115 v4 2 stroke runs rough when warmed up

Jdepoy

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Sep 22, 2024
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Hey guys, new to this forum and new to boating! I recently acquired a 94 four winns fling with johnson evinrude 115 engine. Im having some engine issues and I'm not sure where to look next. So the first time taking the boat out it performed great, planed oit quickly and nicely, git to about 38mph and had a blast, ran wot most of the time for about and hour and a half and then the boat died it started back up but wouldn't get up to wot without stumbling and dying again. After that i brought the boat back home and decided to do some maintenance on it. When it died it felt like fuel starvation so i rebuilt both carbs on it and threw a new fuel filter in it and spark plugs. It ran great at home idle fine, held wot fine. I put it in the water and it did the same thing as it did the first time just after about an hour, it ran fien at wot and them just suddenly boggs down and dies. Once it does this it gets hard to start and stay running im lucky if I get ¼ throttle out of it to get back to the ramp and even then it'll die sometimes. So I did have a small water leak from the adapter plate from the jet drive to the engine i figured that could be my problem it could be slowly heating up and getting to hot and loosing spark or something so I took the engine out and fixed the leak and took it back out and now it lasted about 15min up on plane at wot before it died and it seems this problem it just getting worse but it seemed fuel related so my grandfather had an old fuel cell from his old boat he let me use and I bypassed the vro and ran my own inline pump with regulator and mixed 50.1 in the tank. I took it out like that and only got maybe 5 minutes of wot before it bogged down and died. I'm pretty positive now it's not the fuel system it has to be spark related. Is there any way to test the power pack to see if it's getting hot and loosing power? Also side note of I'm in the water and put it in nuetral and rev it it usually has no issue revving up fine its mainly under load. And if I and moving at maybe 10mph and maybe ⅜ throttle it'll without touching anything it'll bogg down and them pick back up and then bogg down and pick back up. So I'm at a loss. Any diag help is appreciated!
 

racerone

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Some will argue.-----The first step in trouble shooting is a compression test.----Post the actual values.
 

Jdepoy

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Sep 22, 2024
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Some will argue.-----The first step in trouble shooting is a compression test.----Post the actual values.
Okay, I can do a compression test Monday or Tuesday, should I do the test with the engine hot or cold? I've never actually done a compression test, I've only worked in 4cyl engines and always done leak down test as I thought they were more helpful.
 

Jdepoy

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I agree, compression numbers and have you tested your overheat sensors and horn?
Okay, I'll do a compression test. And I havnt tested the overheat sensors but I did take my IR temp gun with me last time and when it boggs down and dies the cyl head and block are in between 145 and 160ish
 

Jdepoy

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Here is a pic of the plugs, im really leaning towards a weak spark when engune gets to op temp. Is there a way to test the power pack? Or just parts cannon and see what happens?
 

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cyclops222

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Those plugs are a good part of erratic engine power.
Install CORRECT new ones. Those may be wrong type.
 

Jdepoy

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Those plugs are a good part of erratic engine power.
Install CORRECT new ones. Those may be wrong type.
Those plugs have been in the engine for 2 months and have 3 runs on them, they are what the turbojet manual recommended
 

cyclops222

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Only time I ever saw 3 run times look like that. COLD running engine due to stuck open thermostat. My own engine.
 

jimmbo

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2nd Step: Does the Spark consistently jump a 3/8" Gap on all Plug Wires?

" they are what the turbojet manual recommended"

Turbojet Manual???
 

Jdepoy

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2nd Step: Does the Spark consistently jump a 3/8" Gap on all Plug Wires?

" they are what the turbojet manual recommended"

Turbojet Manual???
My bad, I should have clarified. The turbojet manual is the manual for the engine and jet drive in the boat. It's just a 115 johnson evinrude outboard mounted in the boat on a jet drive. Mines at the shop so I can take a picture of the page that recommends those plugs but this is what the manual looks like, and I'm not sureabout the plugs Everytime I've gone out on the water I havnt thought to pull the plugs and see what's happening with them after it's warm. I can this weekend and let you know.
 

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racerone

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The " turbo jet "------Is the V-4 outboard powerhead mounted inside those jet boats 30 years ago.----Marketed for about 4 years at the time.
 

Jdepoy

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Okay guys I'm back at it with my fling. I kinda lost time and interest last year so I just winterized it and put it away. But I just got it back out a couple weeks ago and am trying to solve my problem. My problem would be considered low power/ loss of WOT RPM. When I floor it it doesn't get full rpm it does get spark both at idle and with some rpm tho it is worth noting it didn't get spark on cyl number 2 once during testing but when I went to check I'm the could pack was sending power spark cane back and that hasn't happened again. So I have spark, I checked fuel the bottom carbs float was filling with gas but uve replaced it thats all good (fuel was coming out of the front of the carb) fuel pressure is 4ish ast idle and 7-10ish psi when given rpms. So I believe I have fuel. And it acts the same with the flame arrestor off and engine cover open so it should have air. I did re check compression and same as last year between 118 and 120 on all cylinders. Also if this helps at all. Out of the water I can get full WOT RPMs I just can't in the water. I did rebuild both carbs last year so they should be good. Does anyone have any ideas? I'm open to anything any other tests I can do. I'll try to attach a video i took so you can can see and hear. That's what I'm getting WOT.
 

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jimmbo

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Those Ignition Systems often acted up when they got Warm, then later when Tested back in the Shop, they would work fine. However intermittent Spark can also be caused by Corrosion anywhere in the Ignition, of internal Breakage of those wire.
Out of the Water, these things will appear to run fine, even if 1 or 2 cylinders is Dead, but a bit of unasked for Advice.
Keep revving the Engine under no load or out of the Water , and you will likely not have to worry about any further Troubleshooting...
 
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