1998 50hp Evinrude S.L.O.W. mode help!

Spartan_1971

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Jun 5, 2017
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Hello,

I am new to this forum and this will be my first post. I will be as specific as I can with this post as I know the topic has been discussed elsewhere, but not with the identical scenerio. I will describe my problem specifically in hopes of someone pointing me in the right direction.

I have a 1998 50hp Evinrude motor. The motor will rev up both in neutral and in gear for about 30 seconds after a cold start. After approximately 30 seconds have passed, the engine will enter S.L.O.W. mode and only allow me to get up to 2500 RPM before reducing power to the engine as I increase throttle.

I have a good stream of water coming out of the telltale with the boat in the water as well as with hose connection to the intake. VRO is not enabled, as I mix the oil and gas myself. The audible and visual alarm beeps/lights are functional when turning the key to the on position for testing.

When the engine reverts to S.L.O.W. mode, there are no audible or visual alarms on the dash console. There is a tan wire with blue stripe coming from the temperature sensor located on the cylinder. This tan/blue wire is connected with a single pin plug rubber plug to a tan wire with no stripes located on the port side of the engine. I disconnected this connection ( and thus the temperature sensor ) and the boat still reverts to S.L.O.W. mode at 2500 RPM.

There is another tan wire on the starboard side of the engine ( not sure where it is coming from ) , this tan wire is connected by a single pin rubber plug to a purple wire ( again not sure where this purple wire goes ). When I disconnect the tan wire / purple wire connection, the boat will not enter into S.L.O.W. mode.

If this was a powerpack problem, wouldn't the problem start on ignition instead of after 30 seconds of warmup? Even though I have good water flow through my telltale, could I still be overheating? ( there is no temperature gauge on the instrument cluster ). What is the function of the tan to purple wire connection. I am stuck and hopefully can get some guidance in this forum. Any help would be appreciated.
 

Spartan_1971

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Jun 5, 2017
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I just bought the boat used. There is no oil tank reservoir and the previous owner confirmed that he mixed the oil with gas in the tank. I would assume that since the engine ran before, and there has never been an oil reservoir, that it has always been set up as non-VRO.
 

flyingscott

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Apr 8, 2014
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The fuel pump if it is the original VRO has it's own harness not the same as the tank.
 

Spartan_1971

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Jun 5, 2017
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flyingscott,

I guess I do not understand. I am sorry. I am pretty new to this. If the VRO was causing the slow mode, wouldn't I get an alarm on the instrument cluster. Either a light or a 10 second beep if was oil problem??
 

flyingscott

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Apr 8, 2014
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If anything was causing the S.L.O.W mode to kick in you would get an alarm. You are not getting an alarm so you need to check everything. Start with the fuel pump or it could be a bad pack,bad sensor or bad diode you have some testing to do.
 

Spartan_1971

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Jun 5, 2017
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Thanks flyingscott. I did a diode test and it tested out fine. Temperature sensor also tested ok. I have ordered a power pack that will be arriving tomorrow. I will post the results when I have installed and tested. Thank you for your input!
 
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