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Any one else have this problem


Rafinx

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Hey guys not after cheap ways of fixing my engine or anything.

I used to be a apprentice mechanic for automotive for 2 odd years, I dont live swapping fields, but try to when I can to save money. But I cannot determine the issue as of yet.

My motor is a 1974 35hp evinrude, now, it used to run just fine when i bought it, start first go everything.

Anyways I decided to change the spark plugs because the old ones started to look abit gluggy.

unfortunately I didnt get to drive it for awhile. I got the chance to drive it one day and as soon as it heated up it decided to just die and go no faster than idle speed.

Thinking critically i figured i would take it out of gear and rev it, to take load off. Sure enough the engine rev's when up normally.

I wanted to ask if changing the heat rating on the spark plug could do something along those lines?

I was thinking of changing them again anyways, but maybe there might be another play in it, as I made sure there was no air in the fuel line etc.

Any help will be appreciated.

Edited by Rafinx
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Hey guys not after cheap ways of fixing my engine or anything.

I used to be a apprentice mechanic for 2 odd years, but cant determine the issue as of yet.

My motor is a 1974 35hp evinrude, now, it used to run just fine when i bought it, start first go everything.

Anyways I decided to change the spark plugs because the old ones started to look abit gluggy.

unfortunately I didnt get to drive it for awhile. I got the chance to drive it one day and as soon as it heated up it decided to just die and go no faster than idle speed.

Thinking critically i figured i would take it out of gear and rev it, to take load off. Sure enough the engine rev's when up normally.

I wanted to ask if changing the heat rating on the spark plug could do something along those lines?

I was thinking of changing them again anyways, but maybe there might be another play in it, as I made sure there was no air in the fuel line etc.

Any help will be appreciated.

Hi, what spark plugs are you fitting and I would service the carby due to blockages in the main fuel jet, that under load will not let the engine rev. Of course could be many other things and you want to make sure you have the basics like compression, fuel, spark and air and the engine is not overheating and yes to answer your question I have seen many engines of all brands and ages act like this, but 9 times of 10 it is a simple fix if you know what you are doing.

Cheers,

Huey.

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Sounds fuel related.

More then likely the spark plug replacement and the issue you now have sound to me unrelated.

Should you wish to rule the plugs out in your own mind you could purchase some new plugs in the correct heat range? Common plug 4 to $5 each retail?

The engine is not mis firing and breaking down under load?

The fuel is fresh?

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unfortunately its been a lil bit since ive seen my boat as i leave it at my dads factory, as theres no room here, Yeah see idiot me did not keep the original plugs, and I looked up on the net for the matching brand from ngk to bosch. So may be it. As for the carby clogging, I cant see how it happens due to the fact it will rev normally under load untill its been running for about 5-15 minutes. The fresh fuel is a new one, I should go have a look see about that, if not ill just cover basics. See my dad did tell me he has had a similar issue with a boat he used to own back in the day, about air in the fuel line, and that was what was causing it to be in my situation, sure enough he was right I pressed the bulb and noticed abit of air, but a couple of worm clamps fixed it compared to crimpping clamps.

Ill try to go get the spark plug type in a couple days, not now as Ive got uni exams to conquer.

Thanks guys the helps appreciated.

oh If any one is interested ive got photos of the restoration work of the trailer It was a complete overhaul of springs, hubs, brackets, axle etc. Might come in handy if any one needs any hints to go about it, Im just waiting for the wheel arches to go on and then bang my $900 boat is back on the water. :)

The boat will be going for a server closer to the warmer months when Ill be able to move it, till then I just start it for about 15 minutes every 3-4 weeks.

Edited by Rafinx
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I had this problem a month ago ( although I hadn't changed the plugs). Check for water in your fuel, it seemed to be the culprit in my case. I think it blocks the injectors in the carby as it's more dense than fuel but I'm no mechanic.

Just a thought

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There are quite a few suggestions here , all worth checking.

A friend of mine had a 35hp Evinrude with the same problem.

When first started , ie motor cold , will it rev out normally in gear then , after a few minuits , when the motor is at operating temp , drop back to idle.

If so , suggest it is the heat sensor located in the block.

Check with Huey , for testing purposes , there is a way to bypass the sensor.

