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Engine bogs down

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Bassman6176

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Have a 1992 70hp Evinrude that bogs down when I push down on throttle. I have rebuilt carbs, changed plugs and fuel filter. When I pulled the carbs the bowls were very clean. No trash in them. I did have to adjust the floats but other than that they were good. All my fuel lines are good and I have good compression. I have had two shops look at it and the boat seems to run just fine. When I get it on the water it runs fine for an hour or so and then it just decides to bog down when I put it in gear. It idle's ok. I have even put a new line from tank to engine. I had one shop tell me it could be the power pack but after he checked it he said it was good. I am at my wits end! Any suggestion at all will be considered. Thanks for help!!
 
Its freshwater. But water pump is working great. Not getting too hot. I just have a feeling it is something electrical and can't figure it out. I took it to two different shops and it will run just fine and runs fine at my house. Even if I let it run for a while and get to operating temp. But when on the water it will run fine for the first two or three times around the lake and then it just decides to start bogging down. I have had this boat for two yrs and no problems until two months ago. The first shop thought it could be my power pack but he said it seemed to be fine. So frustrating.!!!!!
 
I haven't changed thermostat. It's at least two yrs old cause that's how long I've had the boat. And I know the stator is ok. The shop where I originally took it checked it for me. I use maintenance free batteries. Could it possibly be the fuel pump? I obviously am getting fuel but is it supposed to be putting out fuel at a certain pressure? If so, how can I check that?
 
The shop I originally took it to checked the stator when they checked the power pack and said they were both good. It is strange to me that the boat only bogs down under load. In other words it runs fine at the house with the muffs on but bogs down only at the lake.
 
Bassman, you still don't know if you have a fuel or spark or temperature issue. You need to troubleshoot that first.
1) Make sure the overheat alarm is working. When you ground the tan wire coming off the cylinder head, the buzzer must sound.
2) If you can hold your hand a few seconds on the engine (thermostat housing on top of the cylinder head) when the engine bogs down, temperature is ok.
3) Hook up a timing light to one of the spark plugs and see if the spark becomes irregular/intermittent.
4) Try pumping the primer bulb and see if the engine picks up.

It's not uncommon for a powerpack to produce those symptoms you describe. Especially the fact that it occurs after an hour or so.

Yes, you should use an old style battery with your motor. But they are hard to get and for you not really necessary since your 1992 70hp already has a regulated charging system.
 
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