1978 Johnson 70hp

[martanga2]

Any one had this problem: Motor starts no probs and idles, after a while (20-30 seconds) when giving it revs it just dies and when turned over straight away motor is tight like seized, but 5 seconds later starts and idles. Anyone know or experienced this problem?
Motor hasnt been running for 9 months as just replaced power pack.

[FNQCairns]

More information, are you giving the engine revs in gear on the boat or on the muffs, did you try and turn the flywheel or is it siezed via starter motor only. You are running oil in the fuel? and is there water pumping? How hot is the engine ie too hot ot touch for 3 seconds or still cool.

There are reasons for lockups but to narrow the field need to know whatever else you can think of.

cheers fnq

[Noelm]

as mentioned we will need you to do some very basic troubleshooting, so first off, being a 1978 model it will be a "mix your own" so did you put Oil in the Petrol? if your estimation of time running is pretty close, then I doubt that you have a cooling problem (yet) as even with no water at all, it will go for longer than 30 seconds (well it should) but to be sure, feel the motor after running and see if it is very hot to touch, I don't think that that model had a "tell tale" so you would not know if it was pumping water for a while, when it warms up there will be some water coming from the upper squareish holes below the cowling and on the rear of the leg.

[FNQCairns]

Yeah Neolm thats my thoughts also too fast for a heat related lockup in neutral, on the water after warming it up a bit the giving it some in gear it might be possible.

If the bloke comes back will be interesting to hear whats up, hydraulic lock even?

cheers fnq

[Noelm]

yes, we will see what he comes back with, if it is a no Oil problem, it should be OK on one of those old "clangers" i have seen them seized solid and still chug on for years after Oil is added, so lets hope!

[martanga2]

I've always had muffs on while starting, tried both in gear and out of gear. just started again for a test from cold, had on high idle from start and lasted 2 mins was quite hot on the head. Just had a brain wave, could it be the thermostat? i Dont know much about outboards so hopefully im wording it alright.

[Noelm]

yes it COULD be the thermostat, but more than likely not, do you have oil in the Petrol?? if yes, then good, and 2 minutes does now seem like an overheat problem, by quite hot, do you mean you cannot keep your hand on the Motor? or just a bit hotish? after a bit of running, do you see anywater coming from the vent/exhaust holes on the back of the leg, just below the powerhead area? if it has not been used for Months, it would more than likely be the water pump just frazzled when it was started, a fairly easy and cheap job to do your self if you are a bit mechanically minded.

[FNQCairns]

Yeah sounds like 0 water circulation and/or no oil in fuel, not even a cold seize fits the symptoms well.

cheers fnq

[martanga2]

I've got oil in the petrol 50:1. and all water is coming out of holes where it should be.

[Noelm]

OK then, we have oil, check, we have water, check, so now we must work out whether it seizes when put into gear (gearbox?) or actually seizing up, from over heat, (in neutral) when it does stall/seize, have you tried to turn the flywheel by hand to see if it is jammed? we need to know that next, and while you are at it, get a much better idea of how hot it is, hot enough to seize is HOT not warm, and from then we can sort out possible causes.

[Noelm]

what I am getting at, the gearbox may have no oil or full of water or something and jamming up when in gear, we need to see if it is still doing it in neutral, it is not all that likely, but best eliminate all easy stuff first!

[martanga2]

I got home today and took thermostat cover off, it was fill of salt and sand, scraped it out and cleaned, put it back together and now running fine over 20 minutes, gonna put boat out in the bay and give it a tester (no worries auxillary is all good). I booked it in for next week to get head taken off and all cleaned, will post to let you know how it goes this evening.

[martanga2]

Took it out for a cruise, went ok but droping revs, didnt die out though so i think take the head off andgive it a good clean out might do the trick.

[Noelm]

kind of thinking if you could remove the Thermostat yourself, then the Head removal will be within your capabilities, but beware of breaking bolts! but if you do not feel confident, then by all means take it to a Mechanic to have it done. did you by chance feel the Motor after you had it running to feel how hot it was??

[martanga2]

yes did remove the thermostat, will definately take to mechanic as i dont want to risk any damage. the motor was very hot to touch before i cleaned under therm cover, When i took out on the water temperature had dropped hugely.

[martanga2]

Verdict: there is a crack right down the casing of middle cylinder,rip, will have to go shopping for another motor.

[FNQCairns]

Thats no good, shame it was not a simple replacement fix of some part, does sound to me the seizures you experienced was infact hydraulic lock related.

Good luck with your next engine and consider gettingit checked over well, can be worth the extra payout sometimes.

cheers fnq