engine is bogging down

[psvaj]

I have an early 80's Johnson 90hp VRO fitted to a starcraft boat. Just recently I noticed that the boat will plane out normally but soon after planing the engine will lose most of it's power and come to a slow crawl. It doesn't die, it just goes really slow. You can feel it lurching forward as if it wants to go faster but it never does. The engine sounds really funny while it is doing this. If I come to a complete stop and then get back on the throttle the boat will plane right out but bogs down again. It starts up fine and idles fine too. I will be checking the spark plugs today for any signs of crud. Could it be bad gas, primer bulb, gas lines, fuel filter, or expensive engine problems? Any help would be greatly appreciated.

 

[Daniel Beckman]

Re: engine is bogging down

Sorry this will not help you i guess.<br />But do you think we got the same prob?<br />Here is mine:<br />92 john fastrike 175 v6<br /><br />The engine does not run to hot the temp gauge shows normal temp (dont get any overheat alarm).<br />It drops power exact at 4800 rpm. Im turn it back to idle and it works perfect up to 4800 again.<br />When it have drop the power it kicks up and down with short rpm peaks trying to get power again.<br />Have checked everything with fuel restrict.<br />Checked plugs.<br />Do not get any fuel restict alarm.<br />at 4500 rpm i can run all day without any prob.

 

[psvaj]

Re: engine is bogging down

Sounds about right but I'm not sure what my rpm's were doing though. I did check the spark plugs and 3 plugs of the 4 were black with a thin coating of oil (the other one looked fine). Checked the fuel filter and that looks clean. At the same time, I pumped the primer bulb and noticed that gas was going into the fuel filter bottle but it wasn't filling all the way up to the top, which is where the pickup tube is located. Is that right? Anyway I checked the fuel line coming from the gas tank and it looks cracked and dry rotted. There is also another longer hose that was dry rotted pretty bad (it's the one where gas will spill out of when you overfill the gas). Lastly, I noticed that the propeller is very loose and will move in a forward and backward motion about 3/8 inch. The nut and cotter pin are as far back and tight as they can be but there is a big gap between the nut and prop housing where you can still see the spindle. Could this be the culprit?