1980 90hp, dies when put in gear, idle to high

[JonNovak]

dies when put in gear while in water only. on hose it shifts fine. cant get the idle any lower than 1,200. in order to move in water i have to rev it then shove it in forward once its warmed up. if not warm enough itll stall out within a blink if an eye.

on hose i cant get the idle lower than 1200rpm. itll stall out then be hard starting again if i try to go lower.

has new coils and wires from previous owner. i just put new plugs in it.

the first time i had it on the water i figured there was a carb problem. found one float full of gas. ordered 3 floats, and 3 sets of inlet needles, seats and seat gaskets. also carb gasket sets.

put it all back together not moving the carb idle screws. pump in fuel and find hoses now leaking. purchased all new gas lines and used metal hose clamps.


still can not get idle lower and still stalls soon as i put it in gear while submerged unless i rev it up first.

i now have setup a barrel to run the motor in the garage so i dont have to keep pulling it out to run it

ive searched and there are 3,000 opinions, one as silly as regulator/rectifier was the cause of the problem

i got this motor cheap and was all good except bottom end was warn pretty good from being run with water in it. replaced bunch of stuff down in there plus water pump. so i dont have a lot invested and dont mind fixing a couple things here and there, but im not gonna spend 1k at a shop to fix something that is probably gonna be just that one simply thing i could test or rebuild.

i have a 25 mariner on my little'er boat and that was a vacuum leak at the carb. SIMPLE, but it drove me nuts for a month untill i figure it out


---------- i am interested in hearing what i should do next but must also mention, since i have it in the back of my mind, that i might want to pull the jets and make sure its all clean in there just for peace of mind? The motor before i got it didnt sit more that 1 year. the carbs were very very clean and the guy said it ran fine when removed from boat. the thing that made him remove it was it didnt go into reverse anymore. it wasnt a cable, it was the wear on bottom end parts! No lube, just water!

gonna add stuff as i remember:
EDIT 1: New fuel filter
EDIT 2: just found bearing oiler line to top of powerhead is cracked and leaking. parts list it as (HOSE, BALANCE-MAIN BEARING) Pulling electrical mounting board to replace those lines and inspect further.
EDIT 3: NOPE, its listed as 2 check valves and bleed hose. the main bearing hoses are behind carbs. probably check those real good too

[JOE54]

if it has idle stabilizer undo it , check all linkage throttle shutters closed completely , try air mix screws 2 1/2 turns out

[JonNovak]

motor has a date written on top of power head in grease crayon. maybe from factory. appears motor is now a 1983
not sure about the idle stabilizer thing. ill look into that
ordered fuel pump rebuild kit. replacing broken hose today. will check all the throttle stuff before next fire. i had set everything up so butterflies open to 90 degrees at wot. they stopped short before. looked like they closed 100% but will check into all that to be sure.

idle screws originally positioned at
top 1 1/4 turns out
middle 2 1/8 turns out
bottom 2 1/8 turns out

i played with these. turning into to lean hearing rougher idle. then out half turn. most of the time motor stalled out and had to reset back to original working thru hard starting issue.

[JonNovak]

no idle stabilizer on this motor. parts list and diagrams show it never had one from factory.
started it up other day and now my tach on dash stopped working. pulled tiny tach off other boat and will be hooking that up. also pulled rectifier off other boat since this one seemed to be no good. might also have to test stator.

my stator has 2 red wires going to rectifier. i have a known good 5 wire stator/rectifier laying around. i wonder if i can hook the 2 red wires from stator into the yellow wires of the 5 wire stator/rectifier?

watched a video today about reeds not sealing and misty gas/oil mix being shot out from carbs at idle creating a bad idle problem. will also looking closely at this idea

[JonNovak]

pulled all the idle screws out, cleaned in each hole and the needles themselves. reset to 2 1/2 turns out, later adjusted out another 1/4.

reset all the butterflies to 100% closed. adjusted the butterfly roller cam to not touch the actual cam. moved throttle to decrease or increase the switch. got her started and played around with switch position. got it to a good lower idle, runs for a minute then chokes out. i thought i had it too. was nice and low in 700-800 range

adjusted the throttle roller after advancing the switch into its travel and can run forever at 1400rpm. drop to 1200 or anything below that and itll idle for a minute then stall.

verified rpm with my TTO tach since onboard tach no longer works. known good stator seems to be working but no charge at low rpm as expected with a battery thats not fully charged. battery now on charge for the night. still shouldnt see much a charge at low rpm i think, but whatever on that

sometimes this motor will fire and putt putt putt nicely for 2 seconds then jump in rpms to 1400. i have a feeling whatever is causing this is causing the whole problem.

i dont know where to go now. waiting on fuel pump kit but dont think thats gonna solve it

[JOE54]

I had one doing this to me also long time ago, labyrinth sealing area on reed cages were worn out , my opinion mtr not worth it

[JonNovak]

why, are they expensive or tough to change and seal new ones? i only have 500 into this motor. 200 purchase. plus 100 in gas to go get it, plus couple in parts so far, mostly bottom end stuff to bring that back.

i dont mind throwing a little more at it. has great compression and with a few more $$$ and experience gained i will have a good time out in the tidal river over winter and spring catching schoolie stripers

i am on the lookout for another 90, but i have time to kill while i collect more pennies

[JOE54]

complete disassembly required , they are part off crank assy,may not can get them from merc anymore , and yes they are very $$$$$$

