Motor problem

[Jigger]

Hey guys, was out at Scugog last night looking for some 'skis. Seems the skunk bug is catching, I didn't even get a follow. Thats the report. At one point I fired up the big motor and had no problem getting on plane and cruised a good distance to the next spot. No problem. Dropped the trolling motor and fished for awhile and decided to call it a night. Fired up the motor again and got on plane and then, out of nowhere, the motor bogged out! what the heck! Its never done that before. So I started it up again and the idle speed was at least twice maybe even three times as fast as it should be...so I took the cover off and played with the throttle a little and had to manually push the little arm that controls the carb back to normal idle speed(Sorry, my mechanical terms are less than technical). Once again got going, but the motor kept wanting to crap out and I had to give it a little choke(Wanted to give it a BIG choke) to keep it going. Once it got on plane, which took what seemed like an eternity, top speed was less than half! I'm not sure at all how to proceed with this, is this something I can fix with a little tutorial, or should I send it in? The motor is a 1997 30hp Mariner. Its been a very reliable motor until this point and I'd like to get it back up to par as quick as possible. Any help would be greatly appreciated, thanks.

[Billy Bob]

Since you mention that you had to choke the engine to keep it running that tells me you have a fuel flow problem. Check all hoses, vents and priming bulbs for any leaks or defects. It also could be your fuel pump. It definitely doesn't sound like it's a ignition problem.

 

Bob

[misfish]

Have the needle valve checked in the carb. Maybe sticking.Do to too much oil.

[Sinker]

Could be as simple as your fuel line from the tank.

 

Certainly sounds like lack of fuel....

[Greencoachdog]

When was the last time you changed your fuel filter?

 

Like mentioned before check your fuel lines for cracks. When was the last time you replaced them? My maintainence schedule to change them every 3 yrs.

 

If you change your fuel filter and lines and it's still running crappy, take it to a marine mechanic to have it checked out.. prolly trash or build up in your carb(s).

[POLLIWOGG]

Buddies motor did the same thing, bog down - choke and away it goes. I cleaned the carbs for him and it worked fine for a while and did it again so he took the carbs apart and found a dandelion seed in the main jet. Gas has to be in the carb for it to pick it up by choking it so its not likely a filter or line or it would just run out of gas. Check the main jets. I would think it speeds up at idle because its running lean with something in the jets.

[taper]

Are your main motor and kicker both on the same fuel line. If so it is possible to cause a vapor lock in one motor while running the other, when you switch the motor will be starved for fuel. Normally it would run for a while and then shut down completely not run at half throttle. Just throwing out ideas.

[Jigger]

Thanks alot for your ideas! I borrowed my friends earmuffs and have some time to get it done this weekend. If ever there was a weekend this year that this had to fall on, I guess it would be this weekend. Tonight have my daughters recital to attend, tomorrow is her B-Day party and then Sunday is her birthday. I think I can sneak in enough time to muck around with the motor. If all external checks (change fuel filter/damaged hoses) don't work, I'll have time to take it somewhere tommorrow morning.

 

One question. Can the carburator be taken off without damaging/altering anything? Just so I can take a look at it. ?And maybe clean it?

 

You've all got me very interested in the mechanics of the boat all of a sudden! Thanks again for sharing your knowledge!

 

Oh and taper, sorry if I confused you, theres no kicker motor, just the 30hp.

 

One more quick one, is there any way to purge the lines without getting gas everywhere? Or, should I just disconnect the fuel line and run it until it is dry? Did I just answer my own question? Disregard the last question if I did...

Edited June 15, 2007 by Jigger

[Billy Bob]

You could save yourself some time and work if you get some Sea Foam and put some in the gas tank and run it though the carb. If it sounds like it's getting better you know you have a dirty carb and cleaning may be in order if the Sea Foam doesn't clean it out completely. Another thing is change spark plugs.

 

I know if I run my Johnson (50hp) in the driveway with the ear muffs it runs like CRAP because it doesn't have any back pressure on the exhaust. Put it in water and it purrs like a kitten. I don't know if the Mariner will be the same but I thought I might just warn you about that.

