Mercury 70, full RPM > no thrust, slipping gearbox ?

[mervyn]

He Guys,<br /><br />I have a strange problem with my Mercury 70 +/- 1990.<br /><br />The engine is running fine, but when I try to run fast the motor RPM is coming up,<br />but I have no thrust at all, seems like something's slipping.<br /><br />- Inspected the propeller, which looks good, don't think there's any friction in it.<br /><br />Does anyone have an idea what could be possibly wrong ? (gear, cables ?)<br /><br />I suspect that the 'gas/gear' cables are not good 'tuned' so that when I am running on<br />more power, the gear slips back in 'neutral mode' could that be ?<br /><br />I would appreciate any help on this topic very much !<br /><br />thanks in advance !<br /><br />grt. Mervyn from Holland

 

[JB]

Re: Mercury 70, full RPM > no thrust, slipping gearbox ?

Howdy, Mervyn.<br /><br />Your symptoms are of a spun prop. The bond between the rubber hub and the outer shell of the prop has broken.<br /><br />Take the prop to a prop shop. Rehubbing is simple and relatively inexpensive.<br /><br />Good luck.

 

[mervyn]

Re: Mercury 70, full RPM > no thrust, slipping gearbox ?

He JB !<br /><br />Tanx for your quick reaction, only thing is<br />I took the prop to the dealer already and he<br />tried it on a 'fixed' shaft.. ( turning it an looking if there was any problem, the rubber seemed to be OK then.. ( although not sure..)<br /><br />I did not know that the rubber can be replaced,<br />good advice ! ( almost bought a new one )<br /><br />Any idea what it could be when it is not the prop ?<br /><br />tanx and the greeting from 'rainy' Holland

 

[petryshyn]

Re: Mercury 70, full RPM > no thrust, slipping gearbox ?

I agree with JB, the likely cause is a prop hub slipping. If the prop hub is OK, it is also possible that the control cables are out of adjustment, allowing the gears to barely mesh in forward. It is also possible that the sprag clutch teeth are worn off of the shifter hub and gear inside the gear box.<br /><br />*I would borrow another prop and try it. If same, check cable adjustments. If OK, check for filings in gearcase oil. Then she'll have to come apart....

 

[mervyn]

Re: Mercury 70, full RPM > no thrust, slipping gearbox ?

He Schematic,<br /><br />Thanks for the tips, I'll take (both) your advice<br />and first try another prop, and a after that<br />see if the cables are not fitting well..<br /><br />tanx a lot !<br /><br />grt. Mervyn