Outboard Motor Help

I have a 2002 Johnson 150 that I’m having a little issue with. It is having a little trouble running at slow speeds and often has trouble starting after it Kills. It will start right away after landing the boat and will idle just fine. Its only after trying to slow it down that it has a issue. If I run it Hard and then show down it seems to be fine. It seems the worst if I start it after it been sitting for awhile and I then start it and try to move slowly for a distance. Its had the problem since I got it 2 years ago but seems to be worse lately. I’m going to start by replacing the Plugs tonight ( They are the same as were in there when I purchased it – Not sure how long they were in their prior to purchase ) I’d also like to try some fuel treatment in case it bad gas or clogged carbs. What brand / Type of fuel treatment would be the best to try ( Sea Foam, Stay Bil, Ect ) One thing that I’ve noticed is that the primer bulb does not stay real hard. It is possible I have a lead someplace in the fuel line although I never smell gas – I’m not sure how hard the bulb should stay. I took the cover off this morning to pull a plug to get the plug # and took a look for a inline fuel filter thinking it may be a good idea to replace that as well – I could not easily see one. Is it possible that there is not a fuel filter? or did I not look hard enough to find it. Any thought or suggestions you have are appreciated.

I have the same motor. I don’t have the issue you described but I can fill you in on what I’ve learned about the motor.

I had an issue where it would drop a cylinder at 3000 rpm. After replacing pretty much every ignition component I figured out it was warped float bowls. I replaced the float bowls and haven’t had the issue since. I smelled gas with this issue.

I have the issue of the primer bulb losing prime and I improved the issue by making sure that it is in the vertical position all the time. Especially when pumping it.
Link

My fuel filter is located next to the oil tank. It is a large fuel filter/water separator. If you don’t have one, get one installed.

I’m sure Sheldon will reply with more help for you.

sorry I am late,eighteen hour days will do that to a guy.
question,are you using ethanol fuels???
what oil are you using and yes,its relevant.

if it runs fine wide open but dies out when trying to slow down it sounds like to me you have a needle and seat leaking by and flooding it at low speeds,or the idle mix screws are a tad out of adjustment.

those things are notorious for having too lean of a pilot jet in them and it worsens with age,ethanol gas use and/or too many solvents.
before I go any further,post a pic of all of the spark plugs as they came out of the motor immediately after a high speed run please and we will go from there.

pm me and I will give you my phone number so I can walk you through a diagnostic check as that motor is a picky sob.

Engine tuner did a real nice job cleaning the carbon from my engine. Noticably smoother after. Has lubricants so it doesn’t burn up your cylinders while cleaning. Not exactly a carb cleaner but worth doing.

Worth doing on a windy day away from neighbors. Unless you don’t like em….

Forget the surface gap plugs, i seen some websites promote them. Saltwater big open water run guys can use em, us not so much. Probably 78s for that engine, gap correctly.

nhamm wrote:

Forget the surface gap plugs, i seen some websites promote them. Saltwater big open water run guys can use em, us not so much. Probably 78s for that engine, gap correctly.

Hmmm. Tell me more. My boat sees primarily long runs (20+ miles) across Superior. By primarily I mean probably 75% of the hours in one year doing exactly this.

Of course my engine has treated me extremely well. Now I am seeing some rough idling though.

Been awhile since I read those forums but it was even recommended at one point on brp website, they may have changed since then.

Personally a fan of if it ain’t broke don’t fix it. If it’s treated ya well leave er be imo.

Ill probably be switching back to the 77s, put 78s in it this year and thought it idled better last year.

Iowaboy1 wrote:

sorry I am late,eighteen hour days will do that to a guy.
question,are you using ethanol fuels???
what oil are you using and yes,its relevant.

if it runs fine wide open but dies out when trying to slow down it sounds like to me you have a needle and seat leaking by and flooding it at low speeds,or the idle mix screws are a tad out of adjustment.

those things are notorious for having too lean of a pilot jet in them and it worsens with age,ethanol gas use and/or too many solvents.
before I go any further,post a pic of all of the spark plugs as they came out of the motor immediately after a high speed run please and we will go from there.
pm me and I will give you my phone number so I can walk you through a diagnostic check as that motor is a picky sob.

Iowaboy – Thanks for the offer to help. Please check your PM for more Info.

Iowaboy1 wrote:

sorry I am late,eighteen hour days will do that to a guy.
question,are you using ethanol fuels???
what oil are you using and yes,its relevant.

if it runs fine wide open but dies out when trying to slow down it sounds like to me you have a needle and seat leaking by and flooding it at low speeds,or the idle mix screws are a tad out of adjustment.

those things are notorious for having too lean of a pilot jet in them and it worsens with age,ethanol gas use and/or too many solvents.
before I go any further,post a pic of all of the spark plugs as they came out of the motor immediately after a high speed run please and we will go from there.

pm me and I will give you my phone number so I can walk you through a diagnostic check as that motor is a picky sob.

To answer the fuel question I use the standard 87 Octane
For Oil I normally run the Johnson Brand Synthetic

fishthumper wrote:

To answer the fuel question I use the standard 87 Octane

I suspect this could be a problem. I run only non-oxy in mine. I’ll go out of my way to get it.