78 Stinger75 starts and runs fine on land

[biggizmo]

Have been busting brain cells on this one.
1978 Johnson 75 Stinger starts up with flick of key on land with muffs and also in a tank. Runs great.
Put it in water...bogging death and sometimes won't start. Recently checked and cleaned out float bowls because of flooding. Not the problem.
New plugs...hot power pack...good battery...new fuel..
Seafoam treatment...etc.
In tank...removed gear linkage to test throttle power in forward and reverse positions...sounds and functions great.
Put it in water...won't start without a public address of non communicable words...floods...then slow start...ahhhhhh. Got it running.
Okay let's put it in gear....here we go....whooooooops....no throttle power...oh....yeah...let's Dr out here in front of the launch with the wind and choppy water.
Drift away for 10 minutes...starts....oh...Bogs and dies at quarter throttle.
Okay...limp and drift... Idle speed...out of water...take it home.
Well...of course it starts and runs perfect in tank again....what gives, guys? I'm already in my late silver years...I want to relax on the water with my gal and a lure in the water.

 

[jimmbo]

Well, on the hose/test tank and in the water are two very different scenarios. The Water in the midsection/exhaust housing has a major affect on the engines ability to idle. Also an engine with a weak or dead cylinder will sound just fine on the hose. So...

First thing, a Compression Test.
Does the spark jump a 7/16" gap?
When you put the carbs back on after cleaning, did you ensure they are all fully closed at idle/low speed, and that they are properly synced with the Timing Advance? Do those carbs have an Adjustable Low Speed Mixture? If so, were they adjusted after the cleanings?
Is the idle speed set to spec(in gear, running on the boat?

 

[biggizmo]

All 3 cylinders at 120psi+
Factory engineered without individual low speed set screws.
All butterfly caps are fully close and synched.
I don't have and idle adjusting meter tool.
And the spark is strong and set to specs.

 

[oldboat1]

Need to measure spark with an open air adjustable tester (cheap item at an auto parts store). This measures ignition strength, and shouldn't be confused with spark plug gap. Tested spark needs to be strong (likely hear it) and consistent. It's possible to lose spark when components heat up or are otherwise weak -- referred to as dropping a cylinder.

On carbs -- Seafoam or sprayed-in cleaners aren't sufficient. You may be due for a full carb cleaning and rebuild (disassembly and soaking, careful poking and prodding of all openings with soft wire, carb spray to rinse).

(from one silverback to another....)

 

[racerone]

Does the spark jump a gap of 7/16" on each lead, yes or no ?-----No need for an " idle adjusting tool " on this 2 stroke.----Might check the flywheel key too.

 

[fireman57]

Are yo u positive you put the carb linkages on correctly when you redid the carbs? It is easy to put them back on wrong.