1st boat 73 merc 850 wont rev.

[Ghost1958]

First post so howdy to all. Need some help with first bass boat.
82 Astroglass 15.5 ft with a Mercury 73 model 850 85 hp outboard.
Went to see it, it ran on the lake fine.
Brought it home, took it too the lake here.
Launched it. Started it with the fast idle lever up like the guy showed me.
While warming it up my jacket sleeve caught the throttle bumped it into reverse with the fast idle lever up. Went into reverse and stuck there.

Shut it off . One guy came over took the cables off the engine but that was all.
He went and got the marina mechanic. Long story short he shoved the prop with an oar it released.

All worked fine as he hung around while I puttered around the no wake zone.
It didn't want to idle but I blew that off to me not knowing much about it and weather was cold.
Went up the lake motor ran WOT half throttle etc fine. Stopped shut it off. Messed around abit maybe 10 min.

Had to choke and fast idle lever up but started fine. Let it warm up a bit. Lowered the fast idle lever put in forward and the motor wouldn't run over 3600 rpm. Was 5600 coming up the lake and when I bought it.

Been out twice more and it still won't rev up.
Checked spark, good blue fire on all four.
Buying a fuel pump diaphragm kit for it on the marina mechanics suggestion.
I work on motorcycle carbs alot and fairly mechanically inclined but I know diddly about boat motors.
I have checked to see if the the two carbs butterflies are opening up and they are.

Any advise, tips, helpful hints or "you screwed something up dummie", that might point me in the right direction??

Thanks and glad to be here.

 

[jimmbo]

When you were checking to see if the carbs were opening, were you shoving the throttle lever to full throttle, then checking, or was the throttle cable unhooked and you were moving the linkage on the engine?
Have you taken the spark plugs out? If so, what condition were they in? Have you done a compression test since this happened?
I hate to ask this, how much oil and what kind of oil did you mix in the fuel?

 

[Ghost1958]

When you were checking to see if the carbs were opening, were you shoving the throttle lever to full throttle, then checking, or was the throttle cable unhooked and you were moving the linkage on the engine?
Have you taken the spark plugs out? If so, what condition were they in? Have you done a compression test since this happened?
I hate to ask this, how much oil and what kind of oil did you mix in the fuel?

Wife slid the throttle forward while I watched the butteflys.
Yessir changed the plugs though the PO had just put in new ones shortly before I bought the boat.

The new plugs look , well like new plugs, hasn't been run enough to dirty em up much.

Same oil the PO used in it for the 20 yrs He owned it. Quicksilver 2 stroke outbard oil.pint to 6 gal gas like he told me. Tank holds 15 gal.
Thsts 50.1 mix I think?

Havent done a compression check yet. Don't have a tester. I could borrow one though.

Can't figure the compression being bad when it ran like a molested ape until I turned it off and restarted it. Engine doesn't feel weak. It'll jump to 3600 and whatver speed that is quick.
Then just bogs down and holds that rpm. You back off the throttle a bit and it sounds fine just won't rev any further.

The diaphragm in getting is like six bucks so it's not breaking the bank to change it . Just not sure if it will help.

 

[Chris1956]

That motor should have dual fuel pumps on it. Make sure you get the right kits. I do not think fuel pump is your problem. If it was, the motor would rev up to full speed and then drop suddenly.

Compression test is a must. If that checks out, run motor on flusher and listen for spark arc to ground. When the spark plug wires get old, they leak spark.

Last is to rebuild carbs. A service manual is a real good idea, as link and synch is tricky. The carbs are pretty simple. Spray 'em up to clean them, replace gaskets, inlet needle and seat and floats. Manual will tell how ti set float height. Idle circuit has some pinholes in throat of carb. Original floats fail when used with gasoline/alcohol mix.

 

[Ghost1958]

That motor should have dual fuel pumps on it. Make sure you get the right kits. I do not think fuel pump is your problem. If it was, the motor would rev up to full speed and then drop suddenly.

