Old 1973 Mercury Outboard (4hp) jumps out of water in REVERSE

Carl Wonderful

Carl Wonderful

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Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
1973 Mercury (Marine 40) 4 HP, 2 stroke, jumps out of water in reverse. at the lowest speed, I can sort of hold it down with one hand if I stiff arm it, lol... but any throttle at all and its out of the water and isn't really even functioning at that point.

I think there is some sort of lock that should engage when you put it in reverse, but I cant find any good info on my particular outboard. Anyone have and links or diagrams or anything to help me solve this. Makes docking a nightmare!
 
High Current

High Current

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Sep 11, 2022
128
Catalina 34 mk 1.5 Rockland ME
Sorry about the picture quality, but there’s a pin that slides in near the base of the mount. If you lift the motor and look up at it you’ll see the latch arm that grabs it and holds it down. It’s released by a little lever near the starboard mounting screw.

if yours is anything like mine (admittedly a 6hp but I think it’s the same design), after 50 years the grease has solidified and the latch doesn’t move freely.

1779584236363.jpeg
 
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JoeWhite

JoeWhite

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Mar 6, 2008
1,490
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
My brand new one did that ,9.9HP. It was an easy fix, adjustment. Put it in reverse gear and look at the mechanism that is supposed to lock in place while in reverse.
 
P

Project_Mayhem

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Sep 24, 2018
4,448
Catalina 30 MKIII Chicago
High Current said:
Sorry about the picture quality, but there’s a pin that slides in near the base of the mount. If you lift the motor and look up at it you’ll see the latch arm that grabs it and holds it down. It’s released by a little lever near the starboard mounting screw.

if yours is anything like mine (admittedly a 6hp but I think it’s the same design), after 50 years the grease has solidified and the latch doesn’t move freely.

View attachment 237867
Click to expand
Please do share more info on the electric conversion in a new thread!
 
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Carl Wonderful

Carl Wonderful

.
Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
High Current said:
Sorry about the picture quality, but there’s a pin that slides in near the base of the mount. If you lift the motor and look up at it you’ll see the latch arm that grabs it and holds it down. It’s released by a little lever near the starboard mounting screw.

if yours is anything like mine (admittedly a 6hp but I think it’s the same design), after 50 years the grease has solidified and the latch doesn’t move freely.
Click to expand
Be nice if its a simple fix and just gummed up. Just trying to get my bearings on what is what (get caught up on the names of things without a visual)...from what you mentioned. I've poked around a did some work to my Mercury, but I am new to these motors...and motors in general so forgive me for bein a noob. We all gotta start somewhere right...

Can you help me understand where and which way this "pin" slides in near base of the 'mount'?
- Does this pin slide in laterally?
- Can I see this pin while looking down at the outboard while its on my boat.. or do I have to take it off and get it up on a stand?
- The 'mount' is the bracket with the 2 clamps that holds the motor to the boats mounting plate, right?

"Released by a little lever near starboard mounting screw"
- Can I see the mounting screw while the motors still on the boat (in your circled red area)?
- Is the "lever" hidden up and under it?
- 'starboard mounting screw'.. out of the 2 clamps..this is the clamp on the starboard side, right?

So your saying that possibly, best case senereo, my latch is just siezed up by old hard grease. If I clean it out and get new grease on there it mught just start latchign again?

What kind of grease do I use?

Appreciate the help!! I'm lost here without it.
 
Carl Wonderful

Carl Wonderful

.
Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
JoeWhite said:
My brand new one did that ,9.9HP. It was an easy fix, adjustment. Put it in reverse gear and look at the mechanism that is supposed to lock in place while in reverse.
Click to expand
To see the latch moving... do I need to get the motor up on a stand to look up into it?

What was the cause/issue with your brand new one? Seized/gummed up or just in need of adjustment

How do you adjust it?
 
JoeWhite

JoeWhite

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Mar 6, 2008
1,490
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
I pulled the boat out of the water with my trailer.
Then put it in reverse gear. Then pull the motor away from the boat near the propeller. It should not pull away. There is a mechanism just outside of the lower that moves up and down when you put it in forward and reverse. As I remember it was an adjustment on a rod that had to be extended to lock in properly.
If you do not have a trailer then you will have to remove the engine.
The images you have posted are not where the adjustment is. Look at moving 3/16" rods just behind the lower.
Here is a link that might help.
 
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BigEasy

BigEasy

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Jun 21, 2004
3,091
Beneteau 343 Slidell, LA
Had a 50 HP Merc ( circa 1981) that had a similar problem. There was a bracket with a hook that swiveled down to engage a horizontal shaft similar to #9 in the schematic. The hook was either broken or bent that prevented it from engaging the horizontal shaft when in reverse allowing the motor to rotate upward when power was applied.
 
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Carl Wonderful

Carl Wonderful

.
Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
If I cant fix it right away...Any reason I can't cut and wedge a 2x4 in there (when docking) to keep the motor down?
 
JoeWhite

JoeWhite

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Mar 6, 2008
1,490
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
It was designed to be pulled up so that when you have it on a trailer you can lift it and keep it away from making contact with road.
 
Carl Wonderful

Carl Wonderful

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Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
Richard19068 said:
do either of these schematics look like your engine? They both have parts related to reverse locks.





Click to expand
This looks like the one... not sure if it matters but my serial number is lower than what is stated at the top. Mine is 3654641. I have never really looked up inside it yet, but it all looks very similar to mine, if not exact. I know mines a USA and 1 cyl and 4 hp so that must be the one,
MERCURY - 4 (1 CYL. PRODUCT OF USA) - SWIVEL BRACKET ASSEMBLY
 
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3

...3TacksontheWater

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Sep 17, 2022
193
Catalina 22 Oolagah
That last diagram has the parts, numbers 10 thru 26. Might I suggest you go to your friendly Mercury dealer who might have some small mercs up on a stand and you ask someone to show you the assembly. That will give you a good idea of what to look for and you can pick up some grease while you're at it.

George
 
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Richard19068

Richard19068

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Jun 11, 2004
1,905
Oday 31 Redondo Beach


 
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