[JonNovak]

rebuilt fuel pump. old diaphragm didnt look to bad. inside was very clean.
open idle mix screws 1/4 turn each. bypass (new) fuel filter since it seemed to empty without staying remotely close to full, still.
primer bulb fuel line direct to fuel pump. tinker a bit with spark advance linkages and idle.
got idle lower but will only stay running if i keep the primer bulb full and stiff. one i stop, itll run a minute then stall. pump bulb and its soft. pump bulb hard, crank and start takes a tad bit of work.

seems to me this is fuel related.

i got the idle down to 700-900-1100-1200 bouncing all around those numbers on the tto tach. but i can tell its idling lower and mostly stays in the 700-900rpm range if i continue to pump the bulb so it stays stiff

could the fuel pump possibly not be getting vacuum?

Oh yeah, brand new primer bulb fuel line setup.

[JonNovak]

yeah so ok, keep pumping will idle lower. stop pumping and itll die in 30 seconds to 1 minute. crank crank crank nothing. crank crank crank while squeezing bulb and once firm itll fire

[JonNovak]

every time i have to pump it back up before itll start again i can hear the top carb filling but not the bottom 2

[billnorman1]

I don't have a Mercury or know much about them. Idle speed is usually controlled by the amount of air going into the motor. If you have enough fuel mixed with the air it develops power. Any air source like a leak between the carburetors and the cylinders will let air in that has no fuel with it. Also a carburetor that has no fuel or the fuel is not mixing with the air will run fast but not develop any power. Some old Mercs with multiple carburetors ran on one carburetor and as the throttle advanced it picked up the rest of them, one carb was all they used at idle.
If you had an issue with the lower unit and it was not properly reassembled it can stall the engine either at idle or when put in gear because the driveshaft is connected to the L/U and always turns if the motor turns. If it binds up the motor won't run properly. You could test this by taking off the L/U and seeing if it runs well for a short period of time but not long or it can overheat.

[JonNovak]

Tube, Idle !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!

thats what parts list this as. parts i couldnt get to last time. i almost gave up again. i just about ruined the screw trying to take everything out of one of the carbs then found a wrench screwdriver and i could get all the red locktite screws out. pulled this long thing out and was a bit gunky on the top. whipe it off and realized its a tube. parts list call it "tube, idle"
blew thru it and now i can see thru it.

im going thru each carb over again more thoroughly this time.


i also ran the bulb soft (let it stall), pulled the carbs and the top had a little less fuel in it than the bottom 2.



will report back once i get all this done.....couple days.. renewed motivation

[JOE54]

make sure check valves in fuel pump are good and new gaskets installed

[JonNovak]

check valve certainly is working in fuel pump via the mouth blow suck test. fuel pump was rebuilt with a kit, all new gaskets and diaphragm same order it all came apart. but i did just re-tighten all the bolts holding it together. seems i never tightened them down very good or after heating up on the last running in barrel they needed to be re-tightened .... not sure but i think that wasnt a good thing .....

carbs all done and back on except the top carb i ended up pulling the throttle roller. has a small flat spot and im going to replace that plastic no longer available piece with something else. have a few options lined up ill tinker with at the shop tomorrow.
all three carbs set to 2 1/2 out. only one idle tube seemed to be gummed up and clogged. other 2 didnt look to bad. little gum around tip but not clogged.

lots of fuel in reed areas. motor does seem to smoke excessively. fresh fuel on 50:1 mix

so, i also was thinking maybe because the bleed hose was broken, and for who knows how long (only ran the motor on the lake twice since buying it in july), the crankcase has so much built up fuel causing some related problems with the excessive smoking. wot on the lake it didnt seem to smoke that much but wot is usually a different animal. both times on lake and using wot the bleed hose was cracked not knowing.

tomorrow ill be trying to fire it up and see what happens. probably run a tank of fuel into the river this weekend and see how it all goes. if nothing gets better i may have to take that lower end advice. if i get to that ill end up rigging a cold water intake so i dont worry about running time

thanks for checking in and replying. 2, 3 and 4 brains are better than one

[JOE54]

always

[JonNovak]

how the %&#% am i running out of fuel. same deal as before. pump firm while running will idle nicely. stop pumping and its running out of fuel. with motor off i pump it up as hard as i can and get no fuel coming out of anything.

ive tried running with fuel tank cap open before but im gonna try it again. dont think itll change. im stumped


edit: im gonna get the straight gas out of my portable tank and put some mix in that and try that !
maybe ive got an air leak in the onboard tank where its sucking air. there is a line from tank to nipple then another line from other side of nipple. ugh

[JonNovak]

no dice. motor keeps running out of fuel for some reason. how much crap do i have to rebuild twice?

maybe i did something wrong. it wont even keep a high idle now without running out of fuel in a minute. wonder if i should try to find a whole fuel pump assembly

[JonNovak]

gonna try to put a T fitting in fuel line after fuel pump with shut off on each out of the T and run the motor then switch over and see if fuel pump is sending fuel out.....if i can find all the parts in the shop tomorrow.

guessing it wont be pumping so ill be then pulling the pump and seeing what might be wrong within it or behind it at the 2 pulse holes

sure beats hanging around in the house watching tv all the time :\

[JOE54]

remember fuel pump works off of crankcase pulse an internal leak (reed cages leaking psi internal ) no pulse or weak