89 Evinrude 40hp only goes 10mph 3k rpm

[kaivorth]

Long story short. Bought a 17ft Bass Tracker with the Evinrude 40hp motor. It's sat for a year or 2. I've dumped the old gas, installed a water fuel separator, and filled the tank with ethanol free gas with 50:1 ratio of Pennzoil 2 stroke oil.

Compression is 100psi at 1 cylinder and 110psi the other cylinder. I didn't warm the motor up doing this.
Brought it out on the water, and will ONLY start when it starts to catch, and I quickly put it Wide Open Throttle.
When she's running, she will stall at low RPM
She will only go 10mph, 3k rpm
She will temporarily boost to 20mph, 4k rpm when pressing in the key, I believe this is the choke? Sounds like it's fuel restricted.

This should be hitting 30mph easily.

I've ordered a carb kit to rebuild and clean the carbs
Going to get new spark plugs
Going to change the gear oil
What's the best way to inspect the fuel line for blockage? Giant rod?

I also brought this to the marina. He said the motor was junk, it failed his leak down test. Again he didn't warm the motor up. Was 10% one cylinder, 20-30% other cylinder. I'm suspicious that the motor isn't junk, as he tried to sell me a 30hp Johnson he had there.

Am I on the right track to get this going again? Or am I fighting a losing battle?

 

[jakedaawg]

That's low compression

 

[Bosunsmate]

You could put some atf fluid in the spark plug holes and sit her up to see if thatl loosen any stuck from carbon rings.

 

[kaivorth]

So just trim as high as I can make it go, and squirt atf fluid in there? How much for how long and what to buy?

Is this motor a lost cause?

 

[Bosunsmate]

Enough to cover the piston domes thoroughly. Leave as long as you can. If it was me id disassemble and check the rings and clean them out but try ATF if it disassembly isnt for you. Different people have different recipes to try but i find atf is good
Nope not a lost cause so long as you dont give up on it

 

[kaivorth]

I'm not familiar with small motors but I'm pretty mechanically inclined.
How much work is it too disassemble and check the rings? I can do this with the motor on the boat right?
And should I be trimming up all the way to get the motor horizontal when leaving atf or seafoam in there?

 

[Bosunsmate]

Piece of cake if not a salty. Two to three hours. You will need to pull off the flywheel with a puller of some sort.
yep trim her up

 

[RCO]

I am a professional mechanic, and I do not put a lot of faith in cylinder leakage tests in 2 stroke engines. Check the compression. If they are within 10% I would say the motor has proof of life. Sounds like you have a carb issue if I were to guess.

 

[boobie]

Agree with the above 100%.

 

[Bosunsmate]

Oh yeah if 100 and 110 is alright psi for that motor then im wrong and would suspect carbs too.
I had thought 140 might be the correct psi for that motor but quite possibly its not

 

[kaivorth]

Update:

So I've messed with a lot of the throttle linkages while I'm looking at this whole thing. Going to order 2 bushings that the throttle rolls on, and also a new intake gasket. I've rebuilt the carbs with no improvement. When I rebuilt the carbs, I did notice a lot of hard gunk that I couldn't really get off of the bottom of the bowl. Going to go buy a Gunk Carb and Parts Cleaner, and dunk the carbs in that overnight as well.

I'll remove the carb gaskets and float while doing this, can I leave everything else in there as is?

The "fuel mixture" screw outside of both carbs are now at 2.5 turns from the bottom. Should I play with this? They were at 3.25 and 4 before, seemed wrong from everything I've read so I made them both 2.5

I've also just replaced the gear oil. That stuff was nasty.

I've just added seafoam to the cylinder heads through the spark plug hole instead of atf. Seafoam seems more common for this but I could be wrong. Sprayed a whole can into both spark plug holes. Going to let it sit a day or 2, in hopes to bring compression up a bit more. This should still be running halfway decent with the compression numbers as is I think.

To remove the excess seafoam in a day or so, do I just unscrew the spark plugs and turn it over a couple times?

 

[kaivorth]

Rebuilt the carbs again. This time dunked in Berryman Chem Dip Carb Cleaner overnight. There wasn't much residue, it's just a somewhat rough casting.

With the carbs rebuilt, I will rebuild the fuel pump tomorrow, and give an update this weekend. I will also recheck compression throughout the weekend.

Stay tuned.

 

[kaivorth]

UGH. Same issue. Only stays running nearly WOT. I'll mess with it more tomorrow. Going to play with the air mixture screw that's on the side of the carbs. What woulds this be at approx? I'm at 2.0 turns.

 

[juno pierrat]

any improvement in compression? if not, maybe time to remove head for inspection, and a new head gasket can't hurt

 

[kaivorth]

Brought it to a different Marina. It was just an ignition coil!

It wouldn't idle so I couldn't pull one while running. Engine was just running on one cylinder.

I guess if I pulled one and tried to start it, it would've either done nothing or start the same way and stall out.

Taking the boat out this weekend. If I dont report back, that was definitely it.

Learned a lot about small motors from taking everything apart though!

 

[kaivorth]

Another update:

Boat would only go about 20mph WOT which was a big improvement, but it should still be hitting almost 30mph.

Last owner broke the fuel manifold, and decided to tee the lines together instead of replacing it properly.

After playing with the throttle linkage so both carb throttle plates are perfectly horizontal at WOT, new fuel line, new fuel intake manifold, she got about 28-29mph, much better!

I have a new aluminum prop on the way now. I expect to hit about 32mph hopefully. Old one is all chewed up.

Also plan to move both batteries to the rear of the boat where the fuel tank is, properly vented, to help with weight distribution to plane faster and easier. Wiring job is a mess currently.