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Author Topic:   troubleshooting 70 hp Evinrude

HookedOnHer posted 12-03-2002 10:58 PM ET (US)
I have a 70 hp Evinrude that runs great!!Wot is @ 5200 rps. The age of motor is a 1980 model. When cold,..choke it and it starts right up. My problem is after it has been running and I stop to fish for hour or more I have to choke it agian, just like it has not been started at all. I have to also use the idle trottle when starting. I have changed tanks,fuel lines and added in-line fuel filter. Other then looking new this has not had any effect on this. Big I know you will say carbs need cleaning but I have no loss of power after start, no missing or low spots in throutle. At idle it doesn't miss or loose power when cold starting only after motor is warm. I have just moved and don't know of a good shop so I want to have an idea what is wrong when I take it in. It seems like ther is a seal inside that is letting it loose its vacum? Like a bad fuel ball would act but inside motor??
whalerron posted 12-04-2002 12:01 AM ET (US)
How is the compression on that motor?
Matthew posted 12-04-2002 12:03 AM ET (US)
I had similar experiences with my '81 70 omc.
I did not have to choke it after an hour but had to lift the fast idle lever slightly. Never thought to look for something wrong just thought that was the nature of the beast.
Matt
Steve Leone posted 12-04-2002 12:50 AM ET (US)
How cold is it when this happens? If it is cold this would be normal. If it does not run rough at idle and performs properly at mid and full range then it is unlikely a crank seal. I would definitely, primarily, allways without a question do a leak down compression test first and foremost. It might save you a whole lot of guesswork. Generally if you have a crank seal leak the culprit is the lower one. A good indicator that the lower seal is weak or gone is to look at the water pick-up or exhaust outlet at the prop hub. If there is alot of snot (oil mixed with water and exhaust) running out at these points then you more than likely have a seal problem. If the top seal is poor then you will get an oily residue all over the top of the powerhead. Sort of a fuel-mix volcano if you will. This can really gum up the electronics also. If the compression pans out try this. If your outboard carbs are equiped with adjustable needle and not fixed jet then follow these steps. 1) Gently turn the scews in one at a time counting 1/2 turn at a time untill lightly seated. Write down each total for each carb(example "top carb 1 1/4 turns"in etc.) 2) Now remove all of the needles. 3)Grab a can of Power Tune. Mercury puts it out. It comes with a long pice of plastic straw. Fit the straw into the nozzle of the power tune can. Insert the straw into the idle mixture hole and press. Count to 5 and stop. Do this with all 3 carbs. 4) Replace all of the needles and lightly seat them. Turn them out as many turns as you turned them in when you started. Run the engine for at least minutes at a high idle. Go try it and see if it remedies the problem. Sorry for the book, Steve
Clark Roberts posted 12-04-2002 07:54 AM ET (US)
Steve, very good advice and clear description! Hooked, try a basic tune up(new plugs properly gapped) and "link and sync" (all throttle and timing adjustments) ... Happy Whalin'.../ Clark.. Spruce Creek Navy
Bigshot posted 12-04-2002 11:48 AM ET (US)
If it aint compression, gotta be carbs or something fuel related. I would not say a rebuild but a link & Synch is probably in order, could be a cracked reed valve, etc.
Seabrook posted 12-04-2002 12:24 PM ET (US)
HookedOnHer, while it is hard to top the expert advice you have already received on the topic, I will provide my humble opinion anyway. Through the years I have owned two 3 cyl OMC motors of similar similar year models to yours. Both ran great at idle, mid range and WOT. However, both required to use the fast idle and a little choke to start quickly after sitting for an hour or more. I will tell you what the mechanics told me then "Don't try to fix it because it aint broken". That is very typical for that motor in that age class. Go back a few more years and you often had the opposite problem. If you were not very careful, you would flood them. For me, it was never a problem. Just bump up the idle and choke her for a second.
HookedOnHer posted 12-04-2002 02:09 PM ET (US)
Seabrook I have to agree with you on the advice that I am getting from the form. I also am thinking your advice over hard. I had a tune-up when I bought the rig, and same time had comp test ran with in range. I have been living with this for a year now. I was concerned about getting stranded because it is very easy to flood the motor when you need a fast start. I will look over all the advice and start weeding out the none problems. Any other ideas from the form are welcome.
Seabrook posted 12-04-2002 04:31 PM ET (US)
HookedOnHer, don't worry about flooding the older pre-mix motors and getting stranded. There is a real easy fix for that. If you ever get the motor flooded, disconnect the gas line at the motor,push the fast idle all the way up and turn the motor over several times(allowing the starter motor to cool between each time). This will push all the gas through your motor. It will usually either crank up, or try to crank once you get enough of the gas through. Then connect your gas line back and you are good to go. I love the older pre-mix motors. If you maintain them properly, I have more faith in older ones getting me home than the newer injected motors.
NedsPoint posted 12-05-2002 11:41 AM ET (US)
Hooked/et al;
I have a 1986 Johnson 70 hp. I suppose it acts similiar, but whats the big deal? The engine still warms up and runs great. Sometimes it loads up with oil after trolling, etc, and I have to throttle it out of it. I never considered the symptons you mentioned a problem. As a matter of fact (knock on wood) I think the engine is one of the better running ones I've owned in 30+ years of boat ownership.
HookedOnHer posted 12-05-2002 03:47 PM ET (US)
Nedspoint, I know I have a great motor at 23 years old. The comp and preformance like I said before is great. I to have had my share of motors good and bad. I got the info I was hoping for from the forum. Now this winter I can use my time more wisley. Thanks agian to all who shared their opinions.

