Johnson 150 Starts Out of Water but Not In Water

[Finns&Feathers]

I've seen similar issues to what I have, but not exactly the same, hoping somebody has some insight for me.
I have a 1988 Johnson 150 outboard, at the end of the summer I couldn't get it to start while going out fishing, replaced the starter and battery and it started right away on muffs. Brought it to the lake, and it wouldn't start with the motor trimmed down. My friend suggested trimming the motor up and it fired right up, I can trim the motor down and it will stay running without issue. After we were done fishing and the motor was cold, it did the same thing, wouldn't start trimmed down, started trimmed up. I've tried to replicate the issue on muffs, but it will start trimmed up and down while on muffs, it's only with the exhaust back pressure that it won't start.
I've gone through the carbs, checked spark plugs, verified no issues with starter cables, and I'm stumped.
Any ideas of what could cause my no start while the motor is submerged??

 

[exrex0015]

mine likes to start with trim at half and then i can lower it but mine has 3 exits for exhaust and trimmed all the way down covers all 3 trim at half lets one breathe and it fires ip

 

[racerone]

You are pushing key in and holding it in while cranking it over?------Step #1 is to post compression test results for this issue.-----Sounds like low compression in the CRANKCASE might be a issue.

 

[Finns&Feathers]

You are pushing key in and holding it in while cranking it over?------Step #1 is to post compression test results for this issue.-----Sounds like low compression in the CRANKCASE might be a issue.

Yes, key in to choke with fast idle bar up, fires up with the exact sequence out of water. I'm planning on doing an air gap spark test tonight and I'll get a compression test and post values when I get them

 

[racerone]

Maybe exhaust relief is blocked / plugged.----Or crankcase compression is low and unable to overcome water pressure.

 

[Finns&Feathers]

Maybe exhaust relief is blocked / plugged.----Or crankcase compression is low and unable to overcome water pressure.

What/where is the exhaust relief? I had a mechanic service the lower unit in the spring and it was around that time when I started having the starting issues. I was thinking of dropping the lower to see if the exhaust through the lower appeared clean and clear.

 

[Finns&Feathers]

So I did the air gap spark test set at 3/8" and couldn't get any spark from any plug wires, I switched to a spark plug, and again couldn't see any spark, until I pulled two spark plugs out to remove compression and let the engine spin up faster, and now I get a solid blue arc at 3/8" on all plug wires, I'm thinking maybe my budget starter isn't getting the engine up to 300+ RPM? Anything I should look at before getting a new starter?

 

[racerone]

There you go , get a factory starter.---Have battery load tested.

 

[brodmann]

Wow, so the starting system is capable of spinning fast enough to start until you put a little back pressure from exhaust? That's pretty interesting!

 

[stresspoint]

Wow, so the starting system is capable of spinning fast enough to start until you put a little back pressure from exhaust? That's pretty interesting!

that is not what causes the hard to start issue with a 2 smoke when exhaust is lower than the water level.

best / easiest way to put it out there is >pressures go all over the joint in the crank case/s , "usually ???" if divider seals are weak or low cylinder compression.

most motors have relief ports in the exhaust that overcome this problem, this can also happen on a healthy motor if "AS above mentioned" that these ports have been restricted.
most likely the cause since the lower has been recently worked on.

 

[flyingscott]

Edit

 

[ct1762@gmail.com]

aftermarket starters... always amazing why people will throw away $65 on a new one thinking its a bargain. a few missing flywheel teeth later and realize a OEM $15 brush kit and 20 minutes will have the original starter back to like-new conditions and issues disappear.

 

[racerone]

Brush kits from local starter / alternator shop were $5.00 for me.

 

[ct1762@gmail.com]

Brush kits from local starter / alternator shop were $5.00 for me.

even better

 

[Finns&Feathers]

Well I guess that was a good lesson to only buy OEM parts again, got the new starter and it turns over at what sounds like twice the speed, no starting issues again.

 

[racerone]

I went to an electric motor repair shop years ago.----Wanted to buy some " magnet wire " to experiment with rewinding Johnson / Evinrude starters.-----Fellow started to explain to me how to do it and dipping after winding.----I explained the type of work I had done in the past.-----He then replied ----" you know stuff , you won't have a problem doing this "

 

[ct1762@gmail.com]

Well I guess that was a good lesson to only buy OEM parts again, got the new starter and it turns over at what sounds like twice the speed, no starting issues again.

that would be the beginnings of the recipe for said missing flywheel teeth