Fishing year over ? lost engine?

[wilts42]

ok here is the story, 1991 xr4 was noticed having a slight knock, you have to listen for it but its there. If motor is in gear and idle then I punch it it will knock? as the motor warms up it a little more noticeable. One month ago we ran over a small flat in the river that caused the motor to bounce up a little and put a couple little bends on the prop, about a silver dollar size. Two small hammers made bent them back. That is one possible cause, the other is the following. During a tournament we noticed this small knock, yesterday we drained the gas, putting in high octane gas (thinking it might of been detonation) while idling without covers I noticed fuel coming out of a small 1/4 line going into the block. It was small and going into the alum. block. I thought it might be a fuel return line. We fixed the leak and the motor still had the same sound.
We go home and I do a comp. test and all holes are blowing 120 psi even the one that the fuel line was next too. I thought we starved that cy. of gas and burned up the rings. I have been reading post all morning with people talking about tightening lower gear case, de-carbing the motor and others. The lower oil was changed before the season and this boat only has 250 HOURS on the whole boat. Where do I go from here?

 

[Dallenx]

Re: Fishing year over ? lost engine?

Mechanics stethoscope and try to hear were it's coming from.

 

[wilts42]

Re: Fishing year over ? lost engine?

145 people and nobody has ran into the same situation....... this must be bad. I just can't imagine the motor only having 250 hours and having a bad bearing

 

[Texasmark]

Re: Fishing year over ? lost engine?

What kind of prop hub do you have? If plastic, have you pulled it and examined it for cracks? Presume prop is SS. If you bent the blades on a SS prop, and plastic, it could have yielded on you. Prop nut torqued to 55 ft-lbs or better (55 is the torque spec on my 90)? When you goose it you are working the whole gear train, but the soft spot is the connection between the shaft and the blades. I really doubt a rubber hub would knock. Slip, but not knock. Other things might be a clutch dog rattle in the LU, loose flywheel (remote possibility), engine loose on the transom (remote). Your engine oiler is functioning properly???? I sometimes get a little rattle from my dog when I run my big prop idling. But I have a 3 cyl and you a 6 and I attribute it to the few cylinders and heavy, high pitched SS prop. If I change props to a lighter, shallower pitch it goes away.

Did you change props for a test?

Might run some Sea Foam for awhile and if you think you need a decarb. Sticking rings only thing I can think of as a correlation with that but it wouldn't hurt. Doubt you would have engine to mid section and mid section to LU loosening on that few hours. Lot of bolts there to keep things in place; course anything is a possibility. If the LU is moving against the mid section, you ought to be able to look at the interface seam and see signs of movement.

Everything from the flywheel down to the pinion on the bottom of the drive shaft are locked securely in place. Really no room for slop. Ticking like a lifter in a 4 stroke pushrod engine is just not part of it. I don't see a bearing ticking anyway. If dry it will squeal.

No idea as to the gas line you are referring to. Need faztbullet or steelspike to give you a heads up.

I'll think some more.

Mark

 

[oldman570]

Re: Fishing year over ? lost engine?

It could be that the small line is a balance/oil/fuel line to the crankshaft bearings and keeps them lubed. If the line was cracked for a long period it would not supply the bearings with the needed lube. JMO
Oldman570

 

[wilts42]

Re: Fishing year over ? lost engine?

It could be that the small line is a balance/oil/fuel line to the crankshaft bearings and keeps them lubed. If the line was cracked for a long period it would not supply the bearings with the needed lube. JMO
Oldman570

That's what I was thinking to on the small line. It was pretty small and I know gas was coming out of it, not sure if it was maxed gas but it wasn't straight oil. The problem with that line was where it pluged on the block there wasn't one on the top of the block just above the top carb. I thought it might be a fuel return line.

 

[wilts42]

Re: Fishing year over ? lost engine?

What kind of prop hub do you have? If plastic, have you pulled it and examined it for cracks? Presume prop is SS. If you bent the blades on a SS prop, and plastic, it could have yielded on you. Prop nut torqued to 55 ft-lbs or better (55 is the torque spec on my 90)? When you goose it you are working the whole gear train, but the soft spot is the connection between the shaft and the blades. I really doubt a rubber hub would knock. Slip, but not knock. Other things might be a clutch dog rattle in the LU, loose flywheel (remote possibility), engine loose on the transom (remote). Your engine oiler is functioning properly???? I sometimes get a little rattle from my dog when I run my big prop idling. But I have a 3 cyl and you a 6 and I attribute it to the few cylinders and heavy, high pitched SS prop. If I change props to a lighter, shallower pitch it goes away.

Did you change props for a test?

Might run some Sea Foam for awhile and if you think you need a decarb. Sticking rings only thing I can think of as a correlation with that but it wouldn't hurt. Doubt you would have engine to mid section and mid section to LU loosening on that few hours. Lot of bolts there to keep things in place; course anything is a possibility. If the LU is moving against the mid section, you ought to be able to look at the interface seam and see signs of movement.

Everything from the flywheel down to the pinion on the bottom of the drive shaft are locked securely in place. Really no room for slop. Ticking like a lifter in a 4 stroke pushrod engine is just not part of it. I don't see a bearing ticking anyway. If dry it will squeal.

No idea as to the gas line you are referring to. Need faztbullet or steelspike to give you a heads up.

I'll think some more.

Mark

Yes it was a SS prop and a 4 blade at that. I'm not sure if I have revved it in N to listen for the knock but in gear and giving some gas I hear it.

 

[adam98]

Re: Fishing year over ? lost engine?

I have a xr4... What crank case hose are you talking about. Whats the other side connected to. And where on the block. What do all the spark plugs look like. All look the same? And color? Wet or dry?

 

[adam98]

Re: Fishing year over ? lost engine?

All hoses to block are vents breathers, no lube and should only be air. If The vacum line off case going to fuel pump has gas in it that means pump gaskets are bad. I had to buy new carb Gaskets as I had weird random running issues. Bad stator and bad switch box. It ran with all this crap wrong

 

[Daniel1947]

Re: Fishing year over ? lost engine?

I am no where near the expert level you will find here on the forum, but I will make a quick point or two about detonation, if indeed that is what you have. 99% of detonation is caused by ignition (timing off or the advance not working properly) or fuel (bad fuel or too lean a mixture) That other 1% can be caused by many factors, carbon build up etc. All of these conditions lead to a higher than normal combustion pressure. A standard compression check won't show anything because it isn't checking ignition or fuel etc. I had a similar problem, couldn't figure out what the noise was in my 89 150HP BlackMax, would tap and go away, one day the motor locked up, pulled head, #3 piston burned. Just a thought, did you have the tap before you hit the flat and bounced the engine.

 

[wilts42]

Re: Fishing year over ? lost engine?

Ok,
Drained the Lower last night to find it dark and having shinny metal in it. I wiped the magnetic plug to find ALOT of metal shavings finely ground sticking to it. I think this might be the problem, is there a rebuild kit for the lower or is this just a bearing issue?

 

[Chris1956]

Re: Fishing year over ? lost engine?

Rebuilding gearcases is expensive and complicated. If you have the large gearcase (4-3/4" hub), replacements are avail from SEI. Used Gearcases are avail as well.