Rafinx Posted June 14, 2011 Share Posted June 14, 2011 (edited) 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 June 14, 2011 by Rafinx Link to comment Share on other sites More sharing options...
a boat Posted June 14, 2011 Share Posted June 14, 2011 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. Link to comment Share on other sites More sharing options...
Marlin01 Posted June 14, 2011 Share Posted June 14, 2011 Rafinx, Possibly power packs have failed due to higher loads Check colour and intensity of spark. Other than that as Huey said work your way through the possibilities. And good luck Marlin01 Link to comment Share on other sites More sharing options...
cheap charlie Posted June 14, 2011 Share Posted June 14, 2011 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? Link to comment Share on other sites More sharing options...
cheap charlie Posted June 14, 2011 Share Posted June 14, 2011 You say the issue develops once warm? Is the choke on to such time or purely.just used to.fire the engine ? Did you use hotter or cooler plugs then standard? Link to comment Share on other sites More sharing options...
The Incredible Hull Posted June 14, 2011 Share Posted June 14, 2011 (edited) check your reed values, they might be dirty, and perhaps not closing, causing it to run rich and have crappy compression (I think its behind the carb) Edited June 14, 2011 by dpham Link to comment Share on other sites More sharing options...
Rafinx Posted June 14, 2011 Author Share Posted June 14, 2011 (edited) 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 June 14, 2011 by Rafinx Link to comment Share on other sites More sharing options...
greg123 Posted June 14, 2011 Share Posted June 14, 2011 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 Link to comment Share on other sites More sharing options...
Rafinx Posted June 14, 2011 Author Share Posted June 14, 2011 Well at the moment I think it needs a new fuel tank, so may aswell get it, and get some new fuel with it. Ill have to see. Thanks guys for giving me stuff to go on. Link to comment Share on other sites More sharing options...
Geoff Posted June 14, 2011 Share Posted June 14, 2011 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 Link to comment Share on other sites More sharing options...
Rafinx Posted June 14, 2011 Author Share Posted June 14, 2011 that sounds just about right Its ok for the inital start off, but when for example I move spots it starts to do it. Very strange never seen it in cars. Link to comment Share on other sites More sharing options...
Geoff Posted June 15, 2011 Share Posted June 15, 2011 (edited) 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 June 15, 2011 by Geoff Link to comment Share on other sites More sharing options...
The Incredible Hull Posted June 15, 2011 Share Posted June 15, 2011 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. Link to comment Share on other sites More sharing options...
Geoff Posted June 15, 2011 Share Posted June 15, 2011 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. Link to comment Share on other sites More sharing options...
cheap charlie Posted June 15, 2011 Share Posted June 15, 2011 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 Link to comment Share on other sites More sharing options...
Rafinx Posted June 17, 2011 Author Share Posted June 17, 2011 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. Link to comment Share on other sites More sharing options...
Rafinx Posted July 17, 2011 Author Share Posted July 17, 2011 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? Link to comment Share on other sites More sharing options...
Brooker435 Posted July 18, 2011 Share Posted July 18, 2011 This is Interesting as when I had cooling problems with my 1975 Evinrude 50 the buzzer would go off once it was too hot but you still had power allthough I cut the power off as soon as I heard the buzzer, perhaps your buzzer is not working or does not exist. I would go through the basics first as many people have suggested, once you have exhausted all avenues check the cooling system and see how you go. when the motor starts cutting out perhaps you should feel it see how hot it is carefully as maybe if there is a cooling issue the water might not be getting to the right places. I will be interested to know how you go with this, Good Luck, Regards, Nathan Link to comment Share on other sites More sharing options...
helliconia Posted July 18, 2011 Share Posted July 18, 2011 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. Link to comment Share on other sites More sharing options...
Brooker435 Posted July 18, 2011 Share Posted July 18, 2011 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. Yes they do have thermostats well my 50 HP does, the thermostat is not the only possiblilty to this problem but plays a vital role in the cooling system definately worth checking out if this is a cooling issue, Regards, Nathan Link to comment Share on other sites More sharing options...
Rafinx Posted July 18, 2011 Author Share Posted July 18, 2011 funny u should say that, the guy i bought it off removed the thermostat completely lol. Link to comment Share on other sites More sharing options...
Red Posted July 19, 2011 Share Posted July 19, 2011 Have you checked the fuel pump diaphram? Cheers Red Link to comment Share on other sites More sharing options...
hookmeup Posted July 19, 2011 Share Posted July 19, 2011 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 $$$$$$$ on research & development wouldn't put it in there if it didn't need it for the benefit of the motor in the long run. just my midday rant !! Link to comment Share on other sites More sharing options...
Alastair Posted July 21, 2011 Share Posted July 21, 2011 Straying off the topic I know but, me & my mate have had this argument before, his thermostat was RS & new one was incredibly pricey(compared to automotive) , about $50, so he thought I'll just chop the middle out & run without, engine runs fine but they are designed to get the motor up to the ideal running temperature quicker & me thinks these big companies who spend serious $$$$$$$ 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? Link to comment Share on other sites More sharing options...
Zdenk01 Posted July 21, 2011 Share Posted July 21, 2011 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. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now