1974 mercury 1150 I6 Impeller change.

bassboy416

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Bought seloc manual and sierra replacement kit (gaskets and impeller without housing or base). While researching the procedure on this the manual confused me more than it helped. First, it is unclear how it all comes apart and what linkage might need to be disconnected.... I think I can figure that out though... Main questions... The manual says that the gasket is very difficult to get off once you remove the housing... They recommend a kit that comes with housing and gaskets already installed (at least thats how it sounded to me). I've never heard of anything like this. Next, they go into detail about replacing the base below the water pump. My particular motor has shim material and it sounds like a pain in the XXX to try and replace the "base". So heres my question... Can I just replace the impeller and gaskets as a regular maintenance item without messing with the base or the shims they speak of? Is there any advice you can give me as to how to remove old gaskets and get new ones properly seated... Then also, my boat seems like it should have the cam1 assembly on the lower unit. Would this mean I need to put the boat in forward gear before removing the lower unit? Also, totally unrelated but I've looked all through my manual for how to get my lower cowling off so that I can replace my 6th spark plug... Any help is greatly appreciated!
 

tlh 178

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Re: 1974 mercury 1150 I6 Impeller change.

yes, you can just replace impeller and gaskets. just look at the base while you have it apart. alittle trick i use on plugs, if you can get a swivel on the spark plug and get it loose. use an rubber tubing too remove and install new plug. on my optimax its the one on the lower left hand corner thats a bugger. rubber tubing works every time. once its broken loose.
 

racerone

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Re: 1974 mercury 1150 I6 Impeller change.

No need to remove the lower cowl to replace that #6 plug !!!!!---Use a different wrench perhaps ?
 

bassboy416

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Re: 1974 mercury 1150 I6 Impeller change.

I'm going to do the spark plugs this afternoon thanks for the help...
 

Chris1956

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Re: 1974 mercury 1150 I6 Impeller change.

To get bottom spark plug out, remove all other spark plugs. Now use an open end 13/16" wrench on it.

Drop gearcase with motor in neutral. It will make it a lot easier to install. There will be 5 lock nuts and a bolt hidden under the zinc anode. The anode will be removed with a thin wall 1/2" socket.

Replace the impeller, wearplate and the two gaskets, provided you do not have water in the gear oil. Snug the waterpump cover bolts down, but not too tight or the cover will crack.

The shiftshaft is a splined slip fit coupler. Grease shift splines and driveshaft splines before reassembly. You will need to turn the flywheel to mate the driveshaft splines. Use finger pressure only on locknuts, to install gearcase.
 

bassboy416

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Re: 1974 mercury 1150 I6 Impeller change.

Did this yesterday in an hour and a half... Went without a hitch... One question, why finger pressure only on locknuts? You're talking about the nuts that bolt to the studs keeping the lower unit connected to the rest of the motor?? I may have over tightened...
 

racerone

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Re: 1974 mercury 1150 I6 Impeller change.

Nuts are to be installed using the fingers.---That prevents cross threading them.------Still need to be tightened with a wrench.----Same goes for sparkplugs.-----Loosen with a wrench and take out by hand --then install with fingers and tighten with a wrench.
 

Chris1956

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Re: 1974 mercury 1150 I6 Impeller change.

I recommend finger pressure until gearcase is mated to midsection. That way there is zero chance of misaligning the splines on the driveshaft and ruining one or both of them. After it is mated, tighten the nuts and bolt securely.

I should have been more clear.....
 

bassboy416

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Re: 1974 mercury 1150 I6 Impeller change.

Thing is.... This might be completely relevent to the situation... The dissassembly of this particular lower unit from the rest of the motor was difficult... It took some working it to get it do drop unlike my chrysler motor... it got to a certain point and then dropped out easily.... Re-installation was the hardest part.... I was told never to force it in so we did it several times... It would get close, then I would rotate the flywheel and it would get within 1/4-1/2 inch of mating but wouldn't mate easily. We did this several times, wiping grease off of the spline and shift mechanism each time to ensure there was no pressure keeping us from being able to do the job. We would feel a distinct difference when the flywheel got to the correct position... The lower unit would rise up within 1/4-1/2 inch of being perfect and get stuck... We would put it in gear and try turning the propellor and it seemed that the splines were connecting because in forward, the prop would click when spun in one direction and wouldn't spin the other direction... in reverse, the prop wouldn't spin in either direction.... in nuetral, it would spin easily... Didn't like the click in forward but tried to look at what exactly was in the way of the unit sliding easily into position... Upon further inspection it seemed as if the gasket that mates with the exhaust was a very tight fit. This area appeared to be the fulcrum of the problem... Both sides would slide in further and the middle wouldn't... The driveshaft seemed like it had already slipped into place a while ago and the gears seemed to affect the spin of the prop so we decided to try to tighten nuts slowly to make sure that there was no excess pressure that would indicate a problem... It easily tightened up evenly with a wrench for the last little bit and snugged up nicely... Because it was a pain to get off, I am hoping that maybe it is just a tight, sealed fit, but I am definitely concerned that I might have messed up... We ran it on the rabbit ears and it shifted into both forward and reverse and spun the prop... It spit out a nice healthy stream of water... I want to take it out saturday... Should I be concerned? I have time tomorrow to take it back apart if needed....
 

emckelvy

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Jan 16, 2004
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2,506
Re: 1974 mercury 1150 I6 Impeller change.

The exhaust-tube-to-gasket is always a snug fit, it does help to grease-up the inside of the gasket and the outside of the exhaust tube. Then the tube slips into the gasket with a lot less pressure.

Another thing that happens is the gasket will tear or warp inwards, where it'll interfere with the exhaust tube being fully seated. Or, you'll get salt/debris built up between the gearcase and the gasket. I've seen extreme cases where the buildup was so bad that it locked the exhaust tube in place. Not a fun one to get apart! The fix for that was to pull the gasket & scrape out all the crud, so a new gasket would fit correctly.

I'd think that as long as everything snugged-up well and you didn't have to "reef" on the bolts/nuts to get there, no nasty cracking noises and everything works as it should, it oughta be OK.

Probably a good idea to check those areas out carefully when you do the next impeller replacement, maybe plan on a new rubber gasket. A coating of Permatex #3 will stick the rubber to the gearcase and prevent corrosion buildup. Apply Mercury Anti-Corrosion grease to all studs/bolts/exhaust tube/water tube/etc (or a good waterproof boat bearing grease), and it'll all go together nicely & (more importantly) come apart easily the next time!

Cheers.........ed
 

bassboy416

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Jul 9, 2013
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Re: 1974 mercury 1150 I6 Impeller change.

Tested on the water today and all is well! thanks for your help!
 
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