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'72 Evinrude Sportwin bogs down and quits

CarMech1969

CarMech1969

Regular Contributor
Hello all,
I'm back here again, hoping to obtain some advice.
My '72, which I recently acquired, has developed a strange sort of problem.
What happens is, if I run the motor at WOT for an extended period, after a given time, the motor will start to decelerate on it's own, lose power, and finally cut out.
It doesn't seem to do this on lower throttle openings, however.
If I immediately pull the cover after a high-speed run, a bit of smoke can be seen rising off the cylinder head. Overheating perhaps?
During a high speed run, just prior to it quitting, the water peeing out seems to reduce in volume.
The engine will start and run fine again if it's left to cool down awhile.
A friend of mine had a Mercury 7.5 with the exact same symptoms, but I forget what the fix was.
Anyhow, I pulled the water pump and everything looks OK. The impeller feels soft and pliable, with no signs of cracking.
Pulled out the thermostat, and it appeared as though water had been circulating.
If you guys could suggest as to what to do next, I would be very thankful for it.
Happy boating, mates! :cool:
 
Disregard the following as I've been told you have a small hp engine. I'm leaving the following as it may help some other members with a similar problem with a higher hp model.

You didn't list what horsepower that engine is but I'm taking a guess that it may be a 1972 3 cylinder, V4 or possibly a 2 cylinder high hp model and have worded my reply as such so as not to waste time should I be lucky enough to guess right.

You're describing a engine that is overheating to an extent that it is seizing up to a point whereas the pistons are being crushed by the overheated collapsing cylinder walls. Yea, I bet you saw a bit of smoke rising off the cylinder heads.

Either that engine is sitting too high on the transom, the water pump is failing (too flexible), or the water deflectors which are visible in the crankcase water passage when the heads are off are swelled and restricting the water flow.

That engine has a warning horn system that sounds when the engine reaches a temperature approaching the overheating point and sound off with a constant steady blast before any damage is done. Test the horn by (engine not running) having the key in the RUN position, then ground out the TAN wire you see protruding from the cylinder heads. With that wire grounded, the horn should sound... if it does not, find out why as that the only warning you'll receive before the engine seizes up.

At a minimum before you run the engine again, do this............ Torque the cylinder head bolts to 18 to 20 foot pounds in the following sequence as they are surely loose tight now.

9....10
5.....6
1.....2
4.....3
8.....7
 
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Hey Joe, thanks for your reply.
I forgot to say that it is a 9.5 HP. Do those have an overheat warning horn?
The water pump being too soft could be it, the rubber felt more pliable than other impellers I have checked out.
Oh yeah, another thing. There was some sort of oily frothy buildup on the outside of the water pump cover that I noticed when I first pulled the LU down.
Is that anything to be concerned about?
Thanks for all your help.
 
racerone said:
I thought the " sportwin" was the 9.5 HP model.----No warning system or electric start on that model.
Click to expand...

You're correct of course. I didn't bother to look at the name designation. If the horsepower or model number doesn't jump out at me... my mind blocks the rest... sport twin, big twin, starflite, whatever.

If what he has is indeed a 9.5 hp, don't play with it... replace the water pump complete along with the thermostat. And torque the cylinder head 96 to 120 INCH pounds in the following sequence.

9....10
5.....6
1.....2
4.....3
8.....7
 
Ah ok, thanks racerone.
The last time I ran the motor prior to today was around a month ago.
It was perfectly fine when I had used it last.
What could cause the impeller to go soft? Could dumping fuel on it mess it up? Because i think I might have done that a couple of times. Just speculating.
Thanks again!
 
The reason why i say fuel is because a few times, I drained the carb without bothering to catch the fuel with anything. I just let the fuel dump out. Would that damage the impeller? If it does, I'll stop that habit and soak up the fuel with a rag. Appreciate all the help.
 
Could a weak fuel pump or low float level also cause overheating? I'm not well experienced with 2 strokes, any feedback is appreciated.
 
CarMech1969 said:
Could a weak fuel pump or low float level also cause overheating? I'm not well experienced with 2 strokes, any feedback is appreciated.
Click to expand...

Nope.... It would need to be related to a blown head gasket, weak water pump, stuck faulty thermostat... something of that nature.

Also... if you're attempting to use a short shaft engine on a long shaft boat, that'll do it too. The cavitation plate just above the prop should be approximately 3/4" below the keep at the transom.
 
joereeves said:
Nope.... It would need to be related to a blown head gasket, weak water pump, stuck faulty thermostat... something of that nature.
Click to expand...

What should I see if I pull the cylinder head? Does the 9.5 have water deflectors? I'm guessing not. My manual has no clear pics, or at least couldn't find them.

It's a 143 degree thermostat, and I tested it in a small pot of water and a thermometer. It just starts to crack open a bit at 143 or so.

I tried running some water from a garden hose through the thermostat opening in the engine, and no debris or unusual build-up of anything was in there. Tried the same thing with the LU. All clear.

Guess I will try a new thermostat and water pump and see what happens.

Will keep you posted...

joereeves said:
Also... if you're attempting to use a short shaft engine on a long shaft boat, that'll do it too. The cavitation plate just above the prop should be approximately 3/4" below the keep at the transom.
Click to expand...

The boat is a 12 foot aluminum. I ran my '64 Evinrude Sportwin 9.5 on it with no issues. So I don't think that's it.
 
joereeves said:
Apparently the shaft length is fine. There are no water deflectors in that model.
Click to expand...

