Outboard tune up

[Master of Bait]

Hey Anglers,

I hope everyone's having a good season so far.

I'm looking for some advice on tuning up my 1977(ish?) 25 hp Johnson Seahorse.

It's been sitting in my yard for 5(!) years (kids, moved to Florida, came back).

Local marine shops are backed up for weeks.

I haven't tested it yet, but feels like I need to do something(?) to it - it was running fine when I last used it.

Any suggestions on what I should do?

Spark plugs (clean or replace)? Spark plug cables? Change lower unit oil? Carburetor clean up? 

Any ideas on a place that would stock parts for an old motor like this one, or would I need to order through a marine shop? I'm in the GTA.

Appreciate any suggestions you've got.

Cheers,

MoB

Edited July 31, 2020 by Master of Bait

[Raycaster]

Just bought a "new to me" boat and the first thing I did:

90 minutes ($125 in parts):

Changed Oil and Oil Filter (4 Stroke)

Changed Fuel filter

Changed lower gear oil

Changed Plugs

Took Prop off and on to check for fishing line or junk.

Testing the engine saw the water pressure ok so I will put impeller job off till Fall.

I am NOT a professional (as shown on this board frequently) but they were all common sense jobs with a hint or 2 from Youtube.

 

 

[Fisherman]

A complete fuel system tune up, clean out the tank,  wouldn't be a bad idea to get a new hose and bulb.  Check the fittings to make sure they don't leak. Replace hose inside the motor cowl.  Take off the carb and do a complete thorough cleaning, replace gaskets and float needle and seat.

[Master of Bait]

Thanks guys - this is helpful, and generally stuff I can handle on my own.

Cheers,

MoB

[Master of Bait]

Hey guys, I've been working on the motor - all straightforward so far and parts mostly available.

Any recommendations on a fuel additive to add to the first tank I run?

[Fisherman]

58 minutes ago, Master of Bait said:

Hey guys, I've been working on the motor - all straightforward so far and parts mostly available.

Any recommendations on a fuel additive to add to the first tank I run?

Seafoam.  None of that stabilizer granola.

[greyhawk]

Sea Foam is a highly effective gasoline preservative stabilizer that both protects your vehicle while it's sitting and cleans the fuel system when it's running. Sea Foam is the most comprehensive cleaner for your vehicle.

[Master of Bait]

Great, thanks guys. Will see how she runs.

[Hack_Fisherman]

Lower unit oil and carb clean for sure. 

Fuel lines if questionable, super hard or spongy. 

Clean/replace and gap plugs.

Seafoam is something I’ve always used but I’ve heard others rant about how bad it and premium fuels are on 2 strokes YMMV

[Master of Bait]

Hey guys, awesome feedback, thanks for this. I did the plugs, lower unit oil, sea foam and fuel line, but I didn’t have time for the carb. Anyway, the engine fired up really easily and ripped across the lake. Then.... pow! I’m pretty sure the gears started Missing/slipping. Big jolt and then kept going, then big jolt again, etc. Bummer, cuz  it’s a much bigger deal than I had hoped for.

I’m gonna try again with this other little 5.5 seahorse. Will keep y’all posted.

 

[Hack_Fisherman]

That’s one of my favourite omc’s.

is it a 54 or 55? 

Its a really clean looking survivor

I’ve had a pair of 58 10’s, a 58 7.5 and I just sold a beauty running 57 18 hp Johnny.

Horribly dirty running motors though. 24:1

how do the coils look?  

Pressure can still work?

Edited August 14, 2020 by Hack_Fisherman

[Master of Bait]

2 hours ago, Hack_Fisherman said:

That’s one of my favourite omc’s.

is it a 54 or 55? 

Its a really clean looking survivor

I’ve had a pair of 58 10’s, a 58 7.5 and I just sold a beauty running 57 18 hp Johnny.

Horribly dirty running motors though. 24:1

how do the coils look?  

Pressure can still work?

These are great questions, and, to be straight with you, I have no idea(!) on all fronts. It was given to me by a neighbour. I'm going to try some of those basic steps discussed earlier and see how it goes. I'm really glad you mentioned 24:1, as I would have run it with the 50:1 mix I currently have in my tank! From what I can tell, the spark plug cables need replacing too. Do you think that is something I can pick up at a parts store, or more of a special order item?

Cheers,

MoB

[Hack_Fisherman]

I’d check the coils 1st. They were known for dry rotting and splitting apart. I’d check for spark first, then if not pull the flywheel and look at coils. If they look good, they will most certainly have been replaced. Plug wires might be solid copper core, not braid so I’m not entirely sure on that. (I could be getting that confused with other engines of the era.) 

The pre 59 OMC motors had bronze bearings instead of roller which is why the 24:1 ratio. (Pre 54 was 16:1 I think)

I’d suggest looking the pressure can over too. If its rusty inside or hoses rotted, coupler missing etc. You could put more $ into the motor and tank as a whole than you can recoup should you not want to keep it. (Been there) 

not trying to burst a bubble here. If it was running in recent years it could be an easy project. If sitting for 20-30 years it’s going to take work. And if it needs too much, it’s still a beautiful wall hanger/display. 

Oh and don’t dismay if the compression readings are low, these are low comp motors by design. IIRC they will still run well at 85 psi. As long as they are both similar you’re good. Long stored motors can actually come up a bit in compression after running with rings unstuck and seating again. 

 

Oh and bummer on the 25 hp. Maybe you can find another lower unit or someone might want that powerhead

Edited August 15, 2020 by Hack_Fisherman