Motor stalls when idling

I just bought my first boat a few weeks ago, a 14' Landau with a early 90's 2 stroke 9.9 Suzuki.

The compression is the same in both cylinders. The previous owner said the motor runs but that it might need some carb work. When I got it home I put the motor in a trash can of water and got it running without much of a problem. Last weekend I decided to take it out on the local chain of lakes to see if it had any issues.

What I noticed is that at first if it idled for too long it eventually stalled out. Then after about 30 minutes on the lake I noticed that the time span of idling got less and less before it stalled.

After that, I decided to take the boat back to the ramp. As I was cruising around in circles at a low speed (but not idling) waiting my turn to use the ramp the motor started smoking and then cut off. At that point I didn't bother cranking the motor back up and used the trolling motor to get in.

Does anyone know what could cause these issues? Is it the carburetor or something else?

I'm fairly handy, like learning new things and working on projects. Is there a list of troubleshooting things I can go through to properly diagnose the issue myself? Does it take any special tools to work on outboards? Do you think I should try fixing myself or just take it to the boat mechanic? The compression is the same in both cylinders at 40/40. The compression seems low, but I don't know if that is standard for smaller motors. I was able to find the manual for the motor online but it doesn't say what the compression should be.

Any advice would be very much appreciated.

40 psi does seem low. Did you check it before or after you ran it on the lake? Did you change out the water pump impeller before taking it out?? It's one of the most important things to do when you get a used motor. If it wasn't pumping properly, and the motor overheated, it could explain your low compression and stalling problems.

The lowest I've seen on some of the smaller and older rope start motors is around 60 psi, typically its around 90 or better. Much less than 60, and the motors usually have a hard time starting and running.

When checking, make sure you open the throttle wide. Also, don't read the measurement until you've had two or three pulls on the rope without the gauge increasing at all. Repeat for both cylinders. You want both to be about the same pressure (Within 10%).

I hope you've simply got a bad reading, or you're going to be needing a full tear down, replacing pistons and boring the cylinder.

Good luck!

Thanks for the reply kofkorn. That compression reading was after I took it on the lake. I'm pretty sure I didn't have the throttle wide open when I checked the compression, at least I hope I didn't. I'm going to check it again tomorrow per your suggestion. I'm really hoping its a bad reading and doesn't require a full tear down.

kofkorn's right 40 is mighty low compression. When you check it again pull that rope like ya stole it. If the comp gauge is suspect stick in in your mower and check that comp. If that is low the gauge might be faulty. best of luck

And make sure you have both plugs removed also when you're pulling that rope for the compression check.

kofkorn hit the nail on the head - #1 thing you should do when starting off with a used motor is check the impeller - pull it apart and physically hold the part and inspect it - not just run the motor and see if water comes out the tell. It can be dried out, cracking, hardened, missing parts etc and still function well enough to push water through the tell for a test but then fail within 15 minutes on the water. The part is very inexpensive, so usually you just replace it for the ~1hr worth of trouble you'll go through pulling it apart to inspect in the first place (why do it twice???)

Until you verify/refute the compression it's hard to say what your issue(s) is/are. If all is well with the compression you obviously have spark so the culprit is probably related to the fuel delivery somewhere. Crud in the carb, bad carb float, stuck shutoff needle, bad fuel line, primer bulb, fuel filter, water in the gas, the list goes on.

You're going to pull the plugs anyway for the comp test - can you post a pic of them?

Kofkorn, per your suggestion, I made sure that the throttle was wide open. I lt wasn't open previously. Once I adjusted the throttle I got a higher reading but not real high, 50/50.

Charger25, after pulling the heck on that rope and making sure both plugs were out per JMichael's suggestion, the compression still wasn't great so I followed your suggestion and checked the compression on my lawn mower. The reading on the mower was really low too. No matter how many times I cranked the mower or how hard I pulled I never got a reading over 30.

This leads me to believe that the gauge is inaccurate.

I really wish I had found this site with all this great advice before I put the boat on the water for the first time. Hopefully, there isn't any significant damage done to the motor.

Onthewater102 here is a picture of the plugs I pulled. When I first attempted to get the motor started it would t start and so I pulled the plugs, gently ran a wire brush over them, put them back in the motor and it cranked right up. I bought one new plug from the local boat store but they didn't have a second one in stock at the time and I'm waiting for it to come in. Here is a picture of the old plugs that I pulled out of the motor.

