Can't reach WOT RPM's after churning bottom

[kshelly]

1974 115HP Johnson. I hit the bottom of a soft, muddy creek and churned-up alot of mud. No damage to prop, no vibrations, etc., but now I hit about 4600 RPM's at WOT instead of my usual 5100. Boat also feels sluggish, obviously not putting out the power it did before I dredged the creek! Any suggestions on what I may have done or where to look for problems?

 

[ob]

Re: Can't reach WOT RPM's after churning bottom

First thing that comes to mind is to drain and inspect the lower unit gear lube.

 

[kshelly]

Re: Can't reach WOT RPM's after churning bottom

ob;<br />Is the lubrication in the lower unit that critical to performance? I would expect quicker parts wear, but not a loss of performance. But then again I'm just learning this outboard stuff

 

[ob]

Re: Can't reach WOT RPM's after churning bottom

Depends on what level of seal damage may or may not have occured during the churning episode.For instance ,if the gearcase is overwhelmed with water intrusion to the point of excessive overfill,it could possibly set up a hydraulic resistance or thick emulsification of lube causing rotational resistance.Man ,that was a mouthfull.<br /><br />Also check your throttle linkage and insure your carb flaps are still opening fully .

 

[kshelly]

Re: Can't reach WOT RPM's after churning bottom

Maybe a mouthful, impressive, though!

 

[kshelly]

Re: Can't reach WOT RPM's after churning bottom

Perhaps unrelated issue, but the engine also has a tough time at low RPM's doing the "no wake" routine. Engine stalls after burping & farting alot. After it stalls, it's tough to restart. At first I thought bad gas, but tried another tank with no help. ???

 

[DJ]

Re: Can't reach WOT RPM's after churning bottom

Take a look at the spark plugs. Is one or more real clean looking?<br /><br />If so, you popped a head gasket after that little run in with the mud.<br /><br />Been there, done that.

 

[1986mariner150]

Re: Can't reach WOT RPM's after churning bottom

You may have spun your prop hub. If it is having trouble planning and seems labored it is probably spun. You can mark prop shaft and prop with a perminent marker try to plane then check to see if your marks have moved, or pull the prop off and look at the edges where the rubber meets the metal for signs of slippage, usually looks kinda shinny like melted rubber. I have spun my hub without doing any damage to the blades.

 

[kshelly]

Re: Can't reach WOT RPM's after churning bottom

Did a compression check, found 3 cyl's at 125, one at 120. Put everything back together, went for a run. Reached WOT RPM's no problem. Go figure. Unless I had a loose plug wire, I don't get that one. Anyway, still can't get it to idle well. Stalled as I was pulling back into the slip. I was considering adjusting the idle screw, but though I'd get some input first...

 

[DJ]

Re: Can't reach WOT RPM's after churning bottom

erau85,<br /><br />Glad you fixed it.<br /><br />I'm still willing to bet you popped a head gasket. The leak can sometimnes be impossible to see. Especially if it is fresh. I had more than one act that way.<br /><br />Here's a tip. Retorque the heads the next time you warm the engine up. <br /><br />I would rebuild the carbs, unless it was done very recently.

 

[jim dozier]

Re: Can't reach WOT RPM's after churning bottom

Try bumping the choke when the idle starts to fall apart. If the engine doesn't have a choke use the primer or squirt some premix into the carb throats. If it picks up your idle mixture is too lean and you would need to enrichen the idle mixture adjustment screw. Best to get a manual to know what the initial setting (number of turns out from lightly seated) is supposed to be.

 

[Solittle]

Re: Can't reach WOT RPM's after churning bottom

You may also want to do a water pump. Grinding crud in the pump will yield a short life for the water pump and if it goes - - -