87 50hp running issues

[Jdills1371]

Long story short. Evinrude 90 went bad. Got my hands on an 87 Yamaha 50hp. Fresh gas, fresh oil, new plugs, carbs taken apart and cleaned really well.

Starts up fine. Runs for about 10 seconds and dies out. When con*****ing the throttle by hand while it’s running. It acts like it wants to try to get hung up and run wide open on its own. Then it dies out.


Any help would be much appreciated.

[Jdills1371]

[99yam40]

I have a feeling you did not do a link and sync after putting the carbs back on.
do you have a service manual for that motor?
very good idea to have one if working on it

and opening the throttle plates without advancing the timing will give you that type of response

[Keithbaja]

Ummm, as a pro with over 40 YRs in DA biz. link & sync along with timing almost never, EVER needs to be messed with. Don't listen to wanna bee's. Your description sounds like your running out of fuel. But I would suggest you try to describe your motor symptoms again.

[99yam40]

do not listen to him either, even the Yamaha service manual calls for link and sync after putting the carbs back on every time

[Keithbaja]

Yam fool, you don't do this for a living now do you,, I don't even remember the last time I had to do a link and sync.. And its always after a weekend warrior messes it up. You are a old fool that lives on this blog and don't know crap about outboards.. Get a life!

[ausnoelm]

Ouch, that hurts.......might need a group hug I think.

[ausnoelm]

Ummm, as a pro with over 40 YRs in DA biz. link & sync along with timing almost never, EVER needs to be messed with. Don't listen to wanna bee's. Your description sounds like your running out of fuel. But I would suggest you try to describe your motor symptoms again.

I find it interesting that someone with over 40 years experience, meaning you are "mature" would ever type "DA biz"

[Jdills1371]

Ummm, as a pro with over 40 YRs in DA biz. link & sync along with timing almost never, EVER needs to be messed with. Don't listen to wanna bee's. Your description sounds like your running out of fuel. But I would suggest you try to describe your motor symptoms again.

I thought the same thing as well. Out of fuel. But as soon as the motor dies out, I can immediately turn it over and it fires right up for another 10 seconds and dies. Fuel line is good. Fuel runs thru it fine. Unless once motor starts it’s collapsing the line and I can’t see it.

but also after reading these responses. I’m still at a loss. Link and sync. Don’t link and sync. Or just go drop it off at the dump.

[TownsendsFJR1300]

It's a "new" engine to you so you don't know the history of it.

With ANY used engine it'd be wise to go over the engine overall (timing included) as you know, over time, many PO's / "mechanics" touched / adjusted things on the engine.

Fix the issues and enjoy.

.

[99yam40]

what does it hurt to do the link and sync as the manual calls for,
the motor has never run properly for you.
when I get my hands on a old motor , compression, spark. and timing are all checked.
link and sync is done too if I had never done that myself just to make sure everything is in spec

and as I said before opening the throttle plates without moving the timing advance will not let the motor spin up properly.
believe who ever you want and do what you want

and I agree, you need to explain better
what exactly does this mean

" When con*****ing the throttle by hand while it’s running. It acts like it wants to try to get hung up and run wide open on its own. Then it dies out."

[TownsendsFJR1300]

" When con*****ing the throttle by hand while it’s running. It acts like it wants to try to get hung up and run wide open on its own. Then it dies out."

This, ^^^^ bolded, sounds like the engine running out of fuel, you get a high idle, then stopped engine.

If the throttle plates are closed when RPMs rise on their own, no air leaks at other times (weird running), it's a classic running out of fuel..

.

[99yam40]

only things I saw on his videos was him pushing the throttle plate linkages without including the timing linkages

this is what I do not understand
It acts like it wants to try to get hung up and run wide open on its own

[Keithbaja]

Wellll, I could not get audio on your video, and on this little screen (dumb phone) I assume you have REAL boat motor as in two stroke. Which if you Jab the throttle without advance timing will do what your sorta describe. Almost all two strokes advance ign timing for fast idle.. Not moving throttle plates. A little unknown fact. Linc & sync all you want. What the hell no harm done. Its very,very seldom timing and carb syncing needs to be done on a outboard.. I get calls all week about getting a "Tune up" on outboards. Is no such thing.. What, plugs these units are designed to RUN and unless some yahoo messes with the factory setup or cam follerer gets worn there is NO issue. You have not produced your running issue correctly. PLEASE give more info.. Have you test run boat on DA water ??