Hi 10man,

Can you get us a picture of the end of the spark plugs? When you remove a spark plug, it can help to tell you the condition of the motor:

Black and sooty or oily means that your motor is running rich. It will run for a while in this condition, but it will eventually load up the plugs and performance will deteriorate until it is no longer running.

Clean and shiny, this can mean that you've got a leaking head gasket or a hole in your water jacket. The water is turning to steam and cleaning your cylinder. This is a bad condition that needs to be corrected immediately

White/light gray and powdery - Your cylinder is running lean - again needs to be corrected immediately before you burn a hole in your piston or toast your rings

Toasted Marshmallow or brown - Running with the proper fuel mixture, doesn't mean everything's perfect, but you've got a good mixture.

Definitely look into a new compression gauge. You want to get the true readings before doing any other significant work.

Good Luck!

Used motor - step one, replace the impeller.

Even though we can't see the end of the plugs they don't look to be that bad that they'd be causing you an issue. With them removed from the engine take a plastic handled screwdriver and put the end into each of the plug boots one by one and hold the screwdriver ~1/8" away from the metal casing of the power head and give the motor a pull like you would to start it. You'll have no compression resistance, so it'll spin pretty freely, watch while it's spinning to see if you have a good blue spark jumping from the screw driver to the engine. Test both plug wires to be sure, but that should rule out your ignition side of the equation pretty quickly (I really don't think it's the issue at all, but as easy as it is to test and know it's not why not test?)

Assuming spark checks out OK your problem is likely fuel.

Are you using a new gas tank or the one the previous owner had?
any chance of water in the gas?
possible bad check valve in the bulb (not likely, but not uncommon)

My guess is if it's not idling nicely your carb is the issue. Either clogged with gunk, or one of the rubber components inside did not play nicely with the ethanol in the fuel, or your float has a pinhole in it and is full of fuel & thereby not floating (this was my issue, and it followed the progression you described)

Kofkorn, I got a chance to take closer pictures of the spark plugs. By looking at them it appears that these fall into the category of black and sooty, and that its running rich. However, take a look at the attached pictures and let me know what you think. I had no idea that how engine is running or the problems it has can be diagnosed by looking at the spark plugs.

Onthewater, I didn't read your post about using the screwdriver to do the ignition test until after came in from pulling the plugs again. But I'll test it probably tomorrow.

The tank came with the boat and was the previous owners. The tank was half full when I bought the boat and I didn't drain the fuel, so I guess there's a chance of there being water in the fuel tank. Is it common practice to drain the fuel when buying a used boat?

How would I know or be able to check if there's a hole in the float?

If it is a carb issue I'm assuming that the carburetor would probably need to be cleaned or rebuilt? I've read on this forum of people talking about a "carb kit" or "carb re-build". Are those the same things for the most part or are they completely separate thing? What exactly are they? Is it just disassembling some of the components, cleaning some of the gunk out, and replacing the gaskets? If that is what it entails, does that usually solve the carb problems? Is a carb kit or re-build fairly simple to do, or do most people who do this know what they are doing? Is it something that most people can do their own and can tackle by following some YouTube videos or is it better to have a boat mechanic do it.

Lastly, where do most people buy parts for outboards? I'm assuming a carb kit is specific to the outboard, but what about an impellar? Are these specific to the particular outboard or are they pretty standard and just about any boat or marine store will have them in stock?

Sorry if these questions are off base or I'm getting ahead of myself. I'm just trying to learn about all of these things so that I am no longer an ignorant boat owner and can become better versed in the mechanics and know what to do/not to do now and in the future.

I really appreciate all the knowledge and help everyone has provided.

The10Man said:

Kofkorn, I got a chance to take closer pictures of the spark plugs. By looking at them it appears that these fall into the category of black and sooty, and that its running rich. However, take a look at the attached pictures and let me know what you think. I had no idea that how engine is running or the problems it has can be diagnosed by looking at the spark plugs.

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P.S. I realized after I originally submitted this post that I forgot to attach the photos. I edited the post and attached them but I'm not sure if they shoe up correctly. Let me know if you can't see the pictures of the plugs and I crest a new post.

First off, I was throwing a shotgun list of fuel issue possibilities at you, more so for future reference.

The10Man said:

The tank came with the boat and was the previous owners. The tank was half full when I bought the boat and I didn't drain the fuel, so I guess there's a chance of there being water in the fuel tank. Is it common practice to drain the fuel when buying a used boat?

