96 Yamaha 115Hp Pro-V Not Idling...

[abomb55076]

I have a 96 Yamaha 115hp Pro-V 4 cylinder outboard motor on my Bayliner. Overall the motor works great, I am able to start it on the second or third try with the electric start while choking it and when in gear, there are no issues getting up to speed, sounds great, and never cuts out. The issue is when I am sitting at the boat launch or a dock and I am letting the engine idle, it typically wont idle for more than a minute before suddenly cutting out. I can restart it without any issues but I cant get it to stay idling. I have run a bottle of seafoam through the engine last year and also put all new plugs in. I've also attached a video of this event happening (at the end of the video). Any ideas what my issue may be? Any help is greatly appreciated.

See video here: https://www.youtube.com/watch?v=G3fnBaj3cmI

[Jason2tpa]

Good video, great idea to post. I need to do the same next time I'm having engine issues for these pros to see/hear lol.

I've got the same engine, '98. Sounds like the rpms are within normal idle operating range (700 +/- 500). Are they? What first occurred to me hearing how it cuts out abruptly is a fuel issue...it's not getting it. What happens when you open up the throttle a little while in neutral? If you haven't yet, bring up the rpms to say 1000 and see if it cuts out. Check the primer bulb...is it full or collapsed when the motor cuts off? If it's collapsed you've probably got a failing fuel pump.

You mentioned using a bottle of Seafoam "last year", which brings me to conclusion you don't regularly use a fuel additive. So it could be your carbs. When the last time you cleaned?

Just a few of my thoughts. The more details you can provide these guys the better. Hang tight and I'm sure they'll chime in. And whatever Rodbolt says just take it with a grain of salt. He's the pros pro on here, but he's an Aussie--

[99yam40]

Rod was located In NC last I saw

[pstephens46]

This thread gonna blow like the damn lower unit one....

[abomb55076]

Thanks for your reply!

When I open up the throttle slightly, the motor seems to do much better and that is typically what I do to keep it running when I want it to "idle". The bulb does not collapse when the motor cuts out.

As for fuel additives, I don't tend to put anything in the fuel unless I am storing it for the winter. When winterizing the motor I put some fuel stabilizer in it and tried some fogging fluid last year as well. I have only had the boat for two seasons now and have experienced this issue since I purchased it so I don't know what the previous owners practice is.

I have not rebuilt or cleaned the carbs yet because I have never done a dual carb system like this before, only small single piston engines. I did however purchase the service manual and a carb kit to try and rebuild them. Just haven't gotten the kit yet.

Any chance the carbs could just be out of sync also?

[TownsendsFJR1300]

It sure seems to idle fine before it stalls. And its very abrupt, not the typical RPMs slowing down eventually dying...

It doesn't sound like the idle jets are clogged, (it idles too smooth). I would check the air screws on each carb (exterior adjustment) and make sure their in factory spec (someone could have dinked with them over time).

I'd pull the drain plugs from the float bowls (drain bolt for each side of the carb) and catch the fuel that comes out in a CLEAN container. Check for any crap, water, etc.

The sync and timing are also critical, so yes, checking adjusting per the manual wouldn't hurt.

Are you using ethanol fuel and if so, is it fresh? Ethanol can go bad in as quickly as a month and varnish up the carbs.

BTW, since you've cleaned small carbs, the Yamaha carbs operate/ get cleaned like any other, just pay attention. And, make sure EVERY JET gets pulled and you can see light thru them. There's some very small holes in them that will clog easily. If you don't see light thru them, IT DON'T COUNT..

I would also strongly suggest running Yamaha's "Ringfree" and regularly a fuel stabilizer. The RF will help keep the varnish to a minimum and does clean the top end.

[rodbolt17]

Rodbolt is no aussie .

your carbs may need cleaning.
it is actually simple.

[abomb55076]

I suppose the next step is to clean the carbs then. Once the kit comes I will dive into it. I believe I can borrow a mercury carb synchronizing tool from someone I know that uses it for motorcycles so that should be better than the old water bottle technique. Anything else I should watch out for when pulling them apart or reassembling them so I don't totally mess them up?

[99yam40]

there is no place to hook up that synchronize you speak of on your carbs.
follow the link and sync procedure in service manual any time you put the carbs back on, and adjust/set to specs

[TownsendsFJR1300]

+1 ^^^, the carbs don't sync with a vacuum gauge, strictly mechanical.

Throttle bodies, (FI), yes, most do use a sync tool...

[Jason2tpa]

Rodbolt is no aussie .

Whoops, haha sorry bud. Thought for certain some of your slang was aussie!

[abomb55076]

Oh, I was under the impression that had to be used any time you have dual carburetors. That sounds even better, I should be able to follow the instructions then.

[TownsendsFJR1300]

Oh, I was under the impression that had to be used any time you have dual carburetors. That sounds even better, I should be able to follow the instructions then.

The vacuum sync tool is almost always (I don't know of any that don't) on multi carbed or FI'ed motorcycle engines. There's no adjustment for timing, (that's set with the ECU).

I'm sure other multi carbed / FI'ed engines do as well (jet ski, snow mobile, etc)...

[ausnoelm]

Rodbolt is no aussie .

your carbs may need cleaning.
it is actually simple.

Wish you were, you could get a job in a second... Might be time for a paid "holiday" down under!

[zenoahphobic]

Rodbolt is no aussie .

your carbs may need cleaning.
it is actually simple.

Dual citizenship can come in handy.