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I have a 1978 or 79 Evinrude 70hp outboard, on the last trip to the lake it wasn't wanting to stay running unless I held the choke in. Once I let the choke go it was almost as if it was burning all the gas it had in the carb. then would die, After about a 1 1\2 hour it finally stayed running. I've never experienced this out this boat.
I would say you either have some trash in the carbs or the fuel pump needs to be rebuilt. Start with the fuel pump as it is a cheap and easy job.
Check simple things first. Make sure the vent is venting. Check bulb and fuel line for cracks or bad check valve in bulb. Check VERY closely! Does it pump up firm before you start it? There is an inline filter on those engines...if you have never changed it...change it. Also check fuel pump...its has a small screen in it also. As Bill stated...they are very easy to change out...and cheap.
Normally on engines that you have to push the choke in to run you have an air leak somewhere...carb to intake gasket etc...the air seeping in will lean it out...hence running with choke in which gets the air/fuel ratio to a point it will burn.....or and more times than not....a clogged jet in one or more carbs. Does it do it at idle only...all the time...or could you run it down the lake but not idle?? Does the same as an air leak...but the other direction...its getting too much air because the jets are not allowing the fuel to come through...so again...it leans out and you push choke in which gets the air/fuel ratio back to where it will burn.
How old is the gas?? Have you ran any seafoam through it? Could of gotten some trash in a carb then it passed it...why it started running right later on in the day.
If fuel lines, bulb, vent, filter, etc check out then I'm leaning to time to rebuild carbs.
Have to choke it almost assures that its a fuel problem.
When I was on the lake it wouldn't get out of idle till after I played with it for a while idling half way down the lake then it just took off. The bulb never loss its prime, I got gas earlier that day, haven't tried seafoam yet. If the cost of fuel pump is cheap enough ill go ahead and change it and the filter just for safe measures. Thanks for the feedback, ill let y'all know how it goes.
Really sounds like it passed some trash. Do you have a filter/water separator on it? Would be a good investment if not.
No sir, but I was just reading the seafoam thread and was looking at the filter/water separator someone posted and thought about buying one in the next few weeks when my budget allows, seemed like a good preventative action to take.
I think I would rebuild the carbs also. Its not a hard process. Its time consuming...but not hard. That way you know everything is clean and ready to go. You will most likely not have any trouble again after that. check the screen in the fuel pump and the little inline filter also.
How long did you run it after it started running right?? Did it do it anymore?
I ran it about 15 min. Then I cut it off, started and ran fine the rest the day till we went to put it on the trailer. I'm ordering a rebuild kit for fuel pump this week. I might just remove the carb. and soak it for a few days then clean it up.
If you can, pull the bowl off the carb and check for trash in the bottom of it.
+1 on what cray said. Simply soaking it without taking it apart will not get the trash out of it. You need to take it apart...soak it...then blow through all the orifices with air until clean. Then I would go ahead and put new jets (rebuild kit) on it.
I would suggest berryman carb cleaner in the gallon. That is some great stuff...pricey but great.
Another thing...if I remember right you have three carbs...if one is causing the problem. Lets say one is lean compared to the rest. That ALSO means that one is lean on oil. So that cylinder is not being lubricated as well as the other two. Running a multiple carb engine with one running lean is bad. And will eventually take that cylinder down. If it were me I would tear them all down, soak them overnight in berryman, blow them out and rebuild them.
Just my two cents.
Yeah I'm going to take carbs off tom. And rebuild them. Is rebuilding the carbs the same as rebuilding a four wheeler or dirt bike, I've never really messed with boat motors. Thanks Cray and Scrapper.
Yes, they are very similar. Not hard. Just three of them instead of one. I do recommend getting a (oem) manual so you can link and synchronize the carbs correctly. You can get them online. Or just google it. You can find the process all over. But I do recommend the manual. What synchronizing will do is put all three carbs opening at the same time, and having the idle air right on all three. You will also set the timing when you do this. Its not hard. Just takes a little time.
Take your time, be very particular with your cleaning. Then make sure you put the water/fuel sep on it before firing it back up.
Let us know if you need anything.
There will be a procedure in your manual called Link & Sync. This sets all your linkage and timing so they work properly. It is very important that it is done in the order given in the manual.