88 johnson 70hp idle racing

[mikew2012]

hi all,

ive read, read some more, and read till ive fallen alseep trying to find an answer to my engine problem.

here goes...

recently bought a be70elcca engine which was in storage for a while, it was easy to start on muffs and idled ok ish.

took it too the water and would not start, (back pressure i assume) we eventfully did start it after putting a little premix down cylinder 2. it started and idled fine. took it for a run and went ok but bogged and lost power intermittently, finally cutting out.

we repeated this process for a good 4-5 times, even let it sit idling for 15 mins and seemed ok, another run and the same thing happened. we came to the conclusion that the carbs need cleaning.

back home we stripped carbs, cleaned all jets (not much crap in there really) and checked float needles and float height, all ok. cleaned them all with carb spray cleaner and very happy with the result.
all ok and clean we refitted it all together.

started 1st crank, now it idles like crazy (but no missing or sneezing) if it were throttled up id say it was perfect running.

but its not, it is idling way way too high, only retarding the timing as far as it can go will it idle low enough that im happy with it.

i have disconnected the cam follower so i know all the butterflies are fully closed.
its pre set mixture with no adjustment screw.

it has the primer solinoid, it used to need manual setting to fire before we took it to the water, but now it doesnt and moving to auto or manuel does nothing.
ive pulled the fuel pump off (not opened it up) and can gently blow and suck the pulse inlet and i can sense the diaphram going open and closed with no leak. it also pumps enough when cranking the engine (we had a clear pipe on it to test.

im running out of ideas now as to what to check, when it did run on the water and behave it was great! now cant get the racing (although smooth racing) idle to come down

plugs were fairly oily when we first got it, now i think its lean as f... the plugs have very little oil on them and when running it is not smoking very much at all. fresh fuel at 50:1 mix as the manual.

sparks all good, flywheel not sheared/spun. TDC is spot on.

 

[durban]

Re: 88 johnson 70hp idle racing

did you undo the screw where the little nylon wheel is on the center carb make sure it doesn't touch the cam see what happens then & adjust accordingly its got a slot in the bracket

 

[mikew2012]

Re: 88 johnson 70hp idle racing

tried that, the roller is backed off the cam follower by undoing the adjusting screw.

I know if it had clean carbs when we went to water it wouldnt be doing this. i have new fuel line arriving today to see if that helps, i inspected them all and found no cracks or splits...for ?5 its worth doing anyway

 

[durban]

Re: 88 johnson 70hp idle racing

check on the other side of the shaft where the butterfly is on center carb starter motor side some 70hp,s have a pin through the shaft i have found in the past that the pin catches the nut resulting butterfly not closing .

 

[mikew2012]

Re: 88 johnson 70hp idle racing

They are 100% closed, i applied a small force against the shaft to make sure.

Really appreciate you helping, ive not been stumped on a 2 stroke to date, had plenty of 125cc bikes and rebuilt most of them, ive got my seagull featherweight, yammie 3.5 aircooled and johnson 25 back up to running fine, this 70 is making me tear my hair out!

never had this much trouble with the 72' 25hp johnson i have, that runs sweet as (almost at the point where im gonna put it back on the boat so i can fish and work on the 70 at leisure)

 

[durban]

Re: 88 johnson 70hp idle racing

normally mine races just before it runs out of fuel i would strip the butterfly's & shaft ,s providing every thing else is set & cleaned , timing excreta ,

 

[mikew2012]

Re: 88 johnson 70hp idle racing

im 99% on it running lean, when i say its racing, i mean its sounds painfully high to the point i want to hit the kill switch.

Ive spoken to 2 marine engineers local to me, they both say air leak or setup wrong. if the idle stop has not been moved, or the idle thumb screw and the butterflies are 100% closed it must be to much air???

Think i might have to bite the bullet and pay the ?38 for the diagnostic check.

one thing really puzzles me, the seller said to run it on 100:1 mix and he seemed like he knew his stuff. bit odd saying that when it took all of 1min to find out it should be 50:1

does this model of outboard have quickstart and maybe its not turning off? some more history on the engine, the seller told me it was a donor engine to make 1 good one out of the 2 he had. the thermostat has been looked at at some point, i can see the blue gasket sealant on the rim. another avenue to check?

 

[mikew2012]

Re: 88 johnson 70hp idle racing

I think i may have worked it out now...

During the process of getting it to start on the water and my brother putting some pre-mix into the cylinder (which i repeated after the carb strip down, just might have added too much) when i was blowing the fuel lines etc to check for blockages, the crankcase hose connected to the airbox was gurgling a little and i managed to get a few drops of fuel come out of it, have i managed to partially interfere with the vacuum process and creating a lean mixture as the pistons arent drawing enough air on the downstroke to draw the fuel from the carbs?

i hope im onto a winner, can anyone confirm it being a possibility?

 

[mikew2012]

Re: 88 johnson 70hp idle racing

Success, its all fixed now.

Took off the throttle cable which i though was stretched, pulled idle back to reasonable level and all is good and steady idle achieved.
ive now discovered my control box is worn, its old so dont think i can source replacement parts unless anyone knows of a good place? it has u.s corp written on it,its black and single lever with no separate warm up lever. it has a button to disable gear selection so it can increase the timing separately. I can take a pic if needed?

during the wiring up of the box, and a nice big spark due to me wiring the whole lot live by mistake, ive killed my primer solinoid.
not in a position to fork out ?90 ish to get a new one so now have a spray bottle connected to the hoses which would prime the carbs. starts easy like this and im happy spending ?1 instead of ?90

now wheres that glorious summer weather gone? this engine needs testing!
im 100% confident with this engine now, should push my little 16ft shakespeare along nicely, hit 18knots with a 25hp on the back.

Durban, thanks for chipping in and giving your advice.

 

[durban]

Re: 88 johnson 70hp idle racing

No worry m8t . happy boating & be safe