Compression test is a must. If that checks out, run motor on flusher and listen for spark arc to ground. When the spark plug wires get old, they leak spark.

Last is to rebuild carbs. A service manual is a real good idea, as link and synch is tricky. The carbs are pretty simple. Spray 'em up to clean them, replace gaskets, inlet needle and seat and floats. Manual will tell how ti set float height. Idle circuit has some pinholes in throat of carb. Original floats fail when used with gasoline/alcohol mix.

Ok I'll borrow the compression tester from the shop.
What compression should my motor hold?

I probably wouldn't be able to hear spark leaking but I can run it after dark on muffs and watch for leaking spark. Seems to have very strong blue spark on the gap test or though.

I know the triangle shaped diaphragm is what I ordered. Line also goes into a small round gizmo but sure don't look like a fuel pump, though it could be I guess.
I was warned not to get a Mercury by my brother in law unless I knew a Merc mechanic very well.

Maybe I should have listened to him. Lol

 

[merc850]

The little round thing is a fuel filter it should have a screw in the middle to remove it; it's a stainless steel mesh that can be cleaned, did the guy put the cables on the right attachments? If the shift cable is hooked up to the throttle it will speed the motor up but not full. Look at the cables while someone moves the control lever the first one to move will be the shift then the throttle. You should inspect the dist. cap for corrosion and don't try to pull off the rotor it's molded on to the shaft if it looks dirty on the end just touch it with some fine emery paper also the wires screw into the cap don't pull them off

 

[Ghost1958]

The little round thing is a fuel filter it should have a screw in the middle to remove it; it's a stainless steel mesh that can be cleaned, did the guy put the cables on the right attachments? If the shift cable is hooked up to the throttle it will speed the motor up but not full. Look at the cables while someone moves the control lever the first one to move will be the shift then the throttle. You should inspect the dist. cap for corrosion and don't try to pull off the rotor it's molded on to the shaft if it looks dirty on the end just touch it with some fine emery paper also the wires screw into the cap don't pull them off

Thank you. I'll pull that filter see if it maybe stopped up.
And the heads up on the disributer.

The cables are hooked up right. The marine mechanic that helped me get it unlocked out of reverse checked that. They may be a tad out of adjustment, I don't know.

And it ran WOT up the lake right after until I shut it off and restarted it.
I'll clean out that filter in the morning.
Wife wants to go out fishing tomorrow. If it helps it great ,if not we will just run slow and not go very far from the dock so the trolling motor can get us back of it has too.
So far it's never failed to start. Doesn't like to idle and dies at when put in gear sometimes but always restarts and will run about third throttle ok.

Fingers crossed it maybe the filter that I didn't know was there and doubt it's ever been cleaned by the PO cuz he said he just put gas in it and changed the LU once a year and ran it for 20 yrs. Apparently I'm the first to have issues with it.

Would be typical LOL

ETA. Does that filter housing have a gasket I should have before removing it??

 

[merc850]

The idle screws should be set 1 1/4 turns out then with the motor in F in the water at about 800 rpm turn them slowly in and out until the motor runs smoothly then give it full throttle and see if it accelerates smoothly, if not give them a 1/4 turn more. I still think that the throttle is not advancing fully - make sure that the linkage is opening to the "throttle stop" on the plate in front of the distributor. Are you using L77V sparkplugs? I've read the reverse incident and another possibility is you've damaged or mis-aligned something in the control box. Filter housing has an O ring at the base and a nylon washer at the top.
There are 2 tops on the carbs here are some notes but I would check this last

 

[Ghost1958]

The idle screws should be set 1 1/4 turns out then with the motor in F in the water at about 800 rpm turn them slowly in and out until the motor runs smoothly then give it full throttle and see if it accelerates smoothly, if not give them a 1/4 turn more. I still think that the throttle is not advancing fully - make sure that the linkage is opening to the "throttle stop" on the plate in front of the distributor. Are you using L77V sparkplugs? I've read the reverse incident and another possibility is you've damaged or mis-aligned something in the control box. Filter housing has an O ring at the base and a nylon washer at the top.

