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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4724
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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Have a 115hp inline 6, 2 stroke, and black decals. Mid

Customer Question

Have a 115hp inline 6 , 2 stroke , brown and black decals . Mid 80's ? . Distributor less ignition . The engine has been rebuilt top to bottom all NOS and new parts . The engine starts , idels and revs up good . Problem is it does not like to idel in gear and makes no power .
Submitted: 1 year ago.
Category: Boat
Expert:  Jeff G. replied 1 year ago.

Does the engine have the idle stabilizer on it?

How many turns are the idle mixture screws turned out?

Start and run the engine for a few minutes and immediately pull the spark plugs. Are you getting any water on the spark plugs, tiny dropplets?

What ignition tests have been done?

Look on top of the float bowls is there a small brass air jet?

What is the idle timing set at?

What is the engine serial number?

Do you know which high speed jets are in the carbs?

Customer: replied 1 year ago.
No idel stabilizer , 1/14 approx on idel screws , engine is responding when adjusting them . 6 atdc and 20 btdc . There are small brass air jets . When you punch it in gear on the trailer it make a monetary kinda howl noise . Vacuum ? Then wants to stall . The person that built the engine is a current Merc master tech . He had to leave for vacation . Didn't have enough of a window to figure out problem before his departure . Thanks for the effort
Customer: replied 1 year ago.
No answer for serial # ***** know jet size . They where the factory installed jets for a engine sold in the north east of our nation .
Customer: replied 1 year ago.
I have pulled plugs several times . They are very clean , not getting any color on them . Did not take notice of water spots .
Customer: replied 1 year ago.
Ran engine this morning . Outside temp was 55 degrees . Engine ran approx 5 mins and pulled 2 plugs . Found light color brown . Substance looks milky , also took notice of a lot of oil in test tank . The engine has a low water pick up so I run it in a large farm tank .
Expert:  Jeff G. replied 1 year ago.

Remove the kets in the top of the float bowls.

Your motor didn't come with a low water pick up, but that wouldn't make a difference.

The milky substance sounds like you are getting water in the engine. This is a common problem. You will need to have the exhaust side plates replaced. When the engine was rebuilt did he install a new inner water jacket?

Try richening up the idle mixture to about 1 3/4 to 2 turns out from lightly seated.

Customer: replied 1 year ago.
I had the low water pick up installed at LowH2o out of AK . I bought the engine with a bad piston . I pulled the exhaust cover , the inside area was completely contaminated with water . Did not see any cracks or anything else looked hard . I did strait edge inner and other plates . The very inside plate has worpage . Is there something else that should be inspected too . I see there's a water problem there not convinced that It's the exhaust plates .
Expert:  Jeff G. replied 1 year ago.

OK, the inner plate will need to be replaced.

Here is are complete instructions to do it right so it won't happen again. You do have to examine the engine carefully for any cracks, although they are really uncommon.

Unless the techs at the shop are over 50 they probably have little experience with that engine.

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