My mate John, has a 1984ish Merc 115 on his cruiser, he has a problem with it
A mechanic thinks its his "poor starting technique",
Starts 1st or 2nd time, he goes for a 8 mile run to an island ( Coney Island ), then when he goes to return home, it takes about 20 turns of the key to get the engine started, when running the engine is fine at all speeds,
Its a 115 Merc 1984ish straight 6,
2 stroke with surface gap plugs, starting has been a problem since he got the boat last year, though once running it seems to run perfectly at all speeds.
Starting sequence, prime until bulb firm, push key to apply choke and throttle forward as it starts to catch. ( No choke and it def won't start though when it eventually starts loads of blue smoke ).
Sometimes this results in a first or 2nd time start other times you could almost risk running the battery down trying.
Starter motor just serviced at start of this season.
He has replaced both batteries since buying the boat and they are fully charged as of start of season and minimal use.
He also changed the priming bulb as it was pretty old & not remaining firm no matter how much you primed it.
THIS DID HELP IN THAT SUCCESSFLL STARTS ARE MORE RREQURNT BUT IT HAS NOT TOTALLY SOLVED THE PROBLEM.
He also noticed the fuel line from tank to bulb is a narrower diameter than from the bulb to engine & he is not sure if this is normal or a contributing problem and if so which does he change for best the narrower or wider diameter tube.
It was also suggested to him to reduce the oil mix, he currently adds 400ml to 20lts ( 50-1 mix ).He is reluctant to do this but would try it if it solved the starting problem.
Runs well at idiling and all other speeds, just so tempermental when starting. CAN ANYONE HELP PLEASE.
Merc 115 problem
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Tremlett 15
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Tremlett 15
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- Location: Bangor, Co Down, Northern Ireland
Re: Merc 115 problem
Another question from me, for the Merc buoys,
On what size of outboards should you use either 5/16" or 3/8" fuel lines
I just got a 5/16" fuel line for my Merc 500 50 hp, told this was the correct one, is this correct??
On what size of outboards should you use either 5/16" or 3/8" fuel lines
I just got a 5/16" fuel line for my Merc 500 50 hp, told this was the correct one, is this correct??
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Alacrity
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Re: Merc 115 problem
Firstly DO NOT CHANGE THE OIL MIX. Mercs must be run at 50:1 no less. You can run them on a richer oil mix (i.e. 40:1) but not weaker. If he does this he will have far bigger problems than poor starting, he will be into a very very expensive powerhead rebuild.
I have the same engine & have similar problems myself. I find I have to use the ‘choke’ (it isn’t – it’s a fuel enrichment device that dumps neat fuel into the crankcase) after it has been stopped for only a short while as they seem to cool down very quickly. Mine also has pickup issues when opening the throttle quickly after it has been idling for a while although this was much improved at Hayling after I richened the idle mix up by ¼ turn (out) on each carb.
The things on my list to do/check are carb rebuild & replace the crankshaft seals top & bottom. I have already fitted a new fuel pump diaphragm. I would suggest you friend starts afresh with his fuel line with all new hoses & clips.
I have the same engine & have similar problems myself. I find I have to use the ‘choke’ (it isn’t – it’s a fuel enrichment device that dumps neat fuel into the crankcase) after it has been stopped for only a short while as they seem to cool down very quickly. Mine also has pickup issues when opening the throttle quickly after it has been idling for a while although this was much improved at Hayling after I richened the idle mix up by ¼ turn (out) on each carb.
The things on my list to do/check are carb rebuild & replace the crankshaft seals top & bottom. I have already fitted a new fuel pump diaphragm. I would suggest you friend starts afresh with his fuel line with all new hoses & clips.
Mercs are like women, no 2 are exactly alike. That's what testing is about. In general it is safer to test motors and props than women!
Re: Merc 115 problem
Firstly thanks for the advice and to Tremlett for the initial posting.
The engine in question is mine so I signed up to watch the thread. Not sure what qualifies as a classic boat but as my model is 25yrs old and no longer available I can't be too far off.
I will certainly keep the oil mix as is and not reduce it. This always seemed a bit of a risky venture anyway.
I have tried a new starting method,
Prime the bulb, push in the key to ensure choke but this time once I turn the key I release it as soon as the engine starts to kick and use the throttle lever to get the final start. A good engine rev and all good to go. Last 3 starts from cold were 2 first time starts and 1 second time start. Hopefully this is not a fluke so I will keep you posted on this.
The new fuel lines and clips will be replaced either way as advised by Alacrity.
Any advice on size ? as previously mentioned there is a narrower fuel line tank to priming bulb than there is from bulb to engine.
Thanks again,
John.
The engine in question is mine so I signed up to watch the thread. Not sure what qualifies as a classic boat but as my model is 25yrs old and no longer available I can't be too far off.
I will certainly keep the oil mix as is and not reduce it. This always seemed a bit of a risky venture anyway.