No buhw plugs NGK brand. That what was in it.
Can you usually reuse the o ring and plastic washer on the filter?.

Yes the disrtbuter turns from Front stop at idle position all the way to rear distributer stop and then pushes that stop on around some more.

I know I'm asking dumb questions but are the idle screw the ones set just to the left of the carb intakes. One each???
Also from the cowling in the fuel lines are secured with zip ties instead of clamps.
If they were motorcycle carbs I'd replace with steel ones but my gut tells me there is some reason for the ties. Just can't fathom what it would be.

Thanks very much Merc850, I'm soaking up as much knowledge as fast as I can.

Sorry for being such a dunce on boat motors but this the first one I ever had or fooled with.

It might be the cables out some but it ran like a raped ape after the reverse incident and cables put back on probably a mile up the lake until I stopped shut it off 10 min.
When I started it back up it was doing what it's doing now. Can't figure what happened with it just floating there not running. Got me baffled.

 

[merc850]

The idle screws are 1/4 dia. and are facing straight out; the high speeds are fixed. Are you saying the lines are clamped to the fittings with zip ties? Not factory and not very secure in my opinion - you can use hose clamps or replace them from here https://store.oldmercs.com/category_s/1702.htm

 

[Ghost1958]

The idle screws are 1/4 dia. and are facing straight out; the high speeds are fixed. Are you saying the lines are clamped to the fittings with zip ties? Not factory and not very secure in my opinion - you can use hose clamps or replace them from here https://store.oldmercs.com/category_s/1702.htm

Yessir. The hoses bulb etc look brand new. PO said the bulb was new.
But from the fitting that goes inside the cowling all the hoses are zip tied instead of clamps.
I can easily replace them with regular steel hose clamps If there is not some boat motor only reason not too??

 

[Ghost1958]

Update on the Merc 850
Went fishing today. Marina mecanic used to work at Mercury dealership.

Adjusted my cables. Which were out some.

Have no reverse.
Fished anyway. Did find crack In the onboard fuel filter that seeps fuel.
Also one stator wire connection is green and almost broken where they go to the voltage regulator.

So putting an inline filter in the line and bypassing the onboard one.

Will fix the stator wires. Hopefully that gets me WOT in forward. I'll use the trolling motor when I need reverse and run it until I can afford to fix reverse or get another motor.

 

[merc850]

The stator/rectifier only charges the battery it doesn't run the ignition. The shift cable end should be in the middle of the slide (near the edge of the block) when in neutral and at the far end for reverse; when the motor is running watch the end when someone shifts the control into reverse and see how far it goes - if it doesn't go all the way back give it a push to the end which should put it into R. If it goes all the way and the LU is still not in reverse then the problem could be the upper shift shaft or the shift cam or the LU hasn't been installed correctly. When was the waterpump impeller changed? does water come out of the hole in the cowling on the right side of the motor?

 

[Ghost1958]

The stator/rectifier only charges the battery it doesn't run the ignition. The shift cable end should be in the middle of the slide (near the edge of the block) when in neutral and at the far end for reverse; when the motor is running watch the end when someone shifts the control into reverse and see how far it goes - if it doesn't go all the way back give it a push to the end which should put it into R. If it goes all the way and the LU is still not in reverse then the problem could be the upper shift shaft or the shift cam or the LU hasn't been installed correctly. When was the waterpump impeller changed? does water come out of the hole in the cowling on the right side of the motor?

Yes sir. It "pees" well.

The mechanic took off the shift cable and kept turning the prop with his foot while he found F, ,,R

He said something about a reverse shift dog or spring that probably got damaged when I had my initial fast idle reverse episode.

I'm figuring the cracked onboard fuel filter is letting to much air in. Hopefully that will stop the bog problem. Have to choke it if it sits more than 10 min.
I'll fix wires cause they need it and not a huge deal to do.

It HAD reverse when I bought it. Think I probably busted it that first day.

If I can get it to rev in F I'd be happy.

