Johnson 70

[reelfishin]

I am looking at a used boat with what I am told is an early 80's Johnson 70 HP 3 cyl. It's on an 18 ft boat and I was able to take it for a good long test run, ran it through about 4 gallons of fuel.
It started and ran great, all looks fine.
The engine has just had a rebuilt powerhead, the carbs rebuilt, all new coils, water pump, control pack and plugs, and the mid section and lower unit were gone through an just resealed.

I have owned all Mercury and Yamaha engines up to now. Is there anything that I should know about these engines before buying this boat? The rest of the boat is fine, I originally was intending to buy it only for it's motor and sell off the hull, but it's in better shape than the boat I was looking to repower and it's turn key ready to fish.
I did a compression check and got 145 on all three. I ran it for about 3 hours and all seemed great.
What kind of reputation does this engine have? Any thing I should be concerned with?

 

[tashasdaddy]

Re: Johnson 70

they are reliable engines, my understanding is, if they have a drawback, it's that they are 3 cylinder, the center cylinder gets hotter the the other 2, and if it has a cooling problem usually leads to a rebuild. 145 is great compression, that kind of fuel comsumption on an 18 is also good. the mercs inline also have the middle cylinders cooling situation. if it suits your needs, and reasonable priced. i say go for it. i had several mercs, but keep coming back to the omc family.

 

[reelfishin]

Re: Johnson 70

I am familiar with the 3 cylinder center cylinder tendency to get hotter, but I've had several Mercury three cylinders and got good service out of them. In fact, never had a failure. I flush my motors well after every use, change the water pump or at least the impeller every year, and keep them well tuned.
I think that I ran it long enough that any problems should have surfaced during the test drive.
The only concern is why it had to have a complete overhaul. I didn't want to buy it and find out that they had some known problem. I haven't seen may of these engines around here, the local dealers all have nothing but imports anymore.
The power head looks to be an exchange unit, it's got two little round telltale heat tabs stuck on it, and a small plate with both specs and a partnumber. I am not sure who rebuilt it.
It's got a new starter, it looks like all of the elecrical system is new, even the harness looks super clean. The lower unit is painted with somesort of marine paint, but the mid section and pan are painted sort of a gray green and look near new. The lower unit and bracket look like they were painted on the boat, as the bottom of the hull and transom are painted the same way, sort of a chalky white paint. The cover is original and has minor wear and a few chips, nothing major. I could repaint the cover, bracket, and lower unit and this would look almost new in and out.

I am more interested in the motor than the boat, but I may leave them together and sell my boat. I can't see taking the motor from a functional boat, especially one that is at least equal to or better than the one I was looking to repower.

It did seem pretty light on fuel, it did about 30 mph or so, maybe a bit more. I got on it a bit during the test ride, but kept the rpms varied since I pretty much figured that it was the motors break-in run.

The place that has the boat had rebuilt the motor for a customer who either never claimed it or wouldn't pay, I think they may have matched it to the boat. I don't think that the two were always together. The boat is newer than the motor, but in equal condition. I had asked how much for just the motor, and they said they were basically including the boat for free to get their money out of the motor. It seems like a good match to me and I will be picking it up Monday or Tues.
It should make a good back water fishing boat.
If I decide later I still prefer my old boat, I can still swap the old motor to that boat and use the 70HP on my old boat.

 

[whofan]

Re: Johnson 70

Back before fuel injection and four strokes. The Johnson 70 was one of the best motors on the water. When OMC first came out with the VRO oil injection they had problems with the motors that had it. Yours maybe pre VRO or the VRO could have been the reason for the rebuild.
I have a 2000 Johnson70 its been good although crude compared to whats come out in recent years.

 

[reelfishin]

Re: Johnson 70

I think this is prior to VRO, the cover is all white, with only the name Johson and a 70 on the back with a red and blue stripe.
It felt pretty strong for only a 70 HP, I was surprised at how well it pulled. I am wondering now if I could get by with a 70HP on my other boat, a 19' Renken open hull fishing boat? I had been looking for a 115 for that, but maybe a 70 would do the job and save me some fuel?

This is the cover style on my motor. I am guessing it's late 70's or early 80's? I actually think that this motor may be a combination of several years now, the pan and mid secion are gray, the lower unit and cover are white. The powerhead is light gray in color.

 

[kenmyfam]

Re: Johnson 70

The numbers from your motor will tell you its vintage.

 

[tashasdaddy]

Re: Johnson 70

you know if it runs good, meets your needs, and the price is right, go for it. i personally am a OMC, person, i find them easier to maintain myself, than the merc. i've had several mercs, and keep coming back to the johnny/rude. this very well may be a johhny/rude hybrid, as the parts were, 99% interchangeable. also that's why parts are still available.