The newer 40 hp sounds sharp, of course you've got the leak around the cylinder block cover. Just a cover with a gasket, leaking around the spark plug holes is common. Don't force any of the cover bolts when you tear into it; they'll break right off. Better to apply heat to the side of the bolt and work it free. The 40 probably needs a new impeller, has a week telltale. Of course the leak isn't helping water pressure much, is it!!
The 35 sounds sick, like it's only running on one cylinder. Needs compression check, spark tested, hard to say.
BTW it's really difficult to tell anything about how any outboard runs without putting it in a "bucket". They can sound great on a flusher, but without exhaust backpressure of being in the water, symptoms of poor running can be masked.
So run 'em in a barrel and see how they sound. You can idle them in gear as well, get 'em warmed up and then adjust idle mixture and speed. The 40hp is idling way too fast, unless you just had it throttled up. Best to not run 'em at such high speeds out of the water, it's hard on the rods, pistons, and bearings.
A Big Thank you, tons of very good info
I will be careful removing those bolts thanks, it is missing one to begin with
i did replace the impeller last year and have only had it running for a few seconds, here and there, as it had other problems. no spark, for one, finally replaced the trigger and then a problem with the magnet coming loose. Well is was not loose but slid next to the other magnet under the flywheel ( i guess that could have been the no spark situation also but i could get a spark when i fooled with the trigger wire. And i will think to adjust the throttle speed in future testing and try to get a bucket to test in
I will check those items on the 35, i could kind of hear a pop every now and then
i will have to do some reading and watch vids on mixture and idle speed
Master Ed-Mc is correct in that proper back pressure is needed, and is best presented by running the beast in a barrel of water - rather than on the muffs.
Based on the video's sound, and my deaf ears,...I am not convinced that the 40 is running on both cylinders.
The simplest test regarding this is to:
Start the beast with both spark plug wires connected to their respective spark plugs.
Then turn the beast off, and remove one spark plug wire.
Once removed,...Be sure and plug a spark plug into this loose spark plug wire, and rest it against engine ground to avoid unnecessary stress on the related ignition components.
Attempt to start the beast. IF it starts,...Does it sound the same?
If it doesn't start,...Put that plug wire back on its respective spark plug, remove the other spark plug's wire, put a spark plug in it, and rest it against engine ground to avoid unnecessary stress on the related ignition components.
Then see if the beast starts.
If the beast starts and sounds the same as it did when you set it up to only spark on the other cylinder,...You can believe the beast is firing on both cylinders.
If the beast refuses to start on one or the other cylinder while one is disconnected,...You have discovered that the beast is only firing on one cylinder.