85 hp Blue band motor stalling when going into gear

[bluesilver]

Hi, I have a technical issue that i am now completely stuck on ideas on what is causing this particular issue.
I picked up a second hand boat and motor, only just recently have had the chance to take it out for a run.
The motor is an old 1976 -1977 85 hp Mercury Blue Band motor.
The issue is when you fire the motor up when in the water, it will idle ok, but as soon as you put it into gear, either forward or reverse, it will stall the motor.

What i have done so far is remove motor from boat, removed the prop, then sat the motor in a large drum of water.
The issue goes away, as in it will go into gear and run with no issues, looks like the issue is when the motor is under load with the prop on.
Compression is good on all 4 cylinders, spark is good on all 4 cylinders and also the correct firing order.
There is no timing pointer, so i have found TDC and made one up from a piece of wire, running the motor with a timing light, i can't even get it close to when the timing should be, looks to be firing way too early, but sounds ok.

Only thing i have found so far is when removing the flywheel to check the trigger plate, i did notice that the number stamped on the trigger plate is 96451, i did a search and it tells me this is a trigger plate for a 50 hp Mercury.

I am completely lost no for any ideas on what is going on with this motor short or from taking it to someone to find out what is going on.

Any ideas would be greatly appreciated.
Cheers.

 

[racerone]

Believe it or not !!------This is a common issue with these motors.----Believe it or not the fix may be as simple as opening the low speed mixture screws a 1/4 turn at a time.-----Often the problems goes away with no coins spent.----Try it !

 

[jimmbo]

Just how and at what rpm are you trying to time the engine? The 85hp and 50hp both have 4 cylinders, and may use the same trigger plate

 

[bluesilver]

Thanks for the replies, appreciated.
I was trying to to get a tune with it at idle, just before it stalls, unfortunately the device i was using to see the rmp s has decided to play up not getting accurate or true readings, tried to see what the timing was like as revs increased, but not even close on the timing maker on the fly wheel.

The trigger plate might be ok then, hoping it was.

Haven't played with the needle settings yet, figured it could play up with keeping both carburetors in sync with each other.
Just has a quick look to see where the low speed needle was, looks like there is only the one needle to adjust without removing them, ( it is the one on the right hand side ) both carburetors have them set different, one is flush, the other out at least 1/2 turn more. I think this is the low speed needles you are referring to?

Is there a good easy way to sync the carburetors up myself?

Really appreciated the help and information.
Cheers again.

 

[racerone]

????----Turn those needles in and GENTLY seat them.-----Turn them out 1-1/2 turns.-----Put boat into the water.-----Adjust those needles in equally until motor stalls on acceleration.-----Turn out until motor is happy.----That will likely correct the issue with no money spent.----I guess that seems to be too easy

 

[Chris1956]

It is also best if the carbs are clean. If in doubt, remove, clean and rebuild with new gaskets. If inlet needles are suspect and if floats are the original foam (versus hard plastic), replace as well. Then follow Racerone's procedure to adjust the idle mixture.

 

[bluesilver]

Cheers again for the replies, appreciated.
Found what you was talking about with the low speed needles, thought you was talking about some other needles that i couldn't see and adjusting, resetting them will be easy enough to do.
Is there a way to actually balance the two carbs to get them in snyc with each other, or just tune by the sound?

I am yet to figure out why i can't get the timing marks to line up as per the manual in section 6-25, 6-26
But going with the good advice on here, will remove and completely dissemble the carburetors, clean and check float levels.
Put the timing back to how it was, then start with tuning the carburetors.
Then go from there.
Cheers again.

 

[Chris1956]

The synch of the carbs is done by making sure they start to open at the same time. On top of the bottom carb linkage, is an adjustment for this. Loosen the screw, and preload the bottom carb so it opens with the top carb..

The plastic linkage can get twisted, so it needs to be adjusted every once in a while.

I can help with the timing adjustment, if you provide your issues.

 

[bluesilver]

Cheers, The carbs are pretty well working together, so that part is all good.
I currently have to motor off the boat and is on a stand, prop is off and have the leg sitting in a plastic drum full of water.
Both carburetor setting were way off as was advised, nearly a full turn on one and 1 and a half on the other.
Set them both at around 1 1/2 turns and motor seams happier, but this is still in the drum with no prop.
Still has a while to start sometimes and likes a lot of throttle, but reading through the posts, his seams to be normal.

Timing, i have got the low revs part set i think at around 2 degrees, just not sure on the rmps as the ebay device i had isn't working too well.
Think i am trying to get the revs down too low while trying to this and keeps stalling, thinking most of the issue is that i have it in the drum and really needs to have prop on, mounted on boat and in water at this stage, or maybe it can be done in the drum, not sure.
Should i be trying to get the timing right before playing with the carburetors?

 

[racerone]

did you remove the flywheel by removing the 8 bolts ?-----Note----Timing on these motors rarely goes out of adjustment.-----Make sure you understand 2 stroke timing before making adjustments.

 

[bluesilver]

No, i just removed the center lock nut and then made up my own thread and then made the puller, it is exactly the same as the Mercury outboard pullers you by, just cheaper to make it myself.
The flywheel has a large flat area on the shaft, so it can;t go back on in a different way which is good.
Won't get the motor back on the boat for a few days now to give it a test run, bit of luck the issue was with the carburetors.

 

[merc850]

Are you setting the low speed needles with the boat in the water at 900rpm - in forward gear - (underway?) this is the only way to do it.

 

[bluesilver]

I have with the motor sitting in a large drum of water with the prop off.
But i am thinking this is only a rough setting and need to put the motor back on the boat and take it to the water as you mentioned.
I am thinking because the motor has no load on it just sitting in the drum with no prop the settings will change a bit.
Plus i need to find another good tachometer to use.

 

[jimmbo]

900 rpm in gear, is too high of an idle speed, 600 - 650 is more realistic