1980 70 HP Johnson Seahorse

MODEL #: J70ELCSA

I bought a Bayliner with this motor on it, and it looks very clean - I had it on the earmuffs and it ran fine. Maybe a little cold blooded. I attribute that to the few moments I ran it on last-year's gas.

I opened it up, checked the plugs; they needed replacing - did that today. They were beyond worn (about twice as much as the recommended .030 gap - at least that's what the guy at NAPA told me).

OK, so my questions are pretty basic.

#1 - The fuel mix is simply 50:1, right? It's a single tank under the transom, and from what I've read through here, I believe it's 50:1.

#2 - Can I run seafoam or stabil through the gas to help "clean it up inside"? Will that harm the gas-oil mix? If so - how much should I add to the tank? If not, what's an alternative?

#3 - I'd also like to drain and replace the lower-unit gear oil. The marine shop has this (what looks like generic) marine-lower-unit oil, some 75-80W or some such. Says its good for OEM Johnson/Evinrude. Any concerns there? A friend said to get the motor exactly level, drain it, then fill it back up till its even with the fill screw hole. That sound right?

#4 - is it safe to put teflon tape on the fill-screw and drain-screw screws for the lower gear unit after I've done the oil replacement?

If I had any complaints about the few moments I ran it, I'd say it was either starving/flooding - sort of boggy. I'm going to attribute that to the crap gasoline, the very-worn plugs, and probably a fuel filter that needs love. Tomorrow I'll replace the fuel filter, as well as check the fuel fittings to make sure there's no leaks.

All in all, it ran well, and started right off. I can't complain one bit. Just looking at this thing, it looks like a solid workhorse, and I'm impressed with the shape it's in for a 30 year old motor.

Re: 1980 70 HP Johnson Seahorse

That's a fine motor you've got. I've got a 1978. In regards to your questions:
#1 Yes, fuel mix is 50:1

#2 Seafoam is fine, follow the directions on the container.

#3 Doing a lower unit oil change is highly recommended. I use genuine Johnson/evinrude lower unit oil, but any would be fine, as long as it says outboard lower unit oil. Get yourself an oil pump, it'll make the job easier. you have 2 screws, one located at the bottom of the lower unit, and one by the Cav plate. DON"T unscrew the philips head screw located higher up the leg. Drain all the oil out, check if it is milky or not. If not, screw the pump into the BOTTOM drain hole, and pump oil in until it comes out the top hole, this ensures all air is out of the gearcase. Put the top screw back in, and as quick as you can, put the bottom one in after unscrewing the pump. a little coming out won't hurt anything.

*edit* if your motor is electric shift, you'll need lower unit oil specifically for electric shift motors
#4 I'd strongly advise AGAINST teflon tape. Get replacement washers/drain screw rings. The store here on Iboats has them

Re: 1980 70 HP Johnson Seahorse

Thanks, Topol -- I've got some gasket material, I can make a few washer rings out of it - or I'll see what the marine shop has when I go looking for an oil pump - hopefully those aren't too spendy.

Can anyone confirm that my spark-plug gap should be .030? I read on another thread for an 85HP was .040 and now I'm second-guessing the plug manual at NAPA.

How much lower unit oil can I expect the (long-shaft) unit to hold? I bought three tubes - the guy at NAPA said most folks buy two, as it takes 1.5 tubes. I figured I'd get more just in case most folks short-shafted it - if that made any difference.

Re: 1980 70 HP Johnson Seahorse

The oil I picked up for it is "Hypoid 90" by CRC. SAE 80W90 API GL-5. It's in a tube, and apparently screws right in - the directions say to stick it in the lower till it flows out the top. I guess that makes buying a pump a moot point. Might be a tad messy if I need more than one tube

Re: 1980 70 HP Johnson Seahorse

Topol, thanks again - I really appreciated the fast feedback. It's not an electric shift, so I think I'm safe with the oil I picked up.

To recap - follow-up questions:

1. Is the spark plug gap for this .030? (1980 long shaft 70HP electric start).
2. Any idea how much lower-unit-oil it'll take? I have three 10oz tubes ready to go (80W90, API GL-5, Hypoid 90 by CRC).
3. Any special oil I should consider, what people like best for the gasil mix? Or can I just get any two-stroke gas oil?

Re: 1980 70 HP Johnson Seahorse

Hey Zoob, sorry for the delay, busy with work and the kids. To answer your questions

1. Yes, .030" is the correct gap for your plugs. Manual says L77J4 plugs, which aren't around anymore, so use L77JC4 plugs.

