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· I Love microskiff.com!
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Discussion Starter · #1 ·
Good afternoon!

I have a early 90's 8HP Mercury Mariner. Overall the engine runs really good, however I have noticed when I run anywhere from 75%-100% throttle, it begins to slip. I can hear the engine grow louder, but it begins to slow down.

I typically slow down when it starts to do it and putt my way in. It also happens periodically. Could it be my prop? I appreciate any advice or suggestions.
 

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Post a pic of the prop. Sounds like the prop may be damaged causing cavitation. I'm thinking if the boat typically planes at 75-100% throttle (less torque required) and it aint slipping out of the hole (most torque required) then the rubber hub should be good. Did it ever run without slipping or has it always slipped?
 

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Discussion Starter · #4 ·


A picture of the Propeller, before dissembling.



Top nut off.



Second "washer" nut off.



Propeller off.



Final bottom washer off.



All pieces shown.

Is it strange that i'm not seeing a rubber hub what so ever? I will say this is a cheaper replacement propeller (Solas). When I first replaced it, it never slipped. However over the past 6-7 times running full, it has began to slip. I appreciate any advice.  Please let me know if I should take any additional photos.
 

· 01 Hells Bay Guide.07 ECC LOSTMEN-sold
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From the wear marks. Looks like hub slip to me. As in the once enough torque is applied the rubber hub will allow the the shaft to spin in the the prop. That's why you hear the RPMs raise and speed decrease. Any prop shop can press a new hub in. Or it may be cheaper to buy a new one somewhere. Or upgrade to a SS prop.
 

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Discussion Starter · #10 ·
Oh man.

Well went ahead and ordered a new propeller, Mercury this time. Installed it and took it out on the lake for spin. Well lo and behold, this brand new propeller began slipping at full throttle. It seems like the engine begins to vertically shake some then RPM's fly while the boat slows. Very frustrated. Fellow gentlemen, any other ideas of what the problem may be? Prop shaft? I can also take more pictures if needed.

Thanks for all your help so far.

Whooper
 

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Discussion Starter · #12 ·
I was also looking into possible Cavitation issues. The only reason I doubted this at first however was because the boat ran fine many of times without the slipping/bogging. I could literally run WOT for a good 15-20 mins and then it would happen. Or yesterday for example I would run WOT for 2 mins before it began happening.

Has anyone had issues with Cavitation?
 

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Discussion Starter · #15 ·
Well thanks for all the tips.

I took it out yesterday and it ran fine at around 75% throttle. Honestly the engine is an old dog, and last thing I want to do is dump another $400 for repair. Ill just rock 75% till she dies!
 
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