Mercury 115 thunderbolt will run good out of water but will not in water

[reaper42141]

This my frist post here and i'm looking to buy my first boat but have a ?. I'm looking at a 15ft 1972 babcock with the 115 mercury thunderbolt on it. The guy said when he bought the boat2 months ago he took it to the water put it in but when he gave it gas it just went at idle speed so he had the carbs rebuilt and the trim redone also. He took at back to the lake and put it in the samething happen so he took it back to the shop and they told him it the throttle cable was bad. He told me he took it home and park it went bought new boat. ok the day i went and look at the boat he hook a water hose up to the mercury and it ran fine and he put it in FW and REV and it the prop turn with no trouble and no sounds so could it be the throttle cable or something internal with the motor any help with be very greatfull

 

[cell]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

Check the compression before you buy it....also was it peeing when you seen it running?Engines just don't run good one min,and bad the next with out a reason.But generally if the compression is good,and it runs on muffs it should be a good one.It just might require some tlc to get it running perfect.Usually after a carb rebuild you have to take it out to the lake and adjust it also.Even if it runs good on muffs.

http://forums.iboats.com/showthread.php?t=168855

 

[Silvertip]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

A motor running on half its cylinders will sound quite good on muffs and will rev up very freely. But that's with absolutely no load on the engine. In the water the engine now has exhaust backpressure and shifting into forward now loads the engine so any internal issues will show up. If you don't know what an engine miss sounds like you should at least be able to tell that the engine is shaking quite violently as it struggles to gain revs. Do not buy this boat unless you understand what you are buying. The problem may be simple and inexpensive to fix, or it may be complex, labor intensive, and costly to fix. Never buy a boat or engine betting that it just a simple fix. If it was a simple fix the seller would have fixed it.

 

[reaper42141]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

Well this was the first boat i have seen the motor started out of water and it was shooting water out and it had a steaded stream shooting stright out. When the guy had the carbs rebuilt he had the compression check and it was ok i have the bill from the shop he took it too. The guy drop down to 400.00 so i went and ahead and bought it today. but after i got it home the cables are rusted and couple string are broken but it still move all the levers on the motor. his son said today that they ran the boat a few times and you could run it full idle speed but when you kick the throttle in nothing would happen.

 

[jc4thecross]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

Hey Reaper it may be something very simple, I bought a 73 merc 115hp I had it purring like a Rabid Cheatah but when i put it in the water it stalled continualy, A gentleman that knows the old mercs, told me if you have worked the carbs or ie. you must tune the engine in the water in gear under a load. tie down the boat to tralior an tune carbs and most of all have some one with you and be careful. My .02

James hope it helped some. ps my engine runs great like he said.

 

[cell]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

Just check the link I posted in my first post.It will run through the procedure.Also most important is to get a manual for your outboard.

I bought a 71 16' sidewinder with an 71 115 merc.Its an old boat+engine.I just went through everything.The controls..split the box,and grease it up.the fuel system...ended up trashing the fuel tank because of rust.Rebuilt the carbs,and did the link and sync.Run some seafoam through it.Change the lower end fluid.drop the lower end and change the impeller. I never been happier.She runs smooth now,and is the fastest boat I seen were I go boating(except for those 21' speed boats lol)The only thing I have left is replacing some wiring on the engine.

Just take your time,and do it right.

 

[allenprimo913]

Re: Mercury 115 thunderbolt will run good out of water but will not in water



hey cell?

how do you link and sycnh the carbs, can you share how you did it>?

step by step would be nice


tnks

 

[cell]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

I just used this forum for the instructions.click on the link.

http://forums.iboats.com/showthread.php?t=168855

this link has a lot if tech on it for your old merc.

http://www.maxrules.com/carbindex.html

But you should really get a manual....you can't find all the answers on line.least I couldn't.

 

[Plainsman]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

Go through this too:

http://forums.iboats.com/showthread.php?t=158086

 

[allenprimo913]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

i have another question, how would i use a timing light?

there is no markings on my flywheel but one line where it says MAX, that's it

no other mark, so i would not know where to set advance or retard settings.

what to adjust if i time it? which screw? no idea.

 

[reaper42141]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

Thanks for all the info I'm going to take it to the lake sunday and first see if i can tighting the cables up to the throttle then if that don't help i'm going to try to adjust the carbs see if any life come to the motor. i printed out the pages on the carbs adjustment and going to give it a try. and thanks again for all the help

 

[reaper42141]

Re: Mercury 115 thunderbolt will run good out of water but will not in water

LOL went to the lake today put the boat in the water pump it up. Went to fire it up. Boat turn over but nothing then i had my brother jump up front and told him to turn the key. Went to pump the hose and where the hose runs from the fuel tank into the motor it starts to pure gas at the motor every time i pump it all the gas shot out so i took a closer look. It's a plastic part that goes in and turn well it was half in and out so when i touch it all of it fell out a spring, metal ball, rubber o ring, then another plastic part fell out so know try to find a pic that show me how it goes back to togather. So maybe i can get it back in the lake tomorrow.