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gofishingtom

Marine Man??

24 posts in this topic

Have a older 4 stroke yamaha starts fine warms up then when i go to put it in forward it chokes and dies..and even if i squeeze the bulb thinking its not getting enough gas..but its getting enough gas and the carb is clean and injectors are clean..Had it in to a older marine mechanic who doesnt work on 4 strokes but it has him miffed as to the problem as he says its getting enough gas but something is stopping it from gas when you put it in forward position..Hope this might be enough information for you and you might have an idea...He says the next thing to try is a carb kit for it..

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Have you tried letting the motor sit in nuetral for a couple of minutes befor heading off. Sometimes thats the ticket.

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Stalls out under load...

What year does "older" indicate?

What happens if you advance the throttle slightly before going into gear? Does it still stall?

I'm actually wondering about your lower unit...Resistance?

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Sounds like a dead cylinder. Pull the plugs and spark test each. Also check the tips of each plug. A clean tip could mean a blown head gasket or a plug that is not firing.

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I do think it is possible fuel pump (lack their of) and I do agree to pull plugs and check. If possible do fuel pressure test. Also replace plugs if you already have not done so. This is what I would do if it was a two stroke.

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Have you tried idling it up via the neutral throttle control (either via pushing the button in on the middle of the control lever (if flush mount) or via the lever along side the main control box lever)? If so, does it cut out then?

I'd also check for spark and the spark plugs.

Start there.. and let me know what you find.

marine_man

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spark plugs are new and its getting spark..also pressure check and cylinders are all 100%..idles fine and let it warm up and still when it is put in forward position it sputters and stalls..the carb was cleaned and injectors are working and fuel bowl has gas in it..the guy that is working on it is very exp. in 2 strokes and is miffed as to why it doesnt get any gas when you advance it to forward.squeezes the bulb to try to give it gas to keep it running but still bogs and stalls...he was checking into a carb kit for it to see how much it could run for this model..as year not sure what year it is but i figure it is one of the first model possibly yamaha made its white..i would say 1999 model possibly...thanks for help hope this info might help me help him where to check next..

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I don't know if this will help but have you checked the air intake? My 25 hp Johnson would idle fine but when I gave it some throttle would bog, cough and sputter. There was a hunk of foam from the inside of the cover that had gotten into the air intake. Something else to check.

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Have you tried idling it up via the neutral throttle control (either via pushing the button in on the middle of the control lever (if flush mount) or via the lever along side the main control box lever)? If so, does it cut out then?

marine_man

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yes the idling doesnt help once you put it in gear she sputters and bogs once it wants to go..like it is starving for gas..but it is getting gas..could it be fuel pump..or do you think looking into a carb kit is the way to go..

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How do you know it is getting gas?

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I had a Yamaha 40 that acted like that and it was a choke diaphragm issue.

My .02

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If compression and spark is good and fuel is being delivered then I would take the lower unit off remove the water pump and hand turn in forward gear. From the description of what you mechanic has done the lower unit could be trashed and locked up.

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I agree with euro

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lower unit is fine as that has been done..its having a lean miss fire..he has taken the screw off and can see that it is getting gas..he describes it as a lean miss backfire..air intake is not plugged as he can see through it.does not have a choke diaphram on it..So keep the ideas coming if anybody has any other ideas...

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I do not know all the in and outs, but it sounds like manual fuel pressue test of fuel pump to see if with specs. You should be able to do an in line test while running with rabbit ears on and see if it drops out of spec.. this would at least rule out pump if it is not it. Possibley elec. (possibley a micro switch if they have one) they cut spark at this time. Possibley bring in for second opion.

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Quote:

Have a older 4 stroke yamaha starts fine warms up then when i go to put it in forward it chokes and dies..and even if i squeeze the bulb thinking its not getting enough gas..but its getting enough gas and the carb is clean and injectors are clean.

Is it possible to have both injectors and a carb? Is this engine carburated or fuel injected?

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Quote:

yes the idling doesnt help


I'm sorry, but I still don't understand what you're saying here. If it's in neutral and you use the high speed idle feature (revving up the engine in neutral) does it exhibit the same symptoms?

marine_man

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Quote:

Is it possible to have both injectors and a carb? Is this engine carburated or fuel injected?


I'm pretty sure if this is a 1999 model it's got carburetors.

marine_man

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I've seen the same question asked 3 times now but no reply to it. Dose it stall out while in neutral with fast idle?

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Is this a tiller or console mode??? Northlander is having a similar problem but it stalls when going into neutral ,,,could it be a neutral switch adjustment/malfunction???

Randoid

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yes it stalls and sputters when you use the fast idle..it is carb no injectors...the guy looking at it says its a lean miss fire.. you can idle it just fine and high idle it but the minute you put it in forward it sputters and stalls..he is checking with some other mechanices and see if it might need a carb kit..will let you guys know what happens..

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A lean miss fire should not cut out eng., or maybe computer see this and shuts down. I do not know, I have not had a lean or miss fire issue before, that stalls. Possible fuel pump still or leaking intake gasket or carp gasket to intake gasket. It cuts out, how many variables could their be? If you shift it back in Neu. does it stay running?

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Thank you for answering my question.

Based on your information now I'd say it's a carb or fuel pump problem. You either have some junk in the carbs, or, your carbs might not be in synch any more, especially if you or the mechanic adjusted one and not the rest, etc.

In regard to the fuel pump - you should be able to verify if the pressure is in spec or not.

Presuming you haven't put a carb kit in it lately it might not be a bad idea, but when it's done you must pay attention to how many turns the jets are in when you remove them to clean them and install them the same number of turns.

If you're still exhibiting the same symptoms it's probably time for a trip to the dealer. Synching 2 carbs by ear isn't too hard, but 4 is another story.

marine_man

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