 

One more thing. Did you put a gas stabilizer in the gas and RUN it though the motor before putting it away for the winter. This is the NUMBER ONE cause to gunk-ed up carbs. This is a MUST before storing any motor, especially a outboard. I have been doing this for over 25 years and knock on wood no carb problems ever.

[bigbuck]

I'd second the old gas. Try to run the tank dry then put in some fresh fuel along with some sea-foam. That might fix the problem, otherwise, start looking from the tank to the carb for any obvious problems. If it comes down to messing with the carb, get a marine mechanic to look at it or at least a buddy who is REALLY good at this sort of thing.

Good luck.

[Tacklebuster]

it could be old gas, could it perhaps also be the choke mechanism isn't working properly?

[Jigger]

Not a choke problem, the choke was the only thing that kept the motor going at times. All indications seem to be pointing at old fuel. I hate to admit it, but I didn't put any stabilizer in the fuel last year . So, I guess its the lines and carb that are at fault.

 

There are two bolts that hold the carb on. If I take those off, will the carb stay in one piece? I'm not going to take it apart, I was thinking that I could find some marine carburator cleaner and dunk the carb right in for awhile. If I can do this myself without damaging the carb, I'm all for saving a buck!

 

IF I can pull the carb off, will the gasket need replacing?and how will I know if its all right or in need of a cleaning?

 

Thanks again.

[pikehunter]

One more thing. Did you put a gas stabilizer in the gas and RUN it though the motor before putting it away for the winter. This is the NUMBER ONE cause to gunk-ed up carbs. This is a MUST before storing any motor, especially a outboard. I have been doing this for over 25 years and knock on wood no carb problems ever.

 

I was thinking the same. I had a problem twice with my 2005, 25hp Johnson. Older gas, even though it was bought in the same season it had sat around for a month or so. The motor ran OK for a while but started to crap out on me as I neared the last in the tank. Had to run it at a higher throttle or pull out the gas knob to keep it running, sounds like the same symptoms as you have. A fill up of new gas and it ran like a dream once again.

 

Now I use Johnson's own brand of stabilizer/conditioner in the gas. Not only to keep the gas fresher but to help the motor burn the new gas with the added alcohol in it that they are all now selling.

[Zamboni]

Not a choke problem, the choke was the only thing that kept the motor going at times. All indications seem to be pointing at old fuel. I hate to admit it, but I didn't put any stabilizer in the fuel last year . So, I guess its the lines and carb that are at fault.

 

There are two bolts that hold the carb on. If I take those off, will the carb stay in one piece? I'm not going to take it apart, I was thinking that I could find some marine carburator cleaner and dunk the carb right in for awhile. If I can do this myself without damaging the carb, I'm all for saving a buck!

 

IF I can pull the carb off, will the gasket need replacing?and how will I know if its all right or in need of a cleaning?

 

Thanks again.

 

Leave the carb on, fill your tank with new gas/oil and Seafoam(NAPA stores carry)....spray little carb cleaner in. Probably have varnish that remains when gas evaporates in jets or needle valve....it should dislodge with seafoam/carb cleaner.

[boatman]

Not to be contradictory, but if the carb is gummed up enough to cause problems just running Seaform or spraying in carb cleaner won't fix it.

 

It does sound like fuel starvation. Clean or replace any fuel filters, pump fresh gas through the lines and then clean the carb. You will have to remove it from the engine and completely dismantle it. If you don't take it completely apart and clean out every nook and cranny it will probably plug again. What has likely happened is that some gunk in the carb lifted and partially plugged the float needle. Soaking in carb cleaner will only serve to destroy your seals and to loosen any and all gunk in the carb, which could make a bigger mess when you try to run it. I expect a marina would charge about $100 to rebuild your carb (one hour labour + parts and taxes). If you are not comfortable doing it yourself then take it in. Never hurts to have a professional look at it.

[POLLIWOGG]

If it was the float valve not seating it would flood the motor not starve it, if the float valve was plugged choking the motor wouldn't draw extra fuel past it , Choking the motor makes it run better so there has to be fuel in the bowl for that to work so we can rule out the float valve and everything the other side of it.

