Honda B75-starts, revs up, but dies when slowing to idle speed.

NatureDriven

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Sep 5, 2009
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Hi all,

New to the forum here, after reading many posts, it looks like there are some pretty knowledgeable folks on here, hopin' I can get some good advise.

I recently purchased a Honda B75 4-stroke that hasn't been started for at least a couple years. Prior to it sitting, the motor would start up, idle and run with no problems on the first or second pull. I'm not sure of the year, the motor reads "B75-1005709". When I brought the motor home I immediately drained and changed the oil with 4-stroke marine grade 10w-30 oil. Also checked the plugs, and they are good. I've been able to get her started and revved up to the max with the choke pulled out half way; however, after I let her run like this for a few minutes then slowly start to wind her down to idling speed she dies out. Also, it pee's a steady stream of water.

Anyone have any idea's of what could be causing this?
 
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Sea Rider

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Sep 20, 2008
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12,345
Re: Honda B75-starts, revs up, but dies when slowing to idle speed.

1-Why are you reving up to the max with the choke pulled out half way ?
Start your engine as the manual recommends, push choke back in when warm, asume you are testing your engine at home, if so, bad idea, place engine on boat and go for a prudent cruise ride changing speeds to let time for the engine to settle down & carburate correctly.

If at idle the engine dies, check your low speed adjustment screw (it it has one) probably is a bit low, turn CC in increments of 5? untill engine maintains constant ide speed. If still dies, check gas/air mixture screw, probably to lean.

Happy Boating
 

NatureDriven

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Re: Honda B75-starts, revs up, but dies when slowing to idle speed.

Hi Sea Rider,

I've got the motor in a giant bucket entirely submerged as it would be in the water. The only way to keep the motor running is by having it on full throttle and the choke pulled out half way. Pushing the choke back in or letting off the throttle kills it. I'll make sure to look into the screws you mentioned after work and see if that helps. One thing, I'm very very new at owning a motor like this, have any idea what I should look for when searching for the speed adjustment screw or the gas/air mixture screw

Also, anyone have any way of identifying the year of this engine via this number found on the side of the motor "B75-1005709"

Thank you.
 

Sea Rider

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Sep 20, 2008
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12,345
Re: Honda B75-starts, revs up, but dies when slowing to idle speed.

Better get a service manual and have a look, so not to play around guessing wich screw is which, adjust idle speed screw first, if still dying, seems a gas problem, maybe cranked pump diaphragm or obstructed gas pipe that needs to be choked in order to deliver gas to carb. If still dying after having all issues checked, have it sorted out by a qualified mechanic.

Happy Boating
 

rdp

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Sep 26, 2009
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Re: Honda B75-starts, revs up, but dies when slowing to idle speed.

It's your carbs dude, I've got the same prob and the motor had only set since March, if you don't have the ultra sonic cleaner find someone who does and knows his chit to clean them, Check Craigs list under services. The shop wanted 150 per carb unemployed mech is doing it for 50 bucks
 
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