Evinrude 7518

Hey guys I've made a post or two but just wanted to make an updated one since I still haven't found the root of my issue. I have a 1955 Evinrude Fleetwin 7.5 that runs and pees, good spark that jumps 1/4" and 80psi in both cylinders. I am having an issue where it sometimes will not go into gear, and when it does, it won't shift under load. My feeling is that it's some combination of a carburetor in need of a rebuild, and a gear case malfunction. Gear oil was not milky when changed but was extremely dark and pasty, carb jets are extremely hard to tune and do not work according to factory presets, which i believe is 1 and 1 1/2 turns for low and high rpm jets, respectively. Thanks for any advice you have or links to carb kits or lower unit parts you can provide.

If engine rev’s and no-go in gear, check drive pin on propshaft - or perhaps spun prop hub bushing.. good luck!

Doubt there is a rubber drive bushing in a 1955 prop.

I don't know what point you are at but may as well drop the gc and do an inspection and change impeller . check shift linkage components from shifter to LU

try LU shift changes manually when finished with impeller. your shock absorber may need an inspection ( below WP housing) ...if extended a few spot welds back to size and a brass drive pin will do.

Carb should have no bearing on shifting unless you can't get the idle speed low enough to shift. What is the ebgine rpm when your shifting? No guessing here, need an accurate tach reading. Pasty gear oil is not a good sign, the older stuff was dark and a little thicker than today's gear oil, but pasty ? Perhaps a good clean and flush of the gear case is in order.

racerone said:

Doubt there is a rubber drive bushing in a 1955 prop.

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Crosbyman said:

I don't know what point you are at but may as well drop the gc and do an inspection and change impeller . check shift linkage components from shifter to LU

try LU shift changes manually when finished with impeller. your shock absorber may need an inspection ( below WP housing) ...if extended a few spot welds back to size and a brass drive pin will do.

Click to expand...

airshot said:

Carb should have no bearing on shifting unless you can't get the idle speed low enough to shift. What is the ebgine rpm when your shifting? No guessing here, need an accurate tach reading. Pasty gear oil is not a good sign, the older stuff was dark and a little thicker than today's gear oil, but pasty ? Perhaps a good clean and flush of the gear case is in order.

Click to expand...

I already put a new impeller in, and I believe I have two separate issues when shifting. The idle rpm is possible to get low enough to shift but only the big knob affects it and its crazy sensitive, has to be in the absolute perfect sweet spot, only about 1/4 turn, to shift. This leads me to believe the low rpm jet is clogged or damaged as its knob is useless.

The other issue is in the gearbox, as the shift knob will just not move forward or backward as if the F and R gears aren't there. Its usually fine, but sometimes seemingly at random it will decide only neutral exists.

I had both these issues overcome by a combination of pure luck and perfect carb jet adjustment and it was propelling both directions in a bucket. When I got it on the water, I couldn't get the knob tuned to lower the idle rpm enough to shift without cutting engine, although it was shifting into gear.

airshot said:

Carb should have no bearing on shifting unless you can't get the idle speed low enough to shift. What is the ebgine rpm when your shifting? No guessing here, need an accurate tach reading. Pasty gear oil is not a good sign, the older stuff was dark and a little thicker than today's gear oil, but pasty ? Perhaps a good clean and flush of the gear case is in order.

Click to expand...

I also do not have a tachometer but will look into acquiring one

fleetwinner said:

I already put a new impeller in, and I believe I have two separate issues when shifting. The idle rpm is possible to get low enough to shift but only the big knob affects it and its crazy sensitive, has to be in the absolute perfect sweet spot, only about 1/4 turn, to shift. This leads me to believe the low rpm jet is clogged or damaged as its knob is useless.

The other issue is in the gearbox, as the shift knob will just not move forward or backward as if the F and R gears aren't there. Its usually fine, but sometimes seemingly at random it will decide only neutral exists.

I had both these issues overcome by a combination of pure luck and perfect carb jet adjustment and it was propelling both directions in a bucket. When I got it on the water, I couldn't get the knob tuned to lower the idle rpm enough to shift without cutting engine, although it was shifting into gear.

Click to expand...

Since You are having issues with Fuel Mixture Needles, is the Float buoyant. and adjusted correctly?

You say sometimes the Shift lever won't move, is the Motor running when this happens?

The Mixture Needle are not use to adjust or set Idle Speed. Spark Timing is what determines the Idle Speed
Is the Synchronization between the Carb and Spark Advance correctly set?

Are the Points gapped correctly?

fleetwinner said:

I also do not have a tachometer but will look into acquiring one

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Lots of portable tachs on the market for little money. Shifting rpm is usually down around 600 rpm...

Have you been to AOMCI yet? You may find that crew helpful for parts.