1972 Mercury 800 80 Hp Lower unit possibly

[kjburr08]

Well I took it out to the lake today seeing as it started up here in the yard and what not. Got it off the trailer, it fired up and backed it out in the water. Circled the lake a couple times and it was moving along pretty good, but I did have to use the idle lever for neutral to get it to rev and move faster. It seems there was slack in the throttle forward where I would go forward and it not do anything. So I circle around and stop to pick up my dad because at this points thinks seemed somewhat ok. Pulled up to shore put it in reverse to back, back out to the water, I did hear a clunk pretty bad when I went into reverse. Started to go forward again and it just rev'd up and the motor wouldnt get any speed. It would slow move fine.. But when I tried to give it some power it would rev and not go.

Does this sound like a lower unit problem? I mean it circled the lake at pretty good speed a couple times. Could it be a way I have the throttle linkages hooked up? I just dont understand why 1 second I was scooting across the water and the next it not go. I have not been sure how the linkages go or if its pushing it in gear all the way. I can post pics of them or try to if that would help. Thanks guys I just hope its not the lower unit, but if it is let me know :-\.

 

[BR]

Re: 1972 Mercury 800 80 Hp Lower unit possibly

Sounds to me as though you may have spun your prop. Easy thing to check first before assuming it's a lower unit problem.

Good luck!

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp Lower unit possibly

The prop is still intact good. I mean when I try to turn it in nuetral it spins freely, forward it spins 1 way, reverse i dont think it spins. The motor was blowing blue smoke when running, i doubt that should have not made it run fast but it was doing that. Probably to much 2 cycle oil. It just seems wierd how 1 minute it runs good, although 1 thing I did notice that was funny was this, when I would give it throttle to go forward it wouldnt give it speed, also I had to give the secondary throttle(the control name is merc control standard I guess), but I would have to move the second control to get it some speed(this is before I went to shore and backed back out. Any other suggestions?

 

[Moody Blue]

Re: 1972 Mercury 800 80 Hp Lower unit possibly

There is something wrong with your control unit. You should NOT be able to move the fast idle lever once the motor has been put into gear. That lever is only operable when in neutral.

I second the idea that you have a spun prop. A spun prop has nothing to do with the movement of the prop relative to the gear selected. Your prop is constructed of two pieces, an inner hub and the outer blade assy. The two are connected together with a rubber bushing. It is possible that the outer blade assy has broken loose from the inner hub. The prop will still operate at low speed/load, but will "slip" over the rubber hub when subjected to high loads.

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp Lower unit possibly

How would I fix a spun prop, and how does this happen?

 

[kjburr08]

Re: 1972 Mercury 800 80 Hp Lower unit possibly

What would cause this to happen, something needs replacing?

 

[Moody Blue]

Re: 1972 Mercury 800 80 Hp Lower unit possibly

The props are designed to "break" before the more expensive LU components, that's the purpose of the rubber hub. Possibly the prop struck something when you went into reverse? They can be repaired relatively inexpensively compared to the LU.

Here is how to check for spun prop. Somehow make an alignment mark (paint line, scratch, marker etc) between the outer hub (blade assy) and the rubber hub. Now take the motor out on the lake and try to run it as you normally would. Afterward, inspect the alignment mark and see if the outer hub and rubber bushing are still in the same relative positions. If the alignment marks have changed position then you have a spun prop.