800 Stringer - No reverse

I think this my first post here, but have been a bit of lurker lately and you guys are terrific.
I'm hoping you can help with my 1977 Century 20' bowrider with 190 HP OMC 800 Stringer.
Put it in the water for the first this spring and the engine ran perfectly.
It would engage in forward but not reverse.
The revs would be controlled normally (ie: more reverse, more rpms as usual) just no engage into gear.

I attached some pics to help... maybe it will.

Please type slowly cause I'm no mechanic. I can tighten things, spot a loose wire, take stuff apart but only til I get scared I can't put it back together. That's usually pretty early on.

Now for the sympathy part. This beautiful boat is on a DO NOT RESUSCITATE order. If I can't fix it myself, I can't put any more money into the boat, no money to buy new one, you see where this is going...

Thanks in advance.

I do not believe that is an " 800 " model.----It is the old electric shift.----------Find the wires going into the drive at the engine.----Check ohms on green to ground and blue to ground.----If both are the same then apply 12 volts to blue and see if it shifts then.----------If it does not shift you may have a broken tab on the reverse spring.

This is my outdrive. You say it is not an 800?
I was told by the marina it was. ??

OR Do you mean that the controls are not original?

If I do have a broken tab on the reverse spring, should I use the boat with forward only? Not ideal, but I'm supposed to take the boat Camping this weekend. Maybe two miles down the lake to the site.
When I tested it yesterday (first time out this spring) I did not use the boat except for running at the dock.
I trailer the boat so checking a bunch of things is a kind of big deal.

That does not appear to be an " 800 " drive !!-----Just the old electric shift.-----The 800 drives were not electric shift and came out in 78 I believe.

OK. I took it back down to the water and and tried the electrical things as you said and nothing.
Could you describe the broken tab on the spring? Where is it? on the outdrive? inside the shifter mech?
Thanks

It is in the lower, get a manual.

Yes you do need a manual. There's some tricks to taking this lower unit apart correctly or other wise it could get expensive.

You are incorrect Bobbie. 800's were built at least as far back as 1969, I have one with electric shift.

You are correct that it is probably the reverse shift spring on the propellor shaft or the reverse coil. The forward and reverse coils are different the springs are the same. See exploded views on this web site and elsewhere. When ordering replacements, check the prop-shaft for wear and replace as well.

You may not want to hear this, but this is an old technology stern drive system.
You may want to consider cutting your losses now, and buy a boat with a different stern drive system.

1978 was the year OMC first introduced the "400" and "800" designations when the hydromechanical drives were brought to market. Like "Iron Duke", it's one of those terms people seem to like and so apply to everything similar.

1964-1977 drives were simply referred to as "The OMC Sterndrive"

Technically 400 and 800 series drives all have splined propshafts, but the terms have become somewhat synonymous with "stringer".