1990 evinrude 70hp boggs down at high speed

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Dabomb1

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Jul 12, 2021
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I have a 1990 evinrude 70hp outboard that bogs down at high speed. I will take it out and one day it runs good and next time it will run good for awhile and then bog down. I have had the carbs cleaned by marine mechanic, replaced plugs, wires, coils, new fuel filter and primer bulb. It's been synced. It feels like one cylinder is not firing. If I prime the fuel bulb it doesn't do anything. I disconnected the heat sensor to see if it was grounding. Didn't help. The last time,from a dead start, all I could get out of it was about 2500 rpm at full throttle. Don't know what else to try?
 
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Crosbyman

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how long ago was the carb job done...you may want to ask the mecanic why all his work does not allow anything above 2500 rpm . was the engine tested in any way after his work you paid for ??

tank venting ok ? fuel supply restricted somehow ?
old style carb
you could always try a blast of carb cleaner in the HS orifice ( just unscrew the lower bolt) and.... low speed orifice while you are at it

blast in part 22... the air orifice for the LS circuit of the carb ... may not require removal just a good blast ...

wear eye protection ...tinted eyeglasses do not like carb cleaners... same for eyeballs

on the LS....screw needle count the turns out and reinstall with same turn count in
1650903492282.png
 
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jakedaawg

jakedaawg

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Intermittent issue is often electrical. Preform a spark check with an open air gap tester while it is runningbpoorly. While it is misbehaving try pulling the plug wire off one at a time with insulated pliers. Note any change or lack of change. You could have any of a number of components starting to fail. Coils, power pack, etc. Proper diagnosis is the key. Also check, clean, tighten, etc. all electrical connections. Look for bad pins in the amphenol connectors and such.
 
Faztbullet

Faztbullet

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Disconnect the org wire going into pack from heat sensor. If overheating or defective sensor it will go into SLOW limiting RPM to 2500
 
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Brandon2468

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On my 1999 90 hp Johnson I’m having a similar issue where one day it will run great and the next it will bog down and get worse if I increase the rpm. It never shuts off and idles without a problem. I went through the whole fuel system and ran it on an external tank but did not help. Heard people have problems with the VRO pumps but I have a feeling it’s electrical. My next step is going to be a new power pack and if that doesn’t work change the stator. Anyone know how to test the stator correctly on this motor? What wires to read from?
 
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Dabomb1

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I'm replacing the power pac as well. It's ordered, just waiting for it to come in.
 
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Brandon2468

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I changed plugs, wires, coils and power pack today went for a ride motor ran great no problems got it spinning to about 5k rpm didn’t hesitate at all. Shut the boat off started it back up got back up on plane tried opening it up to see if it would act up and the motor would not go passed 4K rpm with the throttle pinned. The bogging never came back but now of course this happens. Any ideas?
 
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Brandon2468

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Took the boat out a few times hasn’t skipped a beat since I did the work got it up to 4500 rpm and then tried to go to WOT but now the motor won’t spin higher than 4200 not sure if it’s one cylinder not getting spark or something completely different. Runs smooth but I’m not sure any help would be great
 
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Crosbyman

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I will take it out and one day it runs good

Q... what was "good" did the boat ever do rpms above 5000 ? before the bog down issue came up ?
 
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