I dought it is the plugs , it's just coinsidential the problem has occured with the plug change

Geoff

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Very strange never seen it in cars.

Thats because cars have a temp gauge attached to the heat sensor to alert the driver of a problem.

Some outboards , in particular early models do not have a temp gauge as such so to prevent the motor from overheating a heat sensor controls the motor automatically

Geoff

Edited by Geoff
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Does it ever cut the motor off?

I ask cause my outboard has no temp gauge either, which worries me all the time! I keep putting my hand behind the cowl where the gap is too feel how hot it is.

I've not experienced a total cut out. Perhaps that was due to the sensor being faulty , not that the water pump had failed & there was no water going through the motor.

Huey would be the best one to advise on the cut off question

Geoff.

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Does it ever cut the motor off?

I ask cause my outboard has no temp gauge either, which worries me all the time! I keep putting my hand behind the cowl where the gap is too feel how hot it is.

If your out board has no temp gauge, the easiest way to monitor engine temp is via the coolant. Just stick your hand in the coolant stream. You become the temp gauge

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Nah it has not ever cut off, but funnyly enough you made me remember that it cut back in after a little bit it would jump in between working properly and going back to idle speed, but when it happened it was variable.

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  • 1 month later...

Just wanted to reignite this issue, as Ive found a tad more information.

I took the boat out on friday to try out the new fuel and larger fuel line. Unfortunately it did not fix the problem, What I did find tho is once it got to the that temp that makes it slower, I noticed that when I slowed it down completely it just died out and would start untill it cooled down. Now This only happens when I am not going full ball down the river system as I take speed limits seriously.

Anyways what I am thinking it is, is that there may be a blockage of some sort in the motor stopping it from cooling down completely. Hence it puts itself in a fail safe mode?

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Showing my ignorance here, but do outboards have a thermostat that restricts coolant flow to make it warm up faster?

If a thermostat isn't opening and closing up properly it will mess up the heating and cooling abilities.

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funny u should say that, the guy i bought it off removed the thermostat completely lol.

Straying off the topic I know but, me & my mate have had this argument before, his thermostat was RS & new one was incredibly pricey(compared to automotive) , about $50, so he thought I'll just chop the middle out & run without, engine runs fine but they are designed to get the motor up to the ideal running temperature quicker & me thinks these big companies who spend serious $$$$$$$ on research & development wouldn't put it in there if it didn't need it for the benefit of the motor in the long run. just my midday rant !!

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Straying off the topic I know but, me & my mate have had this argument before, his thermostat was RS & new one was incredibly pricey(compared to automotive) , about $50, so he thought I'll just chop the middle out & run without, engine runs fine but they are designed to get the motor up to the ideal running temperature quicker & me thinks these big companies who spend serious $$$$$$$ on research & development wouldn't put it in there if it didn't need it for the benefit of the motor in the long run. just my midday rant !!

I've also got the 35 Evinrude, (later model)

Sounds like the o/h sensor to me.

Designed to protect if your impeller starts to die, or (in my case) you pick up a plastic bag or weed which blocks the water intake.

Buzzer sounds, and power is cut right back. Usually shows as steaming from the tell tale, as well.

In my case, once the bag removed, and the motor cooled down, needed to switch off and wait for a bit until the system reset. Then fine.

If you are not showing any cause, maybe the sensor is faulty, and causing a false shut down?

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Hi Rafinx,

Is your ignitions system electronic or points system ?

My 1971 20hp had the same problem, Initally from cold would get up & plane then once warm die to an

idle.

My 20hp is old school my issue was caused by a faulty condensor.

Hope this helps.

Cheers

Zed.

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ARGH this is driving me crazy, you both have valid faults, And ive just left my boat for the day, I will be going back tomorrow.

I checked the carby butterflies they are clean as a whistle, could not believe how clean it was. Im also thinking of checking if I have oil fouled the spark plugs, I use a 25:1 oil/fuel ratio.

But next couple things to check are mentioned above, will continue investigating and informing you guys, thanks again.

Edited by Rafinx
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OK well I took the boat out again yesterday and the whole time it did not want to get on the plane, which has led me to believe the carby main jet is blocked, allowing for slow idle speeds but no power when needed.

Edited by Rafinx
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