2 stroke boat motor acting up

[Finch]

I'll preface by saying the motor has never left me stranded - just left me sitting at a dried up fishing hole longer than I would have liked. Its a Mercury Mariner 40HP two stroke. It can sit for weeks and when I hook it up to water at the house, it'll start after a few tries. It cuts off a few times and finally starts and stays running. I feel like this is normal behavior. I let it run a few minutes and it cranks every time afterwards while at the house. When I get to the lake and unload, it starts usually on the 2nd or 3rd crank.

After riding for a bit to get to a spot, I turn it off to start trolling. I can be fishing for 30 mins to an hour and go to start it up again and it just will not start. What would make a motor not want to start after running smoothly for a while? I do run ethanol free gas in it and seafoam every other fillup.

 

[TSAMP]

Does it have a manual or auto choke? When you say it won't start, can you be more descriptive?

If an auto choke, there is a thermal coupler that can go bad. This can be tested with an ohm meter. Also there is a switch in some models for bypassing it, year of motor also would help.

 

[Eyeman]

It could be something as simple as your hose running from the gas tank to the motor.
Sometimes air will seep into an old hose and lose the prime.
Check the clamps and hose.
Has happened to me before.

 

[ScreamingPotato]

Sounds like after a lot of attempts it does finally start, yeah? Pumping that primer bulb do any good at all? If so, definitely suspect the pinhole/air in line theory, or back check valve in the primer bulb itself.

 

[svivian]

when was the last time you checked or replaced your spark plugs? if so what did your plugs look like? also when was the last time you cleaned your carbs and checked seals? Shouldn't take that much effort to cold start

 

[rclouse79]

I used to have to use a fogging spray to clean out the carburetor frequently. It was enough of a dirty pain that I would never buy a two stroke boat motor again.

 

[CorbLand]

If it runs fine once started and just wont start, I would start with checking the fuel line for a hole/crack.

How long does it take to get started after getting to your fishing spot?

 

[fulldraw1972]

The first thing I would check is the primer bulb. If it’s not hard the check valve in it could be acting up. But pump it till it’s hard and then just keep an eye on it.

I used to have a 60 hp Mariner (99 model).
My factory Mercury marine bulb went bad after 2 years. Put on an OMC primer bulb and never looked back.

 

[49ereric]

Worst case scenario crank seals leaking with a 2 stroke

 

[Seeknelk]

I just replaced the primer bulb again on my 84 115 Merc. It made all the difference, wouldn't even bark until we noticed the bulb just felt weird, check valve goes bad in them. Made re starts when fishing just a key turn when it was a pain everytime. Bulb was only 2 years old, they apparently suck now.

 

[Gutshot007]

Have a 93 25hp mariner . Has been bulletproof . Started running like crap then not at all . Changed plugs. Getting spark . Went to fuel system . Good gas. Gas from tank to motor and checked for cracked or leaking lines . Ended up pulling carb off for cleaning 12$ rebiuild kit . Runs great now . Did order "Quick silver " oem rebuild as well 90$ . Good luck

 

[cnelk]

Fuel filter

 

[Finch]

Does it have a manual or auto choke? When you say it won't start, can you be more descriptive?

If an auto choke, there is a thermal coupler that can go bad. This can be tested with an ohm meter. Also there is a switch in some models for bypassing it, year of motor also would help.

Understand that I'm new to boats as I just got this a few months back. It has a 94 Mercury Mariner. The choke activates when you push the key into the ignition. Once I've gotten to my fishing spot and fish a while, I go to start it back up and it just cranks but never starts. Then it'll start momentarily and shut off no matter if I raise up the idle lever. I just have to sit there and give it some time and it will eventually start and run good again after it starts.

It could be something as simple as your hose running from the gas tank to the motor.
Sometimes air will seep into an old hose and lose the prime.
Check the clamps and hose.
Has happened to me before.

I noticed ever hose connection is secured with a zip tie (even inside the motor once the cover is removed). Is this common? I was thinking the metal hose clamps would be better.

Sounds like after a lot of attempts it does finally start, yeah? Pumping that primer bulb do any good at all? If so, definitely suspect the pinhole/air in line theory, or back check valve in the primer bulb itself.

Correct. I know I've pumped the primer bulb before when trying to get it to start but don't recall it helping the situation.

when was the last time you checked or replaced your spark plugs? if so what did your plugs look like? also when was the last time you cleaned your carbs and checked seals? Shouldn't take that much effort to cold start

I haven't. I bought the boat used. They "look" new but this is something I can easily do. Added to the list. Haven't cleaned carbs or seals. That is a bit intimidating to me at this point.

If it runs fine once started and just wont start, I would start with checking the fuel line for a hole/crack.

How long does it take to get started after getting to your fishing spot?

After its ran smoothly and turned off, it can take 15 to 30 minutes to get started again. Then it runs fine. I do recall smelling gas while trying to start it. Flooded?

The first thing I would check is the primer bulb. If it’s not hard the check valve in it could be acting up. But pump it till it’s hard and then just keep an eye on it.

I used to have a 60 hp Mariner (99 model).
My factory Mercury marine bulb went bad after 2 years. Put on an OMC primer bulb and never looked back.

So should the primer bulb stay hard once pumped up? I just went and checked and it was squishy. I pumped it up and will check again. I'll add a new primer to the list.

I just replaced the primer bulb again on my 84 115 Merc. It made all the difference, wouldn't even bark until we noticed the bulb just felt weird, check valve goes bad in them. Made re starts when fishing just a key turn when it was a pain everytime. Bulb was only 2 years old, they apparently suck now.

Thanks. I'll go ahead and replace mine.

Have a 93 25hp mariner . Has been bulletproof . Started running like crap then not at all . Changed plugs. Getting spark . Went to fuel system . Good gas. Gas from tank to motor and checked for cracked or leaking lines . Ended up pulling carb off for cleaning 12$ rebiuild kit . Runs great now . Did order "Quick silver " oem rebuild as well 90$ . Good luck

Thanks. I'll do some research on cleaning the carb.

Fuel filter

My first thought. I pulled the motor cover and was hoping the fuel filter was a see through. It was not. Looked kind of hard to get to so I thought I'd attempt another day.

 

[Fatcamp]

when was the last time you checked or replaced your spark plugs? if so what did your plugs look like? also when was the last time you cleaned your carbs and checked seals? Shouldn't take that much effort to cold start

All of these things. If you haven't cleaned your carburetors I would suspect them.

First thing go buy or build a whole new fuel line just to take that out of the equation. Might as well replace the plugs at the same time.

What year is the motor?

 

[Finch]

All of these things. If you haven't cleaned your carburetors I would suspect them.

First thing go buy or build a whole new fuel line just to take that out of the equation. Might as well replace the plugs at the same time.

What year is the motor?

It's a 94. Any specific type of fuel line I should buy?

 

[Fatcamp]

It's a 94. Any specific type of fuel line I should buy?

You can buy fittings at Walmart and then go to your auto parts store and buy auto gas line.

Or Walmart might have a complete fuel line, but the cool kids say you should build.

 

[Fatcamp]

Is it two or three cylinder?

 

[Fatcamp]

I don't have a 94 manual, this is from the 2001-2014 manual.

 

[TSAMP]

I wouldn't go ripping into the carb yet. If it runs ok once started I'd exhaust some other mentioned items first. Lots of ideas here already shared.

 

[cjdewese]

I'd suspect the fuel pickup to the motor. The bulb should stay hard after youve pumped it.

How long was your longest run to or from a spot?