Mysterios problem -79 80hp Mercury.

[Bjornis]

Hi!<br />Last trip the engine broke, i had just put it in water and drove for about 500 yards. It was like it went in to neutral, the engine reved but the prop did not spin.<br /><br />I killed the engine and checked forward/reverse/neutral by spinning the prop by hand and it feelt ok. Started the engine again and tried to shift, nothing happens (except engine starts to rev more). First i thought something happened in the gear box so i took it of yesterday to check.<br /><br />Emptied the oil (looks a little brown, maybe water...) and checked the magneto plug, seemed like normal amount on it. Tried the gears and felt for backlash and it feels ok. Turning the drive shaft turns the prop both in forward and in reverse. That tells me that there is no problem in the gear box, I am wrong?<br /><br />Any idea what the problem is then? Think gears ar ok, prop seems fine (rubber hub looks ok). Engine starts and sounds fine.<br /><br />Where should I look now???<br /><br />Would appriciate any thoughts.<br /><br />/Bjornis

 

[fishingdan]

Re: Mysterios problem -79 80hp Mercury.

It sounds like your lower unit is ok. I would look at the shift linkage from your control unit to your engine's lower unit. <br /><br />There are two cables running to the engine from your control unit. One is for throttle and the other is for shifting. <br /><br />Did the shift cable break or come loose on either end (engine or control)? <br /><br />Is your control unit stuck in the mode where you keep the engine in neutral, but can advance the throttle. Often used for cold starting. <br /><br />The shift cable connects to the engine shift linkage under the cowling on the left side of the engine. Can you shift it into fwd, neutral and reverse with your hand?

 

[Bjornis]

Re: Mysterios problem -79 80hp Mercury.

The shift linkage seems ok, when I use the control box to shift it get in to gears. When i try to turn the prop and the enginge is in forward it freewheels at one direction (like it should) and stops at the other direction, same whit reverse. And in neutral it freewhels both direction.<br /><br />But when i try to turn the direction that it shouldnt freewhel it should turn the cylinders if i can turn hard enough but it doesnt, it sorts of slide. I have to turn real hard but the cylinders never move, just slides.<br /><br />Thanks for the idea though but I dont think it is the problem.<br /><br />More ideas?<br /><br />/Bjornis

 

[andy6374]

Re: Mysterios problem -79 80hp Mercury.

Sounds like a spun prop. Mark the prop hub and thr prob, put the engine into gear. If the marks aren't aligned then you've got a spun prop. In most cases this can't be tested by simply spinning the prop by hand.

 

[Bjornis]

Re: Mysterios problem -79 80hp Mercury.

Started the engine tilted up (prop out of water), and the prop did not spin. I think in that case with no load on prop it should move but no. Can it still be spun prop?

 

[Bob H.]

Re: Mysterios problem -79 80hp Mercury.

"it sorts of slide". I suspect that it didn't go in gear when you started it tilted. Mark the prop and hub, drop in water, put in gear and give some gas. If the marks are no longer aligned replace the prop. The fact that "it sorts of slide" indicates a bad prop regardless of any other conditions.

 

[Bjornis]

Re: Mysterios problem -79 80hp Mercury.

Is there any other way I can try the prop? I have made the boat ready for winter (out of water) since whe got the first snowfall this week :-(.<br /><br />I think it got in to gear since when i killed the engine and i turned the prop it was in gear.<br /><br />The prop isnt used much, have used it 3 seasons and have never hitted anything hard with it.<br /><br />/Bjornis

 

[fishingdan]

Re: Mysterios problem -79 80hp Mercury.

I am sure you are well aware of this, but just in case I felt I should say it. Double and triple check and make sure there can be no ignition when you are turning the prop in gear with your hands. You wouldn't want that engine to start....<br /><br />Can you run the engine on a water hose with the ear muff looking things? If so, start it, put it in gear and see what happens. Even if the hub is spun, the prop should turn with the engine in gear and no load. <br /><br />I have only had one spun prop hub. The boat would still idle forward and backward with that prop/hub. When I advanced the throttle (in the water) it would start to slip, but the boat would still be moving forward.

 

[kchunn]

Re: Mysterios problem -79 80hp Mercury.

Sounds like spun hub to me also. I had same experience as fishingdan. Prop would spin at idle and move boat forward, but as soon as I attempted to throttle up, it would slip. You can have a new hub pressed in. It's not too expensive.

 

[Bondo]

Re: Mysterios problem -79 80hp Mercury.

I once had that Same motor,.. Do the Same Thing to Me,......<br /><br />It was the Splines that Stripped Out of the Crankshaft.................<br /><br />Back when it happened to Me,.... There was No Fix,...... A Perfectly Good Running Parts Motor,.......... <br />Hope I'm Wrong.........