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Thread: Any experience with 4 stroke carbs?

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    Member c6 batmobile's Avatar
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    Default Any experience with 4 stroke carbs?

    Ive been having some issues with my carbs. Took the boat to the shop and had them cleaned, apparently they were very bad. The boat runs great now but the shop didn't inspire a lot of confidence and said a lot of times when 4 stroke carbs get dirty they need to be replaced entirely. I don't know a lot about boat motors but if they are any thing like cars/motorcycles a good cleaning and rebuild kit should take care of them for a long time.

    Anyone have a similar experience or can maybe give me a little more insight on the inner workings of a carb on a boat motor? Its on my yamaha 50.
    Makin fur fins and feathers fly.

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    Member Frostbitten's Avatar
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    Sounds like they were trying to sell you something you don't need. There's no need to buy new carbs just because they're dirty. Clean/re-build and you're good to go. The only reason to buy new carbs would be if you damaged the carb body somehow.

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    4-stroke outboard carbs are very touchy, hard to clean if they get varnished badly, and sometimes they have to be replaced (especially Hondas). The passageways are very tiny and many have calibrated orifices pressed in instead of adjustable or replaceable jets. Just shooting a carb solvent thru the holes normally does not work and soaking in carb cleaner may or may not work. The carburetors also have to be synchronized using vacuum guages or manometers to make sure each carb flows exactly the same so the motor will run correctly.
    in other words, they're an absolute b**** to tune without proper equipment, etc. i hate them

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    Member c6 batmobile's Avatar
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    I know they are extremely tough to tune. It has to be done with a vac gauge and mercury meter. My question I guess would be more geared toward should I trust the rebuild and cleaning that was done to them. They have already been cleaned by a reputable boat shop but it sounded like they weren't entirely sure it would be permanent fix, like later this year I could potentially have an issue.
    Makin fur fins and feathers fly.

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    Quote Originally Posted by c6 batmobile View Post
    I know they are extremely tough to tune. It has to be done with a vac gauge and mercury meter. My question I guess would be more geared toward should I trust the rebuild and cleaning that was done to them. They have already been cleaned by a reputable boat shop but it sounded like they weren't entirely sure it would be permanent fix, like later this year I could potentially have an issue.
    You said in your original post that the motor runs great now. If that is the case, I wouldn't worry too much unless it started acting up again. With carbs, you typically get fair warning (hard starts, rough idle, reduced power) before you are completely DIW. Did they just clean them, or did they rebuild them too?

    Also, if they were that bad to start, you might think about where you get your fuel from and how you store the boat for the winter.

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    Member c6 batmobile's Avatar
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    Quote Originally Posted by NRick View Post
    You said in your original post that the motor runs great now. If that is the case, I wouldn't worry too much unless it started acting up again. With carbs, you typically get fair warning (hard starts, rough idle, reduced power) before you are completely DIW. Did they just clean them, or did they rebuild them too?

    Also, if they were that bad to start, you might think about where you get your fuel from and how you store the boat for the winter.
    They were cleaned and rebuilt. I did get fair warning which was good because I was out in whittier when the rough idle started and knew it was time to head back. We made it back and the next day it didnt want to go.

    The previous owner did not have a fuel filter installed (it sure does now) and I think thats where the problem began. Ive only owned it for 2 years now and I treat the gas and store it properly, although I did have a water issue this year I don't think it will happen again.
    Makin fur fins and feathers fly.

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    Member Frostbitten's Avatar
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    Default Don't overthink it.

    Quote Originally Posted by c6 batmobile View Post
    They were cleaned and rebuilt. I did get fair warning which was good because I was out in whittier when the rough idle started and knew it was time to head back. We made it back and the next day it didnt want to go.

    The previous owner did not have a fuel filter installed (it sure does now) and I think thats where the problem began. Ive only owned it for 2 years now and I treat the gas and store it properly, although I did have a water issue this year I don't think it will happen again.
    Sounds like you are good to go!! I haven't been running saltwater boats all that long (about 10 years), but I have figured a few things out in that time:

    - Preventive maintenence isn't optional, it's mandatory
    - Reasonable preparation and planning makes for a more enjoyable trip. "Reasonable" is the key word here. (It's reasonable for me to carry tools, oil, spare prop, first aid kit etc...its unreasonable to carry a spare outdrive, defibrillator etc, etc).

    Thinking about and preparing for contingecies, be they mechanical, personal, medical, or whatever seems like a likely issue is no doubt important to more enjoyable time on the water. Overthinking issues and trying to prepare for absolutely anything and everything means I'll rarely, if ever, leave the dock. I'll admit that often, there is a real fine line between the two.

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    Member c6 batmobile's Avatar
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    Quote Originally Posted by Frostbitten View Post
    Sounds like you are good to go!! I haven't been running saltwater boats all that long (about 10 years), but I have figured a few things out in that time:

    - Preventive maintenence isn't optional, it's mandatory
    - Reasonable preparation and planning makes for a more enjoyable trip. "Reasonable" is the key word here. (It's reasonable for me to carry tools, oil, spare prop, first aid kit etc...its unreasonable to carry a spare outdrive, defibrillator etc, etc).

    Thinking about and preparing for contingecies, be they mechanical, personal, medical, or whatever seems like a likely issue is no doubt important to more enjoyable time on the water. Overthinking issues and trying to prepare for absolutely anything and everything means I'll rarely, if ever, leave the dock. I'll admit that often, there is a real fine line between the two.
    I hear ya. I have the same way of thinking. I carry a few spare things with me, prop, water pump impeller, fuel filter, tool kit etc and definitely dont want to over do it. When this problem developed though and the motor decided it wasn't going to start there was nothing else I could do but bust out the paddle. Luckily I wasn't in big water or moving water. Thats what I want to avoid. I guess Ill just roll with it and pay very close attention to how she idles and runs and if I notice her skipping a little I won't go far from the dock.
    Makin fur fins and feathers fly.

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    The only way to properly clean a carb is during a rebuild, if they were rebuilt, as you say the shop did, and all is well with the way it runs now, then you should harbor no concern. If there truly was an issue with the carbs then you would have had to buy new ones, rather than the shop being able to rebuild the originals.

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    Member Sobie2's Avatar
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    I have had great success with my Honda 90s (carb models) using the blue colored Stabil for marine and ethanol. I also had my jet skiff's Honda 90 professionally synced and Afterwards they said I needed a rebuild (come on people!). So I just decided to do the Seafoam trick and things are better without the carbs needing a rebuild.

    Finally this past winter my fourstroke 5hp tohatsu needed a carb rebuilding at $110/hr, so I went out on my own and bought a new one.

    Sobie2


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    Make sure you use stabilizer in your fuel tank @ each fill.
    I also run a cleaner (Mercury Quikleen) in my boat. I also use Seafoam fuel treatment once or twice a year to make sure my fuel system stays healthy.

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    Member c6 batmobile's Avatar
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    Quote Originally Posted by DRIFTER_016 View Post
    Make sure you use stabilizer in your fuel tank @ each fill.
    I also run a cleaner (Mercury Quikleen) in my boat. I also use Seafoam fuel treatment once or twice a year to make sure my fuel system stays healthy.
    I'll have to start doing that I guess. I usually don't start adding stabilizer until august.
    Makin fur fins and feathers fly.

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