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1978 mercury 800 80hp timing issues

S

slorole

Member
Hello every one
I have acquired a 1978 mercury 800 80hp that has been setting for about 15 years.
Electrolysis had set in and destroyed most of the wiring so first things first I checked
The compression and its running 130 to 135 all four cylinders, so I began the task of
Replacing the electrical.
Replaced the stator, the trigger and the whole wiring harness, thoroughly cleaned the carb's

Replacing all gaskets, replaced all fuel lines.
Done the Timing Point Adjustment
But when doing the Primary Pickup Synchronizing Timing it look as throw the cam never touches
The carb pin all the way throughout the first cam cycle.
I can get the engine to run but only till it’s put in gear and it stall’s and dies.
I believe it has to do with the timing but that’s back to the cam issues .
Can the cam be wore that bad are am I missing something.
Bi the way, I’m doing this from the seloc manual.
 
First of all that cam does not always have to touch and you had best not move anything on the timing untill you are 110% sure that needs to be adjusted !!----------------Timing on an outboard is fixed and normally does not need adjusting !!!--------------So look for the real issue here and it may be time to revisit carburetor cleaning.------They have to be taken apart for cleaning !!
 
They have to be taken apart for cleaning at local shop but I'm taking them apart again now to clean and check float adjustment's.
 
well after 3 hr of cleaning, setting the float's. it still has the same issues.
I'm starting to think its set up so long that the reeds cant handle it.
 
I don't think it is the reeds , unless one is held open by debris.------------They are quite reliable and operate with changing pressures.----------Try adjusting the low speed jets ----------------If it is idling and stumbles then open them both up 1/8 th turn and try again.---------Do you have spark that will jump a gap of 3/8" on all 4 cylinders ??
 
had to go check but yes it has a good blue arc 3/8" on all 4. after setting the jets 1 1/2 from lightly seated. put it in gear and it dies. backed off 1/8 turn
multiple attempts till the point there's no tension on the jet spring still dies.
 
You have good compression !---------Good spark !!!!!----------------My bet is a fuel issue.-----------Blockage in the carburetors.
 
Might just be a hard varnish blockage in the engine's fuel line connector since the carbs have been done twice.
 
Do you by any chance know why it sat unused for 15 years ??----------------Any chance mice or other critters got in the motor somehow ???--------You also MUST install a new waterpump impeller if it sat that long !!
 
as of this year the man I got it from is 96 years old, it is mounted on a 1978 15' venture 1550. last time he was going to use it was to take his grand son fishing. but that trip never happened. his grand son ended up in jail and the boat was put in the barn and never used again.
it was covered with dirtdobber nest, but nothing could get internal.
I know I didn't say so but the water pump was 2nd thing changed.
 
well I rebuilt the fuel pump and still the same old issues.
I went and had a talk to the guy I got the boat from, he stated that he never had any thing replaced on the motor and he bought it new.
so I guess I'm starting from the step one again.
 
Did you move anything on the timing?If you did,did you set it with the engine running in water and in gear?
Still sounds like a fuel issue.When setting the idle did you have it under load? If you want to check the reeds,pull the carbs,you'll see the petals,very gently push each petal to be sure they aren't sticking.
Crankcase seal, top or bottom or both?
 
at this point I got it going into gear and not dieing at about 1100 rpm but I need it under 1000 but any thing under 1100 stalls and dies. that's why I believe
the reeds are weak or sticking.
and yes sir. it's in gear under load in a tank.
 
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Sorry but I had to ask,clutching at straws.:).It's rare for the reeds to go and means splitting the case to inspect.Are the restrictors in place? Worth a look before splitting the crankcase
 
...has been setting for about 15 years. Replacing all gaskets, replaced all fuel lines.
Click to expand...
How about the connector on the engine?

I still think the fuel connector is plugged. Fuel varnish can get hard as dried paint. Somebody had the same issue and tried changing everything last summer on a boat that sat a few years and a boat shop found the connector on the engine plugged. I sure as hell would rather clean a connector before I crack open a case.
 
don't [FONT=&quot]Apologize!! I've had a lot of help from you, and could have missed something and your [/FONT]clutching at straws could be the answer.
 
guyjg said:
How about the connector on the engine?

I still think the fuel connector is plugged. Fuel varnish can get hard as dried paint. Somebody had the same issue and tried changing everything last summer on a boat that sat a few years and a boat shop found the connector on the engine plugged. I sure as hell would rather clean a connector before I crack open a case.
Click to expand...
I have made an attempt at cleaning the connectors on both carb's including the fuel line "T" every thing seems to be clear.
 
I'm talking about the main fuel female receptacle on the engine that the external fuel tank line w/squeeze bulb attaches w/male probe connector.
 
(good morning) guyjg I broke down the receptacles on the engine and the tank line clean them, only thing that looked bad was an O-ring on the
engine side so I replaced it, put it back in water tank but it didn't change any thing. but it was worth a shot.
 
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...I believe the reeds are weak or sticking.
Click to expand...
If they are sticking a good spray Seafoam cleaning with engine running may do the trick. Keep the RPMs up to 1500 and spray it into the carbs alternating 10 second sprays in each for a minute or two. Shut it off and let it soak for 30 minutes. Repeat several times. It will smoke alot but won't harm it one bit. It will clean out all the varnish and carbon from the engine. It just may do the trick.
 
What I would do here is remove the plug wires one at a time (carefully) with the motor idling to see what cylinders are not hitting. Use a plastic pliers and try not to shocked to death.
Timing issues will this problem. The pickup timing needs to be exactly right. You are doing this with the timing gun, right?.

One other thing that will cause problems is the bleed restrictors in the intake ports. They are plastc orfices and thay fall out. This is inside the transfer port side cover. Not the exhaust plate.
 
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timebandit said:
What I would do here is remove the plug wires one at a time (carefully) with the motor idling to see what cylinders are not hitting. Use a plastic pliers and try not to shocked to death.
Timing issues will this problem. The pickup timing needs to be exactly right. You are doing this with the timing gun, right?.
Click to expand...
Im getting plenty fire over 3/8" on spark tester have new plugs (could be one is week) Ill change them again. I am using a timing light.

One other thing that will cause problems is the bleed restrictors in the intake ports. They are plastc orfices and thay fall out. This is inside the transfer port side cover. Not the exhaust plate.
Click to expand...
I'll have to look over the book to see what it takes to check this out.
 
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slorole said:
Im getting plenty fire over 3/8" on spark tester have new plugs (could be one is week) Ill change them again. I am using a timing light.

I'll have to look over the book to see what it takes to check this out.
Click to expand...

I am trying to isolate any powerhead problems with air leaks or worn out cylinders.
 
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