Thanks Joe! One other thing. When I flushed the powerhead from the thermostat hole, water came out from the copper tube which leads to the water pump, but it also came out from somewhere else on the powerhead, but I was unable to see from where when looking around with a flashlight. Does this mean that I have leaky seals or gaskets in there somewhere? I was thinking perhaps this could be the reason why I having this weird problem?
Appreciate all the help so far!!
 
CarMech1969 said:
Thanks Joe! One other thing. When I flushed the powerhead from the thermostat hole, water came out from the copper tube which leads to the water pump, but it also came out from somewhere else on the powerhead!
Click to expand...

Water flows up the water tube and to the thermostat area of course, then it flows throughout the cooling system and exits the powerhead at a point to shoot down the long exhaust housing that exists between the powerhead and the lower unit (this is the somewhere else that you cannot see with a flashlight). If not for this feature, the exhaust housing would get so hot that the paint would burn off.

Another water exit point is naturally the telltale exhaust/water outlet via the rubber hose/tube at the rear of the powerhead.

I assume you haven't installed a new thermostat and water pump assembly yet?

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
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Not yet, but I intend to.
When I went to my local NAPA to nab some parts, they were telling me that there is nothing available in the warehouse, and that it would be a 3 week wait for parts if I ordered them.
Forget that. I'd like to put together a parts list, and order everything one time, so that way I'm not going back and forth, and I could perhaps save a bit on the shipping, too.
Guess that's what we get for living in Canada....
I didn't think it was that much of a barren wasteland up here.
Hahahahahaha!
 
Your WOT slow down slowly. Suree sounds like a heat problem with the head gasket slowly opening up. The steamy / smokey head is / should be Joes diagnosis of the problem.

Question WHY is this problem now occuring ? The super soft impellor blade could be the cause of so much cylinder scuffing now.
 
cyclops2 said:
Your WOT slow down slowly. Suree sounds like a heat problem with the head gasket slowly opening up. The steamy / smokey head is / should be Joes diagnosis of the problem.

Question WHY is this problem now occuring ? The super soft impellor blade could be the cause of so much cylinder scuffing now.
Click to expand...

Funny you mention that.
When I checked the torque of the head bolts, they were really loose, just like Joe said.

When the engine quit, it would not start again until it was allowed to cool down for a while.
A friend of mine had the exact same problem with his Mercury 7.5, it would get hot, bog down and quit.
He is NOT mechanically inclined at all, he took it to a shop, I even remember looking at the work order, but can't for the life of me remember what the fix was. But it wasn't anything all that major to get it going again.
I'm thinking to order an impeller, a t-stat and a head gasket.
Is there anything else that I should try or look at before I order the parts?
Again, thanks very much to everyone that helped.
 
CarMech1969 said:
Is there anything else that I should try or look at before I order the parts?
Click to expand...
Was hoping that someone here might answer the question.
I mean, what the hell. There's no rush. I got my '64.
That said, might it be a good idea to remove the cylinder head, and inspect the cylinder walls?
 
CarMech1969 said:
Not yet, but I intend to.
When I went to my local NAPA to nab some parts, they were telling me that there is nothing available in the warehouse, and that it would be a 3 week wait for parts if I ordered them.
Forget that. I'd like to put together a parts list, and order everything one time, so that way I'm not going back and forth, and I could perhaps save a bit on the shipping, too.
Guess that's what we get for living in Canada....
I didn't think it was that much of a barren wasteland up here.
Hahahahahaha!
Click to expand...

It's not. Any Johnson/Evinrude shop can get you the parts. I can get pretty much anything from my local shop for my old motors, never found anything yet I couldn't get. That's including for my 1958 collection!! Parts are usually in within a week.
 
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Time to do a little bit of searching in the GTA area.------More than one shop that will help you.------Just be ready with some cash.
 
I found the easiest way to get parts is to pull up the parts diagrams on this site, and take the part numbers with me to the shop. Saves them having to look into old parts books, or the computer, to find whatever it is you need. Most of the wear parts are available from Sierra, some are BRP only. BRP has done a GREAT job of preserving the availability of old OMC parts, such as gaskets, etc.
 
Does it run properly with the cover removed???...exhaust leaks are common on these motors and can cause problems. If it runs ok with the cover off, look for an exhaust leak.
 
bobbyc said:
Does it run properly with the cover removed???...exhaust leaks are common on these motors and can cause problems. If it runs ok with the cover off, look for an exhaust leak.
Click to expand...

At this point, it seems to be an overheating issue....just came out of the blue...was working perfectly when I stuck it in the garage a month ago.
Please see my original post for a little more insight.
 
Hello mates,

I'm back again after doing some work on my 1972 Evinrude Sportwin 9.5.
Got a new water pump and thermostat into it, and I replaced the fuel pump as well (the old one had rust in it).
Got the head bolts retorqued as they were loose.
The motor starts easily and runs great, but I am still experiencing problems.
After a few minutes, the motor starts bogging like it is misfiring, and then quits.
I tried putting my hand on the head for a slow count of six, but it was too hot to do that.
I have water coming out the pee hole, so I am now at a loss.
Any further ideas would be extremely helpful.
Thanks in advance all, and enjoy the rest of the day!

Regards,
CarMech1969
 
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