Johnson 70 hp analysis & prognosis ??

[Peter O]

I took my just purchased '96 Johnson 70hp oil injected for my first run on Saturday. I had it inspected before I bought it and it was just about perfect. I had it tuned up on Friday with new plugs. Compression was 145, 140, 145. <br /> I warmed it up at 1500 - 2000 rpm for a few minutes and then was cruising at 4000 rpm for about 20 minutes. I increased the throttle to 5000 rpms and shortly after the motor started to "rattle and knock". (Bang is too strong a word). I immediately slowed down and put it into neutral. The motor stalled. I was able to start it twice but as soon as I put it into forward gear it stalled. I attempted to start it about 10 more times. The motor would turn over but not catch. Eventually, the motor would not turn over and I just get a single click. The battery has lots of juice in it.<br /><br />Opinions please on what the knocking might be. Also, why won't it turn over any more?<br /><br />I have taken the motor to a mechanic but he can't look at it until late this week or early next. I know this is a little long but I am sick at the thought of what it might be.

 

[hondon]

Re: Johnson 70 hp analysis & prognosis ??

First step would be to pull the plugs and see if you have any unusual deposits on them.Then take a good look at the # on the plugs.This engine requires that you use supressor plugs and if you are not it can make you go into false SLOW which it sounds like may be happening to you.Look for Champions starting with a Q or NGK with a Z somewhere in there.Also how hot are you getting? Perhaps this not false overheat warning and you really are overheating.Do your warning horns work?With all that cranking it is possible that you have cooked the starter, but clean ALL connections associated with it, and see what happens.Finally ,if the plugs look good and you get it cranking ,or trying to crank again,and still some trouble,pull down the gearcase and se if that helps.

 

[Peter O]

Re: Johnson 70 hp analysis & prognosis ??

Thanks Hondon. The plugs are correct for the motor. What's a false slow? I only slowed when I put the motor in neutral. Also, there was no overheat warning or overheating for that matter. I didn't crank the bejeepers out of it but may have damaged the starter. Any ideas on the rattling / knocking sound? What would the purpose of pulling down the gearcase be? Anyone else have an opinion?<br /><br />thanks

 

[fireman 757]

Re: Johnson 70 hp analysis & prognosis ??

Are you sure that your oil injection is working properly? Sounds like a mixture problem. Possibly too lean and your cylinders arenot getting lubed properly. that could possibly start your knocking. Once they got so hot they would start to seize and your engine will not start. Not saying this is it. Just an opinion. Anyone else??????

 

[Joe Reeves]

Re: Johnson 70 hp analysis & prognosis ??

Peter.... You use the words "Just Purchased" and "First Run", then you say that you encountered a banging/knocking noise on that first run. A noise of that type is not normal, and the fact that the engine simply clicks now (with a good battery) when you attempt to crank the engine indicates that the starter solenoid is engaging, the starter bendix is engaging the flywheel teeth, but the engine is jammed.<br /><br />This jamming could be due to a powerhead failure or a lower unit failure (the two being connected by a driveshaft).<br /><br />My advice would be not to touch it, but to take it back to wherever you purchased it to have it taken care of under warranty. However, if your receipt has the words "As Is" imprinted or writen upon it... that's bad news!<br /><br />Let us know what happens with this problem.

 

[Dhadley]

Re: Johnson 70 hp analysis & prognosis ??

You said the plugs are correct for the motor. What are you using? What fuel? What water pressure?<br /><br />These motors tend to run lean in the mid range (where you were running) and tend to lean out the middle cylinder. <br /><br />Let us know what you find.<br /><br />Good luck!

 

[Peter O]

Re: Johnson 70 hp analysis & prognosis ??

Well folks, thanks for your input. I think Joe Reeves wins the prize for diagnostics. I got the call today and the powerhead is toast. Unfortunately I bought the boat privately and there is no warranty. I DID have the motor checked out before I bought it and everything was fine. The marina told me they did not think the seller knew there was any problem as the compression et al checked out. Just my very bad luck. I don't think I will have it rebuilt as I can buy a new Merc 75 for about $7500 (cdn) and the estimate for the rebuild is $4000 and half of our very short summer. Just goes to prove there are no guarantees in life!!

 

[Dhadley]

Re: Johnson 70 hp analysis & prognosis ??

Is it number two (middle) cylinder? If so there are some things to do to prevent a repeat. I think 4 grand is a tad high if the crank is good and the block is boreable. <br /><br />Take a look at my earlier post and get back to us with specifics. There may be other routes to take.<br /><br />Good luck!

 

[my new fishmaster]

Re: Johnson 70 hp analysis & prognosis ??

If you had purchased a new Honda you would not be having this conversation.

 

[Dhadley]

Re: Johnson 70 hp analysis & prognosis ??

Easy on the bashing! Lets all play nice! <br /><br />Really!

 

[dtro]

Re: Johnson 70 hp analysis & prognosis ??

I would suggest that you look around at prices. I was able to find a mechanic to do it "in his spare time" for 1500. Parts and labor. Sure beats 7500 for a new one and chances are during rebuild you can find what went wrong and prevent it in the future and to give you a longer life of the engine. In my case it was the injection system, which I no longer use.<br />Of course I am speaking US $, and not sure of the present exchange rate....but still seems high.<br />Oh, and by the way mine fried the same way' third time out, so I feel your pain. <br />I'm glad I have an understanding wife.

 

[DJ]

Re: Johnson 70 hp analysis & prognosis ??

peterO,<br /><br />Don't forget to check this site for good engine deals. <br /><br />Fishmaster, that was a VERY CHEAP SHOT.<br /><br />After what I've been through with Honda Marine, I'll NEVER buy one.

 

[fireman 757]

Re: Johnson 70 hp analysis & prognosis ??

Sounds like you're going to buy a new one anyway. Keep your old one and try to rebuild it yourself. It's not as hard as you think it is if you take your time. It's broke anyway right? At least you would be able to sell it. NEVER trust oil injection. It doesn't take any more time to mix it yourself and you know it is right.

 

[Peter O]

Re: Johnson 70 hp analysis & prognosis ??

Thanks for the advice. I've decided to go with a 75 hp Yamaha 2 stroke. It's actually about $800 cheaper than the Merc. 80lbs lighter, 2yr warranty vs. 1 yr. on the Merc. Aside from that, the real deciding factor was the result of my search on this board for Yamaha vs. Merc. experience. I expect I will only put no more 60 hours a year on the thing so I should be able to pass it on to my as yet unborn grandkids!! I will consider trying to rebuild the Johnson this winter but not really sure I can do it. I am not too knowledgeable about motors and mechanics.

 

[FlyBoyMark]

Re: Johnson 70 hp analysis & prognosis ??

Peter, Give Tohatsu/Nissan a shot IF you have a dealer near you. Very nice and reliable outboards that come with prop, combo tach, and control for 20% off of list on their web site.<br />Very light weight too.....2 year warranty on 2 cycles.... Should cost you $4,661.00 plus tax us dollars.