know I?m running rich. I?m looking to take the next step to get closer to the factory setup. Any advice is greatly appreciated.
I have a stock 1987 J300PLCUR and a stock 1985 E275TXCO on my 25? Cougar.
The 300 is running rich. It has a sooty exhaust and black smoke on the prop.
The 300?s carburetor is a 394699, which should have: 36, 42, 78D jets, but has: 28, 20, 80D jets in it (Idle bleed, Intermediate bleed, main jet).
The 275 seems to run fine. The prop hub and exhaust are clean.
The 275?s carburetor is a 397479, which should have: 30, 36, 65D jets but has: 28, 20, 65D jets. Both motors have the air silencer covers, but no baffle in the air box.
The BRP catalog shows a different parts number for the crank case and cylinder heads for the two engines (ref:1987, Evin, 300, diagram). I thought the gain in horsepower was made by increasing the rev limiter to 6100 to 6700?
1. Is there a mechanical difference between these engines (higher compression ratio)?
2. Is there a difference between the 275 and 300 that requires different jetting if both motors are propped to run the same RPM close to 6250?
3. I?ve included some info from BRP catalog below. It seems they settled in on 48, 42, 71D for the 300s but I don?t know if internal changes were made to carburetor body? Please feel free to make a suggestion on the proper jetting for these motors.
Year Hp Carb assy Carb body T body Idle air | Inter- | High
bleed | mediate | speed jet
1985 275 394698 397576 397577 36 42 65
1985 275 379479 397578 397579 30 36 65
1985 300 394699 397576 397577 36 42 78
1986 275 397357 397574 397581 33 29 62
1986 300 397339 397574 397581 33 22 80
1987 275 398407 398069 397581 33 29 62
1987 300 398408 431938 397581 33 22 80
1988 275 398367p 432512 397581 48 36? 60
1988 275 398358s 432512 397581 48 36stbd 60
1988 300 398349 432512 397581 48 42 71
1989 300 398349 432512 397581 48 42 71
1990 300 398349 432512 397581 48 42 71
1991 300 398349 432512 397581 48 42 71
1992 300 398349 432512 397581 48 42 71
1993 300 398349 432512 397581 48 42 71
1994 300 436545 436014 397581 48 42 71
1995 300 436545 436014 397581 48 42 71
I?m planning on changing the 300?s main jets from 80D to 71D to get rid of the smoke on the hub and dry up the spark plugs.
I?ve read a lot of articles on S/F about reading pistons and jetting. I know I?m running rich. I?m looking to take the next step to get closer to the factory setup. Any advice is greatly appreciated.