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Author	Topic: troubleshooting 70 hp Evinrude
HookedOnHer	posted 12-03-2002 10:58 PM ET (US) I have a 70 hp Evinrude that runs great!!Wot is @ 5200 rps. The age of motor is a 1980 model. When cold,..choke it and it starts right up. My problem is after it has been running and I stop to fish for hour or more I have to choke it agian, just like it has not been started at all. I have to also use the idle trottle when starting. I have changed tanks,fuel lines and added in-line fuel filter. Other then looking new this has not had any effect on this. Big I know you will say carbs need cleaning but I have no loss of power after start, no missing or low spots in throutle. At idle it doesn't miss or loose power when cold starting only after motor is warm. I have just moved and don't know of a good shop so I want to have an idea what is wrong when I take it in. It seems like ther is a seal inside that is letting it loose its vacum? Like a bad fuel ball would act but inside motor??
whalerron	posted 12-04-2002 12:01 AM ET (US) How is the compression on that motor?
Matthew	posted 12-04-2002 12:03 AM ET (US) I had similar experiences with my '81 70 omc. I did not have to choke it after an hour but had to lift the fast idle lever slightly. Never thought to look for something wrong just thought that was the nature of the beast. Matt
Steve Leone	posted 12-04-2002 12:50 AM ET (US) How cold is it when this happens? If it is cold this would be normal. If it does not run rough at idle and performs properly at mid and full range then it is unlikely a crank seal. I would definitely, primarily, allways without a question do a leak down compression test first and foremost. It might save you a whole lot of guesswork. Generally if you have a crank seal leak the culprit is the lower one. A good indicator that the lower seal is weak or gone is to look at the water pick-up or exhaust outlet at the prop hub. If there is alot of snot (oil mixed with water and exhaust) running out at these points then you more than likely have a seal problem. If the top seal is poor then you will get an oily residue all over the top of the powerhead. Sort of a fuel-mix volcano if you will. This can really gum up the electronics also. If the compression pans out try this. If your outboard carbs are equiped with adjustable needle and not fixed jet then follow these steps. 1) Gently turn the scews in one at a time counting 1/2 turn at a time untill lightly seated. Write down each total for each carb(example "top carb 1 1/4 turns"in etc.) 2) Now remove all of the needles. 3)Grab a can of Power Tune. Mercury puts it out. It comes with a long pice of plastic straw. Fit the straw into the nozzle of the power tune can. Insert the straw into the idle mixture hole and press. Count to 5 and stop. Do this with all 3 carbs. 4) Replace all of the needles and lightly seat them. Turn them out as many turns as you turned them in when you started. Run the engine for at least minutes at a high idle. Go try it and see if it remedies the problem. Sorry for the book, Steve
Clark Roberts	posted 12-04-2002 07:54 AM ET (US) Steve, very good advice and clear description! Hooked, try a basic tune up(new plugs properly gapped) and "link and sync" (all throttle and timing adjustments) ... Happy Whalin'.../ Clark.. Spruce Creek Navy
Bigshot	posted 12-04-2002 11:48 AM ET (US) If it aint compression, gotta be carbs or something fuel related. I would not say a rebuild but a link & Synch is probably in order, could be a cracked reed valve, etc.
Seabrook	posted 12-04-2002 12:24 PM ET (US) HookedOnHer, while it is hard to top the expert advice you have already received on the topic, I will provide my humble opinion anyway. Through the years I have owned two 3 cyl OMC motors of similar similar year models to yours. Both ran great at idle, mid range and WOT. However, both required to use the fast idle and a little choke to start quickly after sitting for an hour or more. I will tell you what the mechanics told me then "Don't try to fix it because it aint broken". That is very typical for that motor in that age class. Go back a few more years and you often had the opposite problem. If you were not very careful, you would flood them. For me, it was never a problem. Just bump up the idle and choke her for a second.
HookedOnHer	posted 12-04-2002 02:09 PM ET (US) Seabrook I have to agree with you on the advice that I am getting from the form. I also am thinking your advice over hard. I had a tune-up when I bought the rig, and same time had comp test ran with in range. I have been living with this for a year now. I was concerned about getting stranded because it is very easy to flood the motor when you need a fast start. I will look over all the advice and start weeding out the none problems. Any other ideas from the form are welcome.
Seabrook	posted 12-04-2002 04:31 PM ET (US) HookedOnHer, don't worry about flooding the older pre-mix motors and getting stranded. There is a real easy fix for that. If you ever get the motor flooded, disconnect the gas line at the motor,push the fast idle all the way up and turn the motor over several times(allowing the starter motor to cool between each time). This will push all the gas through your motor. It will usually either crank up, or try to crank once you get enough of the gas through. Then connect your gas line back and you are good to go. I love the older pre-mix motors. If you maintain them properly, I have more faith in older ones getting me home than the newer injected motors.
NedsPoint	posted 12-05-2002 11:41 AM ET (US) Hooked/et al; I have a 1986 Johnson 70 hp. I suppose it acts similiar, but whats the big deal? The engine still warms up and runs great. Sometimes it loads up with oil after trolling, etc, and I have to throttle it out of it. I never considered the symptons you mentioned a problem. As a matter of fact (knock on wood) I think the engine is one of the better running ones I've owned in 30+ years of boat ownership.
HookedOnHer	posted 12-05-2002 03:47 PM ET (US) Nedspoint, I know I have a great motor at 23 years old. The comp and preformance like I said before is great. I to have had my share of motors good and bad. I got the info I was hoping for from the forum. Now this winter I can use my time more wisley. Thanks agian to all who shared their opinions.