1979 johnson 70 hp back to life advice with Jet lower unit

[fishjumped]

No place to hook up garden hose for trailer starting I just bought this project it has not run since 2003 i was told. So far I have drained the stale gas from the tank and have put fresh gas into the motor from another source and it has been in the carbs for a couple of days to possibly help dissolve whatever sediment may have collected in the carb bowls.. as a first try to avoid removing the carbs. any advice on if a flushing technique like this would work?

secondly It is a jet drive and I need to drill it to accomidate a garden hose fitting. so I am going to attempt to start this motor without water for a few seconds worst thing it could do is overheat the powerhead however I am going to shut it down before that would happen. the inpeller has to be replaced anyway. from age and to drill it I need to remove the jet drive. as for the impeller it is going to be sacrificial in this case so could there be any precautions to take considering what i am going to do? Please advise..Scott

 

[Mntom]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

Far as the carbs, I would rather pull them and clean them instead of hoping they are. Cleaning and going through the carbs will probably be less labor too since you will probably wind up cleaning them anyhow.
I don't have any experience with jet drives, so I can't say one way or another about drilling for a hose. There is not any way to put muffs on it?

 

[Outsider]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

Unlikely you can supply the volume of water thru a tapped fitting that would be required to flush the powerhead. Impellers are usually 'shimmed' to proper tolerance, and aren't really sacrificial. I used one in Alaska glacial rivers for 3 years (about the most abrasive condition there is), and added a single shim one time. Before doing carbs, I'd try a "Dunk" treatment ...

 

[fishjumped]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

ohh not the jet drive impeller the Waterpump impeller for eng cooling.

 

[Bass_boy7]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

why don't you jsut drop it in a bucket of water a big rain barrel and fire it up?

 

[Sixmark]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

ohh not the jet drive impeller the Waterpump impeller for eng cooling.

Oh sure go ahead, they made those with the intention of running them dry, they had nothing better to do than waste some extra rubber.

So, when you come back on the forum a few weeks from now asking why your motor overheats all the time, then you will have your own answer "because I ran it dry and now a piece of the impeller is blocking a water passage".

You can probably plan on replacing the water pump housing or the cup and plate after your little experiment.


Your motor, your money

 

[fishjumped]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

Oh sure go ahead, they made those with the intention of running them dry, they had nothing better to do than waste some extra rubber.

So, when you come back on the forum a few weeks from now asking why your motor overheats all the time, then you will have your own answer "because I ran it dry and now a piece of the impeller is blocking a water passage".

You can probably plan on replacing the water pump housing or the cup and plate after your little experiment.


Your motor, your money

hey I was seeking advice... do you have Jet drive experiance if so talk to me brother Im here for information and guidence. soI guess it would be better that I make the accomidations for the garden hose or go to the lake and back it in and try to fire it up, Now I am not sure a motor sitting for 7 years would just fire up. so here i am in a pickle. looking for some help so far not much.

 

[Sixmark]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

Ok if you want to know where to start:

Don't connect a fuel source to it, pull the spark plugs but be sure to ground the wires to avoid damaging the ignition components

With that done, have someone turn over the motor while you do a compression test on each cylinder, compression should be within 10% of each other on all cylinders, if you have one that is drastically different then you have an issue.

While you were doing the compression test you may have noticed if you had spark to each plug wire, if not you can throw the plugs back in and hook up the wires, again have someone spin it over while you use a timing light to check for spark, or you can pull the wires off one at a time and hold it about 7/16 to a 1/2 inch away from the end of the spark plug (use a good insulated pair of pliers for this method) if you get a good spark jump then continue to the next wire.

Now you have discovered if you have good compression and spark or if you don't......if you do then continue on

You mentioned the impeller, at this point I would recommend installing a new one before you go further, also change out the lower unit grease, the method on your jet conversion should be similar to a standard lower unit.

CHeck out your fuel lines and make sure they are in good shape, if it's questionable then replace it. Hook up your gas tank to the motor and pump the fuel bulb, look for any fuel leaks, Charge the battery and take it to the local lake, but try to go during low traffic times at the landing, if you know of a place you can drop it in without being in the way of others then do that.

Now make sure the kill switch lanyard is in place, and try starting the motor, it may take some playing around with the idle lever, fuel bulb and choke to get her to fire after so long.

That should be enough to keep you busy for awhile, you will probably have to remove the carbs and clean them out, however every now and then someone gets extremely lucky. See how things go after these steps and let us know what happened. FYI, if you hear a buzzing sound coming from the control box then shut it down, that would be your overheat alarm

 

[d.boat]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

I have owned an outboard jet for many years. They are all made by the same company so, first, look to outboardjets.com for faq's owner's manuals, etc.

My advice to OP: THERE IS NO REASON TO RUN IT DRY. Just add the flush fitting. Assuming it's possible, it will be a simple 20 minute job to drill and tap it, or if you don't know how to tap, just bring L/U to any mechanic shop and put an X on the spot and tell them the diameter of the hole and thread spec. A $20 job. Removing the L/U is as simple as removing a prop L/U.

A garden hose provides plenty of water for the water pump and jet impeller at normal "hose" RPM's (high idle, for example).

To make sure it can be added to your older unit that does not have one. Go to the website and find the model number for your year and HP. Then, find the owner's manual for that model, and see if the parts diagram has parts for a flush fitting. If it does, it can be added to yours. I believe the website will have clear instructions, if not, call the company and they'll email or fax (they've been very helpful to me in the past). It won't be difficult - it's just a simple hole drilled and tapped, but check first to see if it is possible on your unit (my guess is yes).

As for running it in a bucket or barrel as someone mentioned - not possible. The outboard jet drive's propulsion impeller is spinning all the time, there is no "neutral" (neutral and reverse are achieved by positioning of the reverse gate ). Therefore, all the water would be expelled from the barrel within seconds. The only ways to safely run are to put it in the water or get a hose fitting.

 

[fishjumped]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

Thank you for being clear on this and thats my Plan R&R the lower unit and while it is out drill and tap the manual says 3/8 16 thread 11/16 " FROM MATING FLANGE THEY SELL THE HOSE ADAPTER I presume .. so wouldn't the Waterpump impeller been damaged if I did a compression test without water to the cooling system? it may be too late I fired it up for the first time it ran about 15 seconds before quitting so Carb work to be performed.

 

[Sixmark]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

Thank you for being clear on this and thats my Plan R&R the lower unit and while it is out drill and tap the manual says 3/8 16 thread 11/16 " FROM MATING FLANGE THEY SELL THE HOSE ADAPTER I presume .. so wouldn't the Waterpump impeller been damaged if I did a compression test without water to the cooling system? it may be too late I fired it up for the first time it ran about 15 seconds before quitting so Carb work to be performed.

doing a compression check only requires a few revolutions of the motor, actually running the motor for even 15 seconds is about 150 revolutions, the last thing you want is to suck up chunks of impeller into a water jacket and have it get lodged, it could prove very costly later.

 

[fishjumped]

Re: 1979 johnson 70 hp back to life advice with Jet lower unit

thanks fo all your guidence and help I now have a smooth running Engine in tune .. the carbs came off and rebuilt water circulation through the cooling circut with hose adapter great stream through the tell tail. great compression 140 138 and 137 started right up and warmed at fast idle 1500 RPM a couple min then down to 800 RPM steady idle a few bumps of the throttle and great responce no lag again thanks for all the help

Fishjumped