I have tried a new starting method,
Prime the bulb, push in the key to ensure choke but this time once I turn the key I release it as soon as the engine starts to kick and use the throttle lever to get the final start. A good engine rev and all good to go. Last 3 starts from cold were 2 first time starts and 1 second time start. Hopefully this is not a fluke so I will keep you posted on this.
The new fuel lines and clips will be replaced either way as advised by Alacrity.
Any advice on size ? as previously mentioned there is a narrower fuel line tank to priming bulb than there is from bulb to engine.
Thanks again,
John.
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Tremlett 15
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Re: Merc 115 problem
bluefin wrote:Firstly thanks for the advice and to Tremlett for the initial posting.
The engine in question is mine so I signed up to watch the thread. Not sure what qualifies as a classic boat but as my model is 25yrs old and no longer available I can't be too far off.
I will certainly keep the oil mix as is and not reduce it. This always seemed a bit of a risky venture anyway.
I have tried a new starting method,
Prime the bulb, push in the key to ensure choke but this time once I turn the key I release it as soon as the engine starts to kick and use the throttle lever to get the final start. A good engine rev and all good to go. Last 3 starts from cold were 2 first time starts and 1 second time start. Hopefully this is not a fluke so I will keep you posted on this.
The new fuel lines and clips will be replaced either way as advised by Alacrity.
Any advice on size ? as previously mentioned there is a narrower fuel line tank to priming bulb than there is from bulb to engine.
Thanks again,
John.
John, update......... ( I think ) see below
viewtopic.php?f=7&t=683
Re: Merc 115 problem
The new starting sequence plus change of priming bulb seems to have resolved the issue.
I will still change the fuel line and go with the smaller size for now as the line from tank to bulb is almost 4ft and is the smaller size while the line from bulb to engine is only around 18"long and is the larger diameter. As fuel starvation has not been a problem and in fact too much choke was causing problems I think it is safe to assume the smaller diamer will be fine. As apart from new fuel line the only difference this will make is to change the shorter of the 2 lengths to a smaller diameter.
Hope this rationale makes some sense to you all.
Thanks again for the help.
John.
I will still change the fuel line and go with the smaller size for now as the line from tank to bulb is almost 4ft and is the smaller size while the line from bulb to engine is only around 18"long and is the larger diameter. As fuel starvation has not been a problem and in fact too much choke was causing problems I think it is safe to assume the smaller diamer will be fine. As apart from new fuel line the only difference this will make is to change the shorter of the 2 lengths to a smaller diameter.
Hope this rationale makes some sense to you all.
Thanks again for the help.
John.
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Tremlett 15
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- Joined: Fri Feb 06, 2009 1:24 pm
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- Location: Bangor, Co Down, Northern Ireland
Re: Merc 115 problem
Hi john, having a problem posting a reply, this is my 4th, go for a new 3/8" line with bulb to match, phone me & I will update U
st 6 can burn out on smaller, may not be correct term but guys in usa say go 3/8" , phone me anytime for update
st 6 can burn out on smaller, may not be correct term but guys in usa say go 3/8" , phone me anytime for update
Re: Merc 115 problem
For what it's worth...
For my racing Yahaha 70, developing about 90hp and burning 5 litres of fuel in a 10-minute race, a 5/16" fuel line that actually had a a 1/4" element at the tank connection was never a problem. My guess is that the Merc wouldn't need anywhere near this kind of flow rate, so hose bore isn't critical perhaps.
When I first started racing, I had lots of fuel related problems, and the effectiveness of the engine-mounted diaphragm pump was called into question. So I fitted an electronic pump, controlled by the ignition switch, in the boat between tank & motor, and discarded the priming bulb. I never had another fuel feed issue, period. The pump was a neat little plastic-bodied unit made by FAI Automotive, I think it was the smallest one they made and I believe they're still available. In fact, I had a spare pump, which I used to replace the SU on the Albatross...200% more reliable!
For my racing Yahaha 70, developing about 90hp and burning 5 litres of fuel in a 10-minute race, a 5/16" fuel line that actually had a a 1/4" element at the tank connection was never a problem. My guess is that the Merc wouldn't need anywhere near this kind of flow rate, so hose bore isn't critical perhaps.
When I first started racing, I had lots of fuel related problems, and the effectiveness of the engine-mounted diaphragm pump was called into question. So I fitted an electronic pump, controlled by the ignition switch, in the boat between tank & motor, and discarded the priming bulb. I never had another fuel feed issue, period. The pump was a neat little plastic-bodied unit made by FAI Automotive, I think it was the smallest one they made and I believe they're still available. In fact, I had a spare pump, which I used to replace the SU on the Albatross...200% more reliable!
Re: Merc 115 problem
My chysler outboard use to cut out when hot and let cool for few minutes it would start fine found out it had early type of electronic ingnition called CDI¬ capactor discharge¬ unit ,it is a transformer and 2 large capactors,
REPLAEC THE CAPPICTORS AND IT WORKS FINE NOW
REPLAEC THE CAPPICTORS AND IT WORKS FINE NOW