Need help on evinrude 7.5 hp 1957

Adjusted carb as instructed, runs fairly well can't get to idle down much below shift speed, checked compression both cylinders checked 65 psi. Maybe why slow speed will not go any lower ,high speed will rev real high when it's not in gear,when you put in gear and put a load on it max rpm will not get up to same level at full throttle sounds like it wants to but just won't go . I can only get 12 ft john boat to go 6mph per gps with both my son and myself in boat. Tried with just me in it same thing, will not go fast enough to get it to plane down. What do you think? Compression,timing,points,carb setting. Chain saws I can figure out first time with an outboard.

Thanks for any help

First, You shouldn't be winding that poor little motor up in netrual unless you want to be wearing pieces of it permanently embedded in your hide. The rods on that motor won't take much of that. Try adjusting your hi speed knob (1/4 turn increments) while in gear and running WOT on your boat. 65 psi is pretty low compression. Sounds like it's just tired.

As majkmann said 65 is a bit low but in your favor the readings are even. Recheck with another gauge. Check that the throttle/mag plate linkage is synched to the carb. That would be the roller wheel that rides on the advance plate just above the carb. Might also have to adjust the motor tilt on the boat.

(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)
Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:
NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, waiting for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.


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