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Common, for paranoid people like me yes, others probably no, but if you're having issues this is an easy one to rule out. Pour the fuel into your car's tank when it's close to full. It will dilute and run through the car without an issue and you can inspect the bottom for debris before filling it with fresh gas & oil mix...you did mix 2 stroke oil into the gas 50:1 right? Sorry - not to be insulting, just covering my bases...

The10Man said:

How would I know or be able to check if there's a hole in the float?

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You would inspect it when you have the carb pulled apart. You'll know it if you've got one, the float will be full of gasoline.

The10Man said:

If it is a carb issue I'm assuming that the carburetor would probably need to be cleaned or rebuilt? I've read on this forum of people talking about a "carb kit" or "carb re-build". Are those the same things for the most part or are they completely separate thing? What exactly are they? Is it just disassembling some of the components, cleaning some of the gunk out, and replacing the gaskets? If that is what it entails, does that usually solve the carb problems? Is a carb kit or re-build fairly simple to do, or do most people who do this know what they are doing?

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"Carb kit" is just as the name indicates, a kit full of all the parts you'll need to rebuild a carb. You replace a few more internal parts in a rebuild, but the idea is the same - clean the gunk out of all the tiny passages routed through the carb using a solvent cleaner (sometimes soaking it if it's really crudded up) and snaking them out using a material softer than aluminum so it won't scratch (monofiliment fishing line works great.)

You're asking all the right questions, so I think it's safe to assume your brain can put one foot in front of the other when you walk so rebuilding a carb shouldn't be an issue for you It isn't rocket science, but people get intimidated by it. Youtube will help you, especially if there are videos of your exact carb. The only part that you need to really pay close attention to is once you've got it all back together you will need to adjust the fuel mixture by either tightening or loosening the screw or screws in the carb. Each carb is different, but you usually start by gently tightening them until the bottom out, DO NOT FORCE THEM FURTHER, then you back them off a full turn or turn and a half (depending on the carb), start the engine in a bucket or on the earmuffs, and tweak the adjustment from there until you get the max RPM (which you judge audibly, no need to get nerdy and hook it up to any fancy test equipment.)

The10Man said:

Lastly, where do most people buy parts for outboards? I'm assuming a carb kit is specific to the outboard, but what about an impellar? Are these specific to the particular outboard or are they pretty standard and just about any boat or marine store will have them in stock?

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I order them online from www.boats.net - you enter your serial # and it will pull up the parts list with diagrams for your motor/carb etc. I doubt they'd be in stock anywhere, but a local parts supplier should be able to have them the next day if you wanted to go that route - but they're just ordering them online themselves...save yourself the profit to the middleman in the equation.

Guys - I didn't see anyone address the relatively low compression numbers. What's the take on this?

CMOS

CMOS said:

Guys - I didn't see anyone address the relatively low compression numbers. What's the take on this?

CMOS

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Agreed.... need to get or borrow another comp gauge and redo comp check and go from there

So I checked the compression with a different gauge and the motor still had low compression. After I got this reading I decided to take it in to the local boat mechanic and he confirmed that the motor had low compression and said there was knocking in the motor. He said its probably not worth spending the money to have them fix it. He stated that it needed a new impeller but that it wasn't guaranteed to fix the problem. He said after replacing the impeller the motor that it was hard to say for certain how much longer it would last and that could crap out tomorrow or it could last another year,

So, needless to say, I'm pretty disappointed. Im not sure what to do at this point.

Patience. There may be hope yet. This is a bit over my head but others will chime in with some ideas.

What exactly are the newly tested compression numbers?


CMOS

The compression numbers were the same as what they were previously. 50/50. The previous gauge wasn't incorrect after all.

Oddly enough in my local craigslist a guy is selling a similar motor in which the powerhead runs and the mid section is good but it doesn't have a lower unit. He even went to the trouble to post a video of the motor running on YouTube. He's only asking $50 for it. Here is the ad https://orlando.craigslist.org/boa/5108740890.html and here is the video https://youtu.be/PgpVJlNApig.

This motor might be a couple years older than my motor, but does anyone think I could possibly put my lower unit on this motor and be ok? Do you think I should reach out to the owner and ask what the serial number is to try to see if the upper unit and lower unit are compatible?

I could offer him $25 and not lose much, except for my time, trying to make it work.

What is everyone's thoughts? Thanks!

Get the s/n and go on boats.net, pull up both parts schematics and go part by part matching everything up. If the major components of the gearbox are the same you are probably ok to spend more time digging into the minutia.