The guy adjusted the cable a LONG way and it doesn't hang and die when it's moved to rev postion now. Just no reverse.

 

[Ghost1958]

Oh the mechanic isn't charging me for anything yet. One of my closest friends daughter works there so I'm getting "family rates " for now.
But adjusting the cables and getting me unlocked that first day is all he's done.

In your guys opinion will it hurt anything to ru, the boat in F, forget R and just use the trolling motor when I need reverse??

Assuming I can get to WOT in F??

 

[merc850]

You can run in F only but you should have N too for safety, I've worked on many Mercs and this is weird; the image below shows how the shift is done - the shiftshaft turns CCW to push the shift dog into the reverse gear then CW to go back to N;F those are tough parts and can take a lot of abuse. Reverse has a lot of tension on the shift mechanisms but F only has spring tension holding it.

 

[merc850]

If it were my motor I would drop the LU and see if you can shift it by turning the shiftshaft CCW do not pull up on the shaft or you'll pull it out and have to disassemble the LU to repair - and grease the driveshaft splines at the top when reinstalling.

 

[Ghost1958]

You can run in F only but you should have N too for safety, I've worked on many Mercs and this is weird; the image below shows how the shift is done - the shiftshaft turns CCW to push the shift dog into the reverse gear then CW to go back to N;F those are tough parts and can take a lot of abuse. Reverse has a lot of tension on the shift mechanisms but F only has spring tension holding it.

Thanks . I do have N and F but no reverse.

I spent the afternoon working on it.

All the bakelite insulation was crumbled 9n not stator wires. Cleaned them off, they are a braided copper cable. Got them cleaned up the pushes shrink tuning up each wire to its base at the stator and shrunk them.

Replaced the ends.
Put a new filter in to bypass the onboard one that is cracked
Found a screw loose that acted as a hinge point for the bottom carb choke plate. Fixed that.

Pulled the distributed cap.
It had an oily film in it . No idea why.

Cleaned the cap contacts lightly and the rotor button.

Checked to see for sure that the carb butterflies are wide open with the throttle WO.
At the moment pulling the LU is 1. A bit beyond my know how right now.
2. Beyond my finances to put parts in anyway right now.

I'll try taking it out again tomorrow. Hopefully it runs in forward like it should.

After this all I would know is a fuel bulb.

Wife pumped the bulb last time we were out while I held it WOT no change so I'm guessing the pump is ok.
Thanks for hanging with me on this guys.

 

[Ghost1958]

Update on haunted mercury 850.

Took boat out today. As soon as I was out 9f the no wake zone hit the throttle and she took off like a raped ape.
5600 rpm settled it back to
5000 ran a good 3/4a of mile purring like a kitten.

Saw another boat fishing backed out of It so I wouldn't hit him with a big wake. Slid on by him , pushed the throttle forward and 3000 is the best it would do.
Actually backing off the throttle would stop the bogging and get it run steady at 2700.

Marine mechanic had me being it over to marina shop, put muffs on it.
Fire is good. Diaphram on fuel pump good.
Fuel pressure is low. Top crankseal leaking so motor isn't producing enough vacuum to operate the pump diaphragm to keep up at high revs.

Best I can find out pressure should be about 3 to 5 psi. So I'm bypassing the whole fuel pump and bulb and putting a 3 to 5 psi electric fuel pump inline to see of it will WOT on it.
If it will I'll take the pump off the toggle switch and wire it to come on with the key switch.

Ah well I had a grin a mile wide this morning for about 5 min before it bogged out again LOL

 

[merc850]

The top seal has to be replaced or the cylinder will run lean because there won't be enough pressure or suction to feed it; should be fixed before anymore running and what about the lower seals? You're going to be jury rigging this motor for however long it lasts and a lean piston won't last long. I bought an 850 and took it apart before I used it to check on all the seals bearings etc. it's been running hard for 6 summers and I get 8 mpg.
The seals can be replaced without opening the crankcase - seals are cheap and easy to replace.