1976 sea sprite mercruiser 120 hp i/o need help.....

powell0819 · Mar 7, 2012

we have a 76 mercruiser we have been trying to repair after alot of money and time engine runs but dies when shifting from forward to n or from rev to n and the carb was rebuilt and adjusted spark plugs new and tested discap new and tested and same with wires, have recently been told of something like a kill switch for when shifting but still confused and after this is fixed have more q about steering, throttle and shift adjustments, steering cable freeplay and tension and my enemy tilt trim pump leaking

...... please help me before wife kills me:facepalm:

Don S · Mar 7, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

Very common problem when the lower shift cable becomes stiff in it's operation.

powell0819 · Mar 7, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

it shifts fine just dies once in N , we have just been told of that there is a kill swith on it that makes the engine stall for a split second when shifting to make release tension on the gear so it comes out easier but do not know how to adjust this and cant aford to take it to the shop, trying to get this thing up to par for snagging season here on the 15th, if anyone has helpfull advise would be very thankful

Don S · Mar 7, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

Sure, it will shift fine as far as feel goes, it's what the shift interrupt system feels that counts. If it stays engaged to long, the engine dies.
Read this thread, it will explain the shift interrupt system and you will better understand what the problem is.
http://forums.iboats.com/showthread.php?p=1930449#post1930449

powell0819 · Mar 7, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

ok thanks gonna take a look now on that forum

powell0819 · Mar 7, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

ok that exsplains alot but im not that smart , it dies in water under a load and not on muffs , so how do i adjust this out on the water or what all do i need to replace. and that post was very helpful thanks

Bondo · Mar 8, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

powell0819 said:
ok that exsplains alot but im not that smart , it dies in water under a load and not on muffs , so how do i adjust this out on the water or what all do i need to replace. and that post was very helpful thanks

Ayuh,.... I'm bettin' it'll behave, right after you install a new lower shift cable....

dubs283 · Mar 8, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

powell0819 said:
it dies in water under a load and not on muffs

there is no load on the prop when running on muffs so the interruprt switch does not engage - it is designed to work with a load on the prop

there is no adjustment for the interrupt switch, you adjust the NEW cable you are going to install to the dimensions in the OEM manual, there is a new V-spring you should install too, this will help the rocker for the interrupt switch to move better

powell0819 · Mar 8, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

Alright that clears up alot, thank you. Watched a youtube video a few days ago that showed the guy bending a metal wire that he said was the shift interrupt and he said thats how you adjust it so we were pretty confused. Wont really be going there for advice anymore. Thanks again!

powell0819 · Mar 9, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

after taking the lower unit apart and replacing the impeller we noticed the weep hole was filled with mud and rocks all the way to the shift shaft really bad but after a few hrs got it all cleared out and reassembled . could the rocks and bud built up that bad have caused the cutting out when shifting to neutral or are we still looking at the shift interuptor, taking it to lake tomorrow and will see how it does

Don S · Mar 9, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

The weep holes and mud in the exhaust passages are not your problem. You don't have a shift interrupt switch problem, you need a shift cable.

powell0819 · Mar 9, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

were do you suggest ordering one from ? and we will need the manual to go by on putting it on right?

dubs283 · Mar 10, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

powell0819 said:
were do you suggest ordering one from ? and we will need the manual to go by on putting it on right?

you can probably get one here on iboats, otherwise i would recommend getting an OEM one from your local merc dealer

yes, you will need a manual to install it and adjust it properly

you may need to start a new thread asking for the manual for your engine/drive - judging by the year in the thread title you need manual #2

powell0819 · Mar 23, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

UPDATE.... we found the online version for our motor here in the stickys , adjusted the carb to specs in manual,repaced distributor cap, set the points gap and dwell, set the timing to specs and the ticking has stopped along with the rough idle. also the engine now has more power than we have ever seen before and no longer has trouble shifting into forward gear not sure why but it seems to have fixed itself. thanks to everyone here on these forums we finally have this baby flying on the water, thanks everyone

powell0819 · Mar 23, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

also does anyone know if there is a kit with the gaskets and seals for our tilt trim pump cant seem to find one and dont have the money for a new one way too $$ ,thanks

Pete104 · Mar 23, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

There are 4 o-rings @ the control valve on that unit. Shipping on 4 o-rings, I'm sorry, just not right! Are you sure the hoses aren't leaking? You have about 10' of hose with 6 fittings inside & 4 outside.

Ryanlewis2010 · Mar 24, 2012

Re: 1976 sea sprite mercruiser 120 hp i/o need help.....

i have a working trim pump for that era just one of the lines at the trim sensor broke not a bad fix if all you need is the pumo. if you want the info im sure i could make a deal with ya let me know. Its for a mc1 drive which is what you should have don maybe you could clear that up. let me know by pm.

1976 sea sprite mercruiser 120 hp i/o need help.....

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