2. Manual says 25.4 oz for capacity of lower unit oil, so with the 3 that you've got, you should be alright.

3. This is always a controversial topic. Some people swear by the genuine oils, others to the walmart brands. Given the age of the motor, you don't have to worry about voiding a warranty, so my advice is use whichever 2 stroke oil you please. Generally look for a picture of an outboard motor on it, or the words, and you should be ok. I run whatever 2 stroke oil is available at the gas station while filling. Be sure it meets TC-W 3 specs and you'll be fine. (it'll say tc-w3 somewhere on the container, either front, or maybe the smaller print on the back)

Hope this helps, any other questions, fire away, i'll do my best to help you out.

Re: 1980 70 HP Johnson Seahorse

Thanks again, Topol!

Re: 1980 70 HP Johnson Seahorse

Oooh, I guess I have one more question - and that involves the propeller. It's fairly nicked and dinged, and I believe I'll want to replace it. I read about making sure you get the right pitch angle prop -- any clue as to what mine should be? Again, it's a 1980 electric start (not shift) 70HP johnson, long shaft. Attached to a 15' Bayliner Runaway.

thanks again for all your help!
-Jason

Re: 1980 70 HP Johnson Seahorse

When it comes to props, i'm an amateur, only thing I can tell you is that I have a 13.75"x15" on mine. If you're happy with the performance you were getting before the dings and nicks, just replace it with your current prop setup. If you pull the prop off, it should have the dimensions of it stamped into a ring just outside of where the nut goes to hold it on. Hope any of this helps.

Re: 1980 70 HP Johnson Seahorse

Thanks again, Topol. The one that I have on now has a few dents and nicks, but it still moves the boat.

I changed out the gas and the plugs, as well as did the lower-unit oil replacement (g'lord what a mess that can be when you only have one tube ready to squirt). You were right, it took nearly all three bottles.

Fired it up this morning and it popped right off, went into idle immediately (versus a couple weeks back where it was sluggish and cold-blooded and needed warming before sitting in idle).

Maybe in the fall I'll do a carb-rebuild (not for any reason, other than onaccounta) if I'm feeling ambitious - but I'm crazy-pleased with how clean the inside of the hood is, all the original labels on the wires, walls, and hoses - and it runs just great right now.

Thanks much for all your help!

Re: 1980 70 HP Johnson Seahorse

My motor is insanely clean under the hood as well. Apart from the fuel line I replaced, everything is original, and crisp clean. In my opinion, I wouldn't do a carb rebuild until early spring right before you put the boat in the water again, but thats just me. Be sure and winterize your motor properly though. A full breakdown of what should be done and how to do it can be found IN THIS THREAD It comes from the top secret file in the Johnson/Evinrude repair section. In regards to how messy the lower unit oil change was... invest the 10 bucks for the pump and just make sure you get a big enough bottle of L/U oil and you'll see it'll be much cleaner/simpler next time. I personally change my L/U oil twice throughout the boating season and once more while winterizing. May be overkill, but I like to know that i'm not leaking water into the L/U. You May be able to have your Prop reconditioned as well, Had to have that done to mine, cost around $60. Alot cheaper than buying a new prop. Just something to consider. Any other questions you have fire away Always happy to help in any way I can.

Re: 1980 70 HP Johnson Seahorse

Yo got a killer good motor there take very good care of it.

In my opinion the 80s Jonnyrudes are the best engines on the water, they are simple as stone and easy to work on and any part you need is readily available.

I have an '81 50 with the original power head, still paint on the head gasket, and it still has 135 compression and runs like a top.

I change oil at the end of the season and check it though out the season every other trip by just cracking the bottom drain plug after the engine has sat for awhile, if oil comes out you are good, if it is water you know there is a problem.

One hting to keep the mess down when changing oil is to pop the top plug back in a turn or 2, keeps so much from coming out, I also get 2 quarts and fill one clear to the top so you don't have to stop, fills it the first time.

Re: 1980 70 HP Johnson Seahorse

After the first messy attempt, I did exactly that. Before I swapped tubes, I would screw the top one back in, letting it help keep the oil in - also had all three tubes cut and ready to go, made it a cleaner issue. I'll go get a oil pump and a big ol' bottle of LU oil for the next go around (I figure I'll change it out in a couple weeks to see how the oil is doing in there).

I was pretty pumped to finally get it on the lake tied to the dock yesterday. After a couple weeks of going over the boat and motor, earmuffing and testing the motor, etc. - when I was finally launching it, the motor wouldn't start. Starter spun but wouldn't engage.

Turns out I had apparently drained the marine battery - leaving an accessory switch on. The boat landing is only a mile or two from home, so I bolted home, stole the battery out of my other car, and brought in back and it popped off and I drove it to my dock. Put the marine battery on the trickle charger, and it's all good now.

