mercury 115 hesitating

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Vision91

Petty Officer 3rd Class
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Apr 3, 2012
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i have the mercury 115 1150 thunderbolt and im not sure what yr exactly my guess is around 1976 but anyhow the issue im having is it runs fine when in idle and not in gear then once i put it in gear and give it some throttle it boggs down and almost dies on me. if i pump on the gas a few times the rpms go up and runs just fine..my ? is am i having an issue with it running way to rich or a timing/sync issue...any advice on this would help..i do have a book for mercury outboards but unfortantly is for 1990 to 1994 and only covers 135 up too 275hp so its only used as a base line
 
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Chris1956

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Mar 25, 2004
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27,158
Re: mercury 115 hesitating

Bogging down when trying to accelerate is a symptom of a too lean idle mixture. Did you adjust them? If not, and it used to work, the carbs may be dirty.
 
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Vision91

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Re: mercury 115 hesitating

i did clean the carbs a mth ago when i bought it cause the guy i bought it off didnt winterize it correctly but didnt mess with any screws for adjustments..also put new plugs in and a new fuel/water serpartor and cleaned the fuel pump as well..all 6 pistons have good compression around 120 average also put in new wiring harness inside the engine and other misc stuff. as i mentioned in the first post after pumping the gas it gets up a goes no problem and runs like a champ..
 
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Chris1956

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27,158
Re: mercury 115 hesitating

What do you mean by "pumping the gas"? Do you move the throttle handle, squeeze the primer bulb, hit the choke, or something else?

How did you clean the carbs w/o removing all the parts, including the idle mix screws? Did you set the carb floats? Replace gaskets?
 
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Vision91

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Re: mercury 115 hesitating

i dont have a throttle handle mine is a foot one and thats what i push on a couple times...i removed the floats and all the screws that werent for mixture theres only one for that and it does have new gaskets.. and no i didnt set the carb floats not sure how to exactly so im thinking that might be my main issue. i did manage to take it out to the lake and i didnt have the issue at first until it warmed up, after that it kept on doing the chugging thing
 
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carholme

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Sep 4, 2010
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Re: mercury 115 hesitating

Vision;

Do you have your engine s/n and I'll get you the condensed version of the service manual.

Gerry
 
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Vision91

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Re: mercury 115 hesitating

yes i do and thankyou in advance ive been looking for a while now and can only find the original wiring diagram for the engine but its 3494897
 
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carholme

Rear Admiral
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Sep 4, 2010
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Re: mercury 115 hesitating

S/n comes up as:

115 1150 6-cyl 3270480 3525440 1972 USA

From here:

http://www.marinshopen.se/Motorer/O...cury2taktR66cyl80150hp/tabid/489/Default.aspx

It is a model:

1115102 MERCURY 1972 115

Parts Listing:

http://www.crowleymarine.com/mercury-outboard/451.cfm

OEM Service Manual P/N: 90-68647

Here is one available on ebay at an excellent price:

http://www.ebay.com/itm/Mercury-OEM...anuals_Literature&vxp=mtr&hash=item231c4e1a89

In the interim. here is a link to the condensed version of the Clymer manual which will help you get started. Let the page ;oad for several seconds and download soonest to your computer as the link is short lived.

http://web.ebscohost.com/serrc/pdf?...d-8b8a-adcc17f613a4@sessionmgr12&vid=4&hid=21

See the carb float setting on page 306.

Gerry
 
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Vision91

Petty Officer 3rd Class
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Apr 3, 2012
Messages
88
Re: mercury 115 hesitating

thanks again this will help me so much with a lot of things...so ill check the float settings and redo the timing and sync while im at it..also today while out on the lake my trim motor gave out on me...took apart the motor and found out that both my brushes disenigrated so now i have to find new ones if its possible cause i noticed the wires where riveted on
 
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mr 88

Commander
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Nov 3, 2010
Messages
2,122
Re: mercury 115 hesitating

Look at the link carholme provided for carb rebuild. I think you may have missed some jets/ passages in your rebuild. When were the fuel pumps last rebuilt? I think the trim pumps motors are the same as mercruisers and think Johnnyrudes use the same if you do not want to fix it or take it to a electric motor rebuild shop.If you are using pump gas you may want to retard the timing a couple degrees as today's gas may kill that engine over time or add a addditive/race gas mix to up the octane and run it at rec timing. Family cruising boat or go fast and I like it pinned, may sway your thought process on that one.
 
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