Considering buying a 77 Johnson 70HP motor please help.

[mattzmojo]

I have a 15' trihull that has a 72 Erude 50hp motor, which I have fond feelings for due to being the same age as me and for its reliability but it is not quite powerful enough for my boat. I saw that someone was selling a 77 Johnson 70hp motor. It does not come with control cables.

Some of my questions are as follows:

• Is this motor reliable?
• Would this motor cost me alot in fuel compared to my 72 2-cylinder 50 hp?
• How hard will it be to find the control cables?
• How much deviation in pressure is too much between the cylinders? 1=150,2=145,3=150
• Are there any mounting issues that I need to think about-will it match existing holes?(I have never swapped a motor, pretty new to boating in general)
• This motor does not come with trim and tilt, do any of you know whether there is a way to install that later?

I appreciate any and all help and please feel free to give me suggestions.

 

[JB]

Re: Considering buying a 77 Johnson 70HP motor please help.

Ahoy, mojo.

Welcome to iboats.

* The OMC triple loopers are cousins to the twins and just as reliable.
* The 70s are economical, but it does take more fuel to make 70HP than 50HP.
* I think you can use the same controls that you use for your 50.
* Over 15% deviation would be too much. 150-145-150 is near perfect.
* Swapping a '77 70 for a '72 50 should be (I think) the easiest swap possible; just unhook the 50 and hook up the 70.
* Installing an OEM PT&T on the 70 shouldn't be a big deal.

I do hope that your boat is rated for at least 70HP.

Good luck.

 

[1kruzer1]

Re: Considering buying a 77 Johnson 70HP motor please help.

Sorry to contradict JB, but the '72 50 horse is electric shift, and the '77 70 horse is mechanical shift, so the controls are completely different. You'll need to find a control assembly with both Throttle and shift cables, 1976 or later, but many model years will work with this motor. I believe there is a good chance the transom bracket dimensions are identical, so the motor will likely bolt right into the identical place without having to drill new holes, etc. Not sure about adding power trim and tilt, as I have never taken on that project. With clean carbs and proper tuning and prop these motors are remarkably fuel efficient, especially considering the vintage. Good luck.

 

[fireman57]

Re: Considering buying a 77 Johnson 70HP motor please help.

The tilt and trim are hard to find without spending some big $$. I got lucky and found a pristine unit online for 250.00 and then the wiring and relay box with switch for another 125.00. If you look at new aftermarket you are looking at around 15-1700.00.
I am currently working on a 1978 70hp that has me befuddled. I did a search on this forum on this engine and it seems that from '76-about '79 or '80 they had hesitation issues and lean running issues. do a search on here for 1977 70hp and read the threads. I know that others will say these are great engines but I have become suspect of these model years for this horsepower. I do like the engine and it is strong as an ox when running right but this issue seems to be a common thread when you read the posts. That being said I am not an OMC mechanic or anything of the sort. Just been working on them for myself and others for about 20 years on the side. There is a ton of valuable info on this site so take your time and read all about that engine here.

 

[JB]

Re: Considering buying a 77 Johnson 70HP motor please help.

Sorry to contradict JB, but the '72 50 horse is electric shift, and the '77 70 horse is mechanical shift, so the controls are completely different

Thanks for the correction, kruzer.

 

[mattzmojo]

Re: Considering buying a 77 Johnson 70HP motor please help.

Thanks to everyone. I will take my time and see what I can find that comes with t&t. It kind of becomes a pain in the butt after a while raising and lowering the motor when I have to go in and out of certain parts of the river I go out of.

I think these older evinrudes/johnsons are a fantastic pieces of engineering. They seem to run like tops with the proper maintenance and TLC.

 

[fireman57]

Re: Considering buying a 77 Johnson 70HP motor please help.

To be fair about my experience with this engine there were two problems that actually masked each other. It is fixed now and runs like a dream. I am still leery about '76-'80 models in this horsepower range.

 

[BonairII]

Re: Considering buying a 77 Johnson 70HP motor please help.

To be fair about my experience with this engine there were two problems that actually masked each other. It is fixed now and runs like a dream. I am still leery about '76-'80 models in this horsepower range.

What were the 2 problems?

(I own a '77 75 Evinrude)

 

[fireman57]

Re: Considering buying a 77 Johnson 70HP motor please help.

had an air leak on one gas tank and the powerpack would drop a cylinder after running WFO for about 20-30 seconds on plane. You could stop and idle for a minute or so and it would take off and run good again for 20-30 seconds. Acted like it was running out of fuel. Got the air leak stopped and it still did the same thing but I could see plenty of gas going into the carbs. Gotthe old timing light out and would lose spark on number one. swapped coils and still lost spark on number one so am replacing the powerpack. Should be good to go then.