84 90hp mercury inline 6

[johnnud87]

This thing is extremely hard to start cold in the water. If it’s on the muffs it pops right off. Once it start and warms up it pops off every time unless it sits and cools. Approximately 3-4 hrs then back to hard start. Please help!! Occasionally once it’s warmed up and running I can go wot for around 3-4 min it will suck the primer bulb flat and start to starve for fuel. I’ve replaced all fuel lines and have tried two different tanks with vents open. I have also tried 3 different new bulbs.

 

[jimmbo]

First thing is a compression test.

Describe fully the procedure you use for starting it cold.

A 1984 inline 6 engine does not use a choke, but has an Enrichment System that drains fuel from the upper carb into the induction system of the lower cylinder. Have you tried spraying a bit of mixed fuel into the carbs to see if it fires right up? DO NOT use Starting Fluid, that is a surefire way to wreck a gasoline 2 stroke.

You say the primer bulb goes flat no matter what. That means a restriction between it and the fuel pick up in the tank. How old are these tanks?

 

[racerone]

Are you raising the fast idle lever all the way for cold starting, yes or no -----Are you pushing the key in while cranking it over for cold starting , yes or no ?----A BRP / OMC electric primer set up conversion is one way to get instant starting when cold.-----Has the battery been load tested ?----Have you made sure that the starter can crank it over very fast ?----Agreed the bulb going flat means that there is a blockage.---Easy fix.

 

[johnnud87]

I have tried the idle lever in every position. Key is pushed in on cold starts. The battery has been load tested and is new this year. Starter spins great. As far as easy fix on the bulb going flat, I’ve have replaced everything from the tank, pick up tube and fuel lines, fuel filter. Absolutely no restriction from the tank to the motor. Even my local marina is confused as to why it’s being sucked flat. Obvious answer is yes a blockage but unfortunately in my case there isn’t. I have even tried bigger fuel line. This only happens every once in a while and only at wot condition.

 

[johnnud87]

Jimmbo, I was unaware that that is how the choke worked on this engine. Thank you for that info, it may be a silly question but how to I verify that is working correctly? And I have not done a compression test yet. Yes if I spray gas into the carbs it helps but it still has a hard time. As far as the bulb. The original tank is 20 years old. But with that being said I have tried my jon boat tanks witch are only a year old. All venting is working and no restrictions.

 

[johnnud87]

It starts absolutely perfect when out of the water on the muffs.

 

[jimmbo]

You say the engine is an 84, I will assume it has a control box like this

On this type. there is no separate Fast Lever. To utilize a Fast Idle control, You press the square shaped button located on the Lever's pivot point. That will disengage the Gear Shift and allow the throttle to be advanced in Neutral

Remove the fuel pick ups from the tanks and examine the Filter/Strainer on the end of the pick up tube. I used to find a Jelly-like mess on the pick ups in my tanks. Or you might have water in the tanks

I guess it is possible for the hoses that are part of the enrichment system to be clogged by gum from stale fuel. That would prevent the system from working.

I never had a bit of trouble starting my 84 115 when cold. Good thing, as it had a bad battery for a while and I had to rope start it. It almost always fired and ran on the second pull.

It will appear to start and run perfectly fine on just 3 cylinders on the muffs

 

[johnnud87]

Yes same controls. I have tried that, but I will definitely take them out and look again. Can you explain more about running on 3 cyl on the muffs? All 6 don’t fire on the muffs?

 

[jimmbo]

They are supposed to fire. I was just saying that the engine will appear to be running fine on the muffs even if 1/2 of the cylinders weren't firing. Once in the water where there is back pressure in the exhaust, it would be a different story

 

[racerone]

The motor should start nearly instantly if the enricher is working.----Time to check that item out.----Post results of a compression test.----Crankcase compression issues can lead to hard starting in the lake.-----Cylinder compression and crankcase compression are not the same thing.----And perhaps 2 or 3 of the 5 bleed inserts are missing.----They are found behind bypass covers.----I am sure you are now confused , but some inspection / trouble shooting needs to be done here.

 

[johnnud87]

Ok, thanks everyone for the help on starting issue. Took it out twice this weekend. I did pul lines off to check the enricher system it was working properly I was just miss informed on how the choke actually worked on this engine. I realized that I need to hold the key in for atleast 10-15 seconds before I crank to allow the fuel to actually get to the cylinder. As far as the ball sucking flat it did fine all weekend with no issues. Again thank you all for your help. I really appreciate it... happy boating!!