1985 Mercury 50 hp

[mtndew]

1985 Mercury 50 hp 2 stroke 3 cylinder. Haven't run in 4 years. Long story. Pumped out old gas and put in new non-ethanol premium. New plugs. Bottle of Seafoam. Runs like a champ. Motor is on a Bass Tracker Pro 17 and will not get on plane. When it run 4 years ago it would literally fly across the water. Was told by a boat mechanic that it was the hub so I saved up and had a new hub put on. The guy at the prop shop said that there was nothing wrong with the hub, he did add a little cup to the prop. Took it to the lake and still will not get on plane. Was told by another mechanic that it was the coils and he said to run engine and pull the plug wires and listen to a change in the engine sound. Pulled cylinder 1 and no change, rebooted plug wire and pulled 2, no change, rebooted and pulled 3 big change. Started running rough but kept running. Pulled the coils and as far as I can tell they are good. DVM reading .2 and .932 respectfully on the posts and the tower and neg. post. I am saving up to take it to the shop but if it's something I can fix and save me some money (on disability) and time that would be great! So I guess I am looking for suggestions and thanks for the help.

 

[jimmbo]

I doubt it is, in fact, I know it is not an 85, the 50 Hp of that year was 4 cylinder. Serial # please

Well, no change when cylinders 1 and 2 lost their spark, would say they weren't firing, but when you yanked the 3 plug it still ran but rough, You trouble shooting needs some refining
First thing to do is a Compression Test
You need to see if the spark can jump a 3/8" gap
Are all three carbs delivering fuel?
When the engine was put into storage, what was done? Fuel Stabilizer(though expecting it to be of any use after 12 months is being extremely optimistic). Cleaning of carbs, fuel lines, fuel pump, strainers, and fuel tank, might be required

 

[mtndew]

Going by the title that it is an 85. Cylinders 1 and 2 have spark. I got a little shock when I pulled the boots but I don't know if it is strong enough. When I pulled the plugs there was what looked like a little bit of oil on 1 and 2, 3 was clean. I am trying to find someone with a compression tester I can borrow to check that. I don't know how to check the carbs. The boat wasn't technically put into storage 4 years ago. I couldn't do that at the time. Prior to then the things you mentioned in your last line had just recently been done and I did pump out the old gas that was still in the tank and put in new gas and a bottle of K100.

 

[mtndew]

I stand corrected, it is a 1996 according to the title. I was looking at the boat title. Sorry about that.

 

[jimmbo]

It does appear that you are running on 2 cylinders, loss of compression, loss of spark, or lack of fuel, can all create that situation. You just have to rule out which one(s) are the culprit(s)
If the carbs are dirty(gum and varnish) they will need to be removed and cleaned, Float setting checked, reinstalled. The the sync between the carbs and the timing advance will need to be verified.
As I said, the spark needs to be good enough to jump a 3/8" gap.

K100, never heard of it. I will assume it is a carb cleaner. Carb Cleaners can dislodge dirt/gum/varnish allowing it to clog up circuits it the carb, starving the engine of fuel.

 

[mtndew]

K100 is Seafoam on steroids when it comes to water in fuel. The fuel I put in was new non-ethanol premium. I added the K100 just to make sure lol
If it's the carbs then that is beyond me and I will have to wait until I can afford to take it to the shop.
I added a bottle of Seafoam to 1/2 tank of gas (approx. 6 gals) this past Saturday before taking it out to check things out.
If it a compresson issue how bad is that?

 

[jimmbo]

If the compression is low, it could be a number of things, Bad Head Gasket, scored Cylinder/Piston, Carbon causing Rings to stick.

Myself, I suspect gummed up carb(s), or failed Ignition.

A ruptured/leaky Diaphragm in the Fuel pump could cause richness in the cylinder(s) that are utilized by the Pump