As I was messing with all this trying to figure out what was going on, I saw the fuel line inside the head (the short hose that goes from the connector up into the filter) had a pinhole leak in it (which was made worse when I did the "what the heck is that" rub on it with my finger). I'll be replacing that today. For a temp fix, i just removed the connector on the fuel line from the gas tank and connected it directly to the filter (no clamps either, just needed to get it to my dock).

So yeah, a dried up short fuel line, and some ancient spark plugs were my only problem with this motor, otherwise she's the tops. Very, very pleased.

Here she is:

Re: 1980 70 HP Johnson Seahorse

Topol,

Here you go. A quick clip from the phone of the tough guy in action. On my 15' Bayliner Runaway (tri-hull), this beast rooster-tails at half-throttle. With just me in the boat, I can't go over that, the bow comes up too high.

Here's the short video:
http://b.planetzoob.com/images/MOV01384.mp4

Re: 1980 70 HP Johnson Seahorse

If the bow comes up try moving your trim pin towards the transom a hole or two. Should hold the bow down and allow you to run WOT (wide open throttle) with even just you in. Move 1 hole at a time and find your happy medium for your average use (Friends/family on the boat, or just yourself) sounds REAL nice though!

Re: 1980 70 HP Johnson Seahorse

I'll look, but I think the trim pin thing is already in the final position near the transom wall. It turns out that it only does that lift partially the way through power-up. I had a couple friends on the boat this weekend up in the bow seating and it lifted (not as much) but then leveled out when I got to WOT. WOT just took the four of us in that little boat and hauled like there was no tomorrow. It's plenty faster than what I'll ever need it for (unless I decide to go into some sort of smuggling cartel from one side of my lake to the other, and I need to outrun the lake full of lund fishing boats and geriatric pontoons ) I don't/won't try that just solo, though - last thing I want to see is a boat landing down on top of me. =)

I don't see myself doing WOT all that much (the boat will be used for fishing, puttering around for a nice scenic sunset relaxation, and pulling 9-yo tubers) - so I don't really have a reason to WOT it, anyhow.

I'm still very pleased. I was out on the lake for the last three days almost the whole time, sunrise to sunset. The first day was just puttering around, getting the feel for the boat, the motor, putting it through its paces, and building the trust in the boat and motor. She's a little bit of a gas pig, but that's probably just it running a little on the rich side, and I think I should be giving the carbs more TLC than I have (which is none) - my gauge on how much gas she should be using is pretty off, I've nothing to compare besides my little tiny 2-strokes (tiller, leaf blower, ice auger) - and I don't run those all day like I did this motor this weekend.

Still, very very very happy. Now I just need to slap on power trim so I don't have to keep risking a hernia trying to tilt the motor when I dock it at my dock.

I can't thank you enough for your help with it. I really appreciate all you've done. The 3-yo has aptly dubbed the little boat, "Rubber Ducky." (here's a better pic):

Re: 1980 70 HP Johnson Seahorse

Zoob, NICE looking boat. that bow lift you're talking about might only be the boat trying to plane out. Looks like you have a tri-hull which is a heavier boat by nature, and more resistance, although alot more stable with friends/family on board. (because it's basically flat across the front with "v"'s shaped into it 3 parts of the hull) whats the max hp rating of your boat? (found on a plate which includes your HIN)

Re: 1980 70 HP Johnson Seahorse

Topol, I believe you're right regarding the planing out. Each time I've pushed through the lift I feel, it does end up planing itself out.

The max motor rating is 70HP (lucky me, eh?). It's a 1980-81 Bayliner Runaway. It really does scream across the lake when I open it up with that motor.

I did luck out in picking up this little boat, it's very clean; in great shape. It's been out bobbing like a cork next to the dock, and isn't taking on any water. I rewired it (got rid of the 30 yo wiring in it), put new lights in - and added an automatic bilge pump - that's about all I did to it.

Re: 1980 70 HP Johnson Seahorse

any idea what your top speed is?

Re: 1980 70 HP Johnson Seahorse

Zoob said:

Topol, I believe you're right regarding the planing out. Each time I've pushed through the lift I feel, it does end up planing itself out.

The max motor rating is 70HP (lucky me, eh?). It's a 1980-81 Bayliner Runaway. It really does scream across the lake when I open it up with that motor.

I did luck out in picking up this little boat, it's very clean; in great shape. It's been out bobbing like a cork next to the dock, and isn't taking on any water. I rewired it (got rid of the 30 yo wiring in it), put new lights in - and added an automatic bilge pump - that's about all I did to it.

Click to expand...

When I finally get back to being able to work on my project (16.5-17' terrasyn panther) and get it back in the water, i'll post some pics of it. Lately been working, or working on the car, etc, and the weather hasn't helped any either seeing as all work is done outdoors,and mostly rainy weather. no garage If you've got nice weather your way do me a favour and send me a couple days of it happy boating!