 

You didn't say it was old gas so that means crud or water. Some carbs have a drain at the bottom of the bowl, you might get real lucky and get rid of it simply draining the bowl. If you have to take the bowl off to drain it you may as well pull the main jet and stick a needle through it, sometimes you can see through it and it will still be filmed over. If you have the room you might be able to do it with the carb on the motor.

[boatman]

"If it was the float valve not seating it would flood the motor not starve it, if the float valve was plugged choking the motor wouldn't draw extra fuel past it..."

 

Your assuming the needle is stuck open I'm assuming its partially blocked. If it was just the idle and intermediate circuit it wouldn't effect top end performance. Also, choking doesn't draw extra fuel in it limits the amount of air coming in, which makes for a richer fuel to air mixture. Priming draws in extra fuel.

 

Either way, there is either a restriction of fuel coming into the carb or in both the high and low circuits or in the low idle circuit and the atmospheric hole in the bowl. Top end is influenced at the high speed jet, the float needle or the atmospheric hole. If there is any blockage in any of these you will not get top end.

Edited June 16, 2007 by boatman

[camillj]

I say dirty carb (bad gas) ... or fouled plug... sometimes you'll be running on only one cylinder without even realizing it.... this will definitely show up at the top end ....

[POLLIWOGG]

I thought about the float valve being partially blocked and making low fuel level in the bowl low but wouldn't it just run out of gas at a higher rpm if it can't supply enough fuel to idle.

 

By closing of the air with the choke you lower the air pressure in the barrel creating more vacuum or a greater difference in air pressure across the carb circuits drawing in more fuel and making the richer fuel to air mixture.

 

I imagine he's going to find a lot of scuzzy stuff floating around in there.

[boatman]

Its not reaching high RPM's that why he's only getting half throttle. Probably just enough fuel working its way through to keep from dying at speed. I suspect you are right, though, there is likely some crap in there.

 

Also, we got so swept up with the carb...better check that fuel pump too.

[Jigger]

Well, I talked to a repair shop and the mechanic isn't in today. The guy I talked to said I could drop it off anyways. Looks like I'll be back in business soon enough. I'd love to do the work myself, but the old girl could probably use a tune-up anyways and if its not too expensive, I'd like to get a Hydraulic tilt and trim installed. Will let you know how it turns out. Thanks again guys!

[boatman]

That's a wise decision. Good luck.

[Jigger]

Alright, just got the old girl back. Guy dissassembled and cleaned the carb, changed the fuel filter and greased the nipples . Cost $80. Not too bad, considering it was last minute. He took me back to the shop to have a look at the fuel, it looked like there was water floating around in it and the oil and gas had totally separated . Not just a little ,either. Almost half of what was in there was floating. Did a moisture test that came back negative, so its not water. The verdict, bad gas . Alcohol in the gas. He didn't run the motor on my fuel, said he didn't want to take a chance and used his instead. Fired up and stayed fired up without a hitch.

 

Up until this year I've been running premium gas in there and don't think that I'll be using the regular grade gas anytime soon. His recommendation was to use mid-grade, but since I had no problem with the premium, I'll stick with that.

 

Thanks again for the help guys.

[boatman]

Use either 87 or 89 octane. The high test is not designed for your motor and will leave more deposits in the combustion chamber. Those deposits could negatively effect your motor in the future.

 

Phase separation of alcohol and gas is going to be a bigger concern in the future as we move to ethanol fuels. The best way to protect your motor is to always add fuel stabiliser to your fuel and never store fuel any longer than you have to.

 

Also, glad it worked out for you.

Edited June 20, 2007 by boatman

[Fisherman]

Use either 87 or 89 octane. The high test is not designed for your motor and will leave more deposits in the combustion chamber. Those deposits could negatively effect your motor in the future.

 

Phase separation of alcohol and gas is going to be a bigger concern in the future as we move to ethanol fuels. The best way to protect your motor is to always add fuel stabiliser to your fuel and never store fuel any longer than you have to.

 

Also, glad it worked out for you.

Right on the money...