Logo
FULL SITE MENU

Screw Missing in throttle body!!

N

Nytro-Gylcerin

New member
Just purchased 1981 Johnson 20 (same as 25),

Cleaning the carb today and realized one of the two screws holding the flapper on is missing...

I just bought the motor and have only heard it run breifly in a barrel. Havnt checked compression yet. Wondering if this screw if Ingested would make it all the way through and cause damage, or if there is somewhere it would likely settle and I should look????

No idea if someone simply took the carb apart and lost that part, but I doubt it, I would assume its come loose and gone into the intake.

Help please, outboard newbie here. Not new to motors though, just no idea where this instake system leads too, as its opposite the cylinder head!

Picture attached.



Thanks
IMG_2877.jpg
 
If the compression is good on the motor, I'd run it. That screw could be long gone having been spit out the exhaust.
 
If your 20 is like my 85' 20 the intake is restricted and smaller opening then the 25's and up and the screw likely may not make it into the intake.Not sure if it could be laying down inside around the reeds or not?Got a dental mirror?
 
Thats what I wondered. Thanks Boobie! I looked in the cylinders and there isnt any visible damage. Do you think theres somehwere it may have settled and may come free later down the road?

thanks for your advice. I will test compression tommorow, any idea what numbers I should be looking at for an 81 20HP? Accounting for wear and tear and it being that old... ?
 
I do have a dental mirror, ill give that a try. The intake is resticted as well, except its restricted on the lower half of the throat, so anything laying in that area would be free to fall down into the intake.
 
That screw will absolutely fit through the intake. If it goes through the motor very seldom do they go without wrecking anything. Take the carb off and look in the reed plate hopefully it is stuck in there. You have 2 choices run it hopefully the screw is not in there. Or take the motor apart and look for the screw to make sure it's not sitting in there somewhere. The tear down gives you peace of mind and will cost about $50 if you do it yourself. The run it method is everytime you go out you will be thinking about the screw. If it is in there it will cost you much more than $50. Your call
 
Yeah. I could take off the intake plate, and look at the reeds. If it went past the reeds, would it not be either in the cylinder or already passed through? is there anywhere along the intake it could settle? Im used to snow machines where after the reed it goes right into the cylinder...

Im assuming ill need a new gasket if I take that off. Is there any torque specs for that intake plate?
 
Found that on a 135 hp many years ago.---Stuck in the reeds.----Found the same thing on a big twin, stuck in the reeds
 
That screw would either have made it to the related cylinder and have been blown out the exhaust port... OR... more likely, be jammed in the related reed plate's leaf valve.

Best to remove the intake manifold in order to inspect that reed plate properly as that small screw could be quite difficult to see if it's laying in there. Guessing could be expensive!
 
I think I will test compression and if its normal, take off the intake plate and look at the reeds. Any idea where I can get the torque spec for the bolts/nuts on that intake?

thanks everyone!
 
The torque specifications in that area?.... I was dead serious with my work for over 30 years but never once paid any attention to the torque specifications in that area... just tighten them. Head bolts, crankcase bolts, connecting rods, flywheel nut, gear-case area, etc..... yeah, that was another matter and we took that seriously.
 
Just pull the intake and look at the reeds and into the crankcase.I doubt it would make it past the reeds and almost sure it would not make it to the piston/s. Worst senario is it got ground up in one of the main journals and the metal fragments would damage the seals as well. If it was mine and the screw was not in the intake I would split the crankcase and give everything a good visual now. All it will cost is a few gaskets and some time. Being a 36 year old engine you may want to deglaze the cylinders and put new rings in while you have it apart and give everything a good eyeball. You should get another 30 years.
 
compression is 110 & 118, but that could be a little inaccurate as I didnt really pull until it leveled out I just made sure they wernt way different.

Going to pull the intake now, I assume ill need to buy new gaskets for this. My model is the 81 20HP which ive been using thye 81 25HP parts for since its not really a motor thats in the parts system. Would the intake gaskets be the same between the 25 and 20? I would think so!

Thanks all.
 
well, took off the intake and the reed plate, no screw to be found. I really dont know if its worth going all the way and tearing the whole unit down for something thats likely either passed through or ground up. I could flush the crank with gas through the open intake??
 
Back
Top