36 year old 35hp motor maintenance

[191 champ]

I posted a week ago about issues not starting. Well, it runs fine now. The scary part is that I don't know why. I don't think it was ignition related. I did check the spark with a tester and it was good. I checked the idle timing now that its running and it seems fine. I didn't change anything in the fuel system from what was previously done. I'm still thinking a stuck Reed but don't know.

Regardless, I had already started some maintenance on this fairly new to me motor and had planned to replace the stuff mentioned any. My question is what else should I do for a motor this old

So far I've:
Replaced all vacuum and fuel lins, including the one from the tank, rebuilt the carb and fuel pump. I didn't change the wech plug so shoot me. No used gaskets or other parts were used.
Changed the impeller kit and lower unit oil.
Replaced the plugs.
Greased all the zirk fittings.
Inspect all of the wiring. Found a couple issues and fixed them for now but will do more.
Cleaned the starter gear with brake cleaner and added a dry film lubricant. This actually helped as the starter was a bit sluggish before.

I plan to replaece the thermostat.
Replace the Reed valves just because they are so old.
Decarbon the engine. Right now I'm just running stable in the gas. I may do a stable shock treatment but would like to know if this is safe.

What else would you do?

[ChampioNman]

A shock treatment with Stabil will do nothing for the motor, you should perform a decarb with either BRP engine tuner or Merc Power Tune. Model number always helps when posting motor inquiries.

[191 champ]

Thanks, I'll get some and do this instead.

[bighare]

You are on a good path. Decarboning the cylinders and rings will make a big difference on this engine. Recommend an over night sit in the tilted up position to get the best results.
The double fuel shock treatment may not see benefits since you have already cleansed the major components.
Cranking speed is important for starting. If the starter rotates too slow the magneto does not build sufficient electrical power for ignition. Believe it or not the a good tug on the rope starter, if you have this, will build a faster rotation.
The reed valve pedals are arranged in a circular pattern. One set for each cylinder. It would be unlikely for these to stick closed.

Now let my next suggestion be guided by the idle quality as this fix requires removal of the power head. The exhaust pipe / exhaust tube inside the exhaust housing and attached directly to the engine block directs all exhaust down to the lower unit. This tube also includes strategically placed and sized exhaust relief holes for improved idle quality. These holes are known to plug with carbon over the years. Plugged idle relief holes result in a less than perfect idle quality especially at slow speeds. Cleaning them is not a critical requirement but if you have difficulty finding a good idle mixture adjustment, with the boat floating in the water, you may wish to take the step to pull the powerhead, remove the tube and clean out the holes. An additional benefit is to inspect the impeller water supply tube. The tube is connected to the exhaust tube and block via a rubber grommet. This grommet deteriorates over time by heat and gets restricted by corrosion. The result is reduced water flow causing a high speed overheat.
good luck.

[191 champ]

You are on a good path. Decarboning the cylinders and rings will make a big difference on this engine. Recommend an over night sit in the tilted up position to get the best results.
The double fuel shock treatment may not see benefits since you have already cleansed the major components.
Cranking speed is important for starting. If the starter rotates too slow the magneto does not build sufficient electrical power for ignition. Believe it or not the a good tug on the rope starter, if you have this, will build a faster rotation.
The reed valve pedals are arranged in a circular pattern. One set for each cylinder. It would be unlikely for these to stick closed.

Now let my next suggestion be guided by the idle quality as this fix requires removal of the power head. The exhaust pipe / exhaust tube inside the exhaust housing and attached directly to the engine block directs all exhaust down to the lower unit. This tube also includes strategically placed and sized exhaust relief holes for improved idle quality. These holes are known to plug with carbon over the years. Plugged idle relief holes result in a less than perfect idle quality especially at slow speeds. Cleaning them is not a critical requirement but if you have difficulty finding a good idle mixture adjustment, with the boat floating in the water, you may wish to take the step to pull the powerhead, remove the tube and clean out the holes. An additional benefit is to inspect the impeller water supply tube. The tube is connected to the exhaust tube and block via a rubber grommet. This grommet deteriorates over time by heat and gets restricted by corrosion. The result is reduced water flow causing a high speed overheat.
good luck.

Awesome input. I never would have thought of this sort of thing. Sounds like a good winter project. It seems to idle okay but then, I have no idea what perfect is.

[bighare]

The 35,25 hp at 32 cuin was never the best idle quality. Especially for trolling. Nothing beats the 9.9 or 8hp.

[OK_BassBum]

If the reeds are bad, you should see some gas being spit out through the carb.
You can use a flashlight to help you see this. Sounds like you got everything when
you went through the carb and fuel system. Have Fun!