Fuel Pump Problem?

Cromagnon

Cadet
Joined
Jul 28, 2016
Messages
12
I have a 1990 Evinrude 40 hp outboard tiller with problems. Symptoms started with it occasionally stopping while trolling. Would have to give it more throttle to keep it running at low speeds. Then the symptoms progressed to bogging down at wide open throttle on some trips. Now I can’t run at anything above trolling speed without it bogging down. It has a VRO system that has been disconnected. I replaced the fuel hose, put in new spark plugs, changed fuel filter, rebuilt the carbs (they looked clean), and started with new gas. The motor has run very well for the 3 years I have owned it until this started. I don’t want to replace the VRO unit as it is an expensive part ($500). I see that some people have removed the VRO and just added a fuel pump for much less cost. Do you think this is a fuel pump issue and how could I diagnose it? Could it be something else? Any advice would be greatly appreciated.
 

jbuote

Lieutenant Junior Grade
Joined
Aug 17, 2016
Messages
1,001
Still pretty much a newbie myself.
The little knowledge I can offer, is to try squeezing the primer bulb when it acts up and see if that helps.
Let these guys know results of that.

With what you've described so far, I think I'd also go back to the beginning and do a compression test and spark test with adjustable open air spark tester set to 3/8" gap if I remember right. Others can confirm or correct the proper gap for that.

This is to make sure no major issues are starting to happen.
If nothing else, it'll confirm a good base health of the engine.

Let them know the results compression and spark tests too.

$0.02
 

Cromagnon

Cadet
Joined
Jul 28, 2016
Messages
12
I have tried squeezing the primer bulb when it acts up and it doesn’t improve. Bulb stays somewhat firm while motor is running. Thanks for responding.
 

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
I take it you're running 50:1 through the existing VRO pump, with the oil line plugged and the harness disconnected.

When you disassembled the carbs for rebuilding, you must have removed the slow speed mix needles. Have those been properly reset (carbs "dialed in")? Part of the testing requires that the motor throttles up without stumbling -- back pressure is required (can't adjust on muffs). The roller assembly on the lower carb has to be adjusted properly so the carbs open at the proper timing advance (the "link and sync").

Operating temp. has to be on point -- about 140F. 160 is too hot, but it could be running cold if the t.stat is open or missing.
 

Cromagnon

Cadet
Joined
Jul 28, 2016
Messages
12
I am running 50:1 through existing VRO. I did not remove the slow speed mix needles on the carb rebuild. The motor is acting up the same after the carb rebuild so I’m guessing the carbs aren’t the issue. Thanks for your response. I probably need to take it to a mechanic to diagnose and fix as I have minimal mechanical experience.
 

jakedaawg

Rear Admiral
Joined
Jun 26, 2012
Messages
4,275
Step 1: compression test, post results.
step 2: open airgap spark check set at 7/16" with appropriate tester.
step 3: fuel sample into clear jar, even if it's new fuel, even if you dont want to...
 

Cromagnon

Cadet
Joined
Jul 28, 2016
Messages
12
I just just checked the VRO and it had been reconnected by someone. I’m not using the VRO (mixing 50:1). Would the VRO being connected cause the bogging down at open throttle?????
 

Tim Frank

Vice Admiral
Joined
Jul 29, 2008
Messages
5,333
I am running 50:1 through existing VRO. I did not remove the slow speed mix needles on the carb rebuild. The motor is acting up the same after the carb rebuild so I’m guessing the carbs aren’t the issue. Thanks for your response. I probably need to take it to a mechanic to diagnose and fix as I have minimal mechanical experience.

If you did not remove the slow speed needles and also the welch plugs to clean the small channels behind them, you may be gilding the lily a bit by claiming that "the carbs were rebuilt". I do not even think you can claim that they were cleaned without those steps....even if "they look clean".
As far as "guessing that the carbs aren't the issue", I would respectfully disagree.:)
I would suggest that you buy an OEM manual specific to that motor and R&R the carbs again following its instructions..
Pay particular attention to the HS orifices and make sure they are full diameter.

I just just checked the VRO and it had been reconnected by someone.

:confused::confused: Ummmm....who else works on this motor without your knowledge?
 
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