need help! I've tried everything I can

[rxrgoose]

Hey guys
I've been reading through posts for a week trying to fix my problem and nothing seems to be working. When I start my boat runs beautiful. Get on the water and on the plane once. As soon as I Throttle Down I can't get above 1200 RPM without bogging down. It's a 1984 Evinrude 70 horsepower outboard. Revs fine in neutral with no load. I've replaced the power pack and rebuilt the fuel pump. Still have the exact same problem. Compression on all three cylinders is within 10% of 135 PSI. I have spark. Only thing I haven't done is rebuild the carbs because it's something I can't personally do. If it was a carb problem how would it run beautifully on plane the first time I give it throttle after starting it. Any help would be greatly appreciated. I've read similar post but people don't seem to update their post with information on whether what they tried worked or not.

 

[racerone]

Does spark jump a gap of 3/8" or more on all 3 , yes or no ?----In my opinion carburetors on those are easy to do !!

 

[rxrgoose]

I'm just confused with why it would run perfect for one pass if it was carbs

 

[interalian]

Try pumping the primer ball next time it won't go.

 

[BassinGas]

you can rebuild the carbs, it is easier than you think

 

[oldboat1]

Is it heating up after that first run? Top of the head shouldn't be too hot to touch.

 

[rxrgoose]

I will have to check if it gets hot. I'm taking it to have the carbs rebuilt on Thursday and that's the next time it will be on the water. I was hoping someone would say if it sounded like a fuel problem. I was also hoping someone could explain if it was fuel delivery why it would be fine for one round of open throttle then only run at 1200 rpm and under.

 

[racerone]

What if it does not run properly after getting carburetors " rebuilt "----Did you get a quote from the shop for that work ??

 

[oldboat1]

could be a linkage issue, maybe a problem with the remote throttle cable. Sounds like you are trying to talk yourself in or out of something. Carb rebuilding at a shop is expensive. We're not in the boat with you. If you have some doubts, why not do some more testing -- maybe consider rebuilding the carbs yourself, if it comes to that.

"Bogging down" can mean fuel or mechanical or electrical or a prop issue....lot's of things. You say you have spark, but you have to measure it as suggested above -- need a tester for that. Laying the plug on the block isn't enough:

 

[rxrgoose]

engine is new to me so I'd like to have the carbs done anyway and get them all tuned and synced up. I'm more interested in ideas as to why I get that good first run at wot before the problems start. wouldn't a linkage issue be an work or it doesn't sort of thing.

 

[oldboat1]

Well, cables can slip, particularly the old J+E type. And it could be heating up -- CD ignition parts can get wonky if old and overheating.

Anyway, post results.

 

[Dennischaves]

I did the carb rebuild on my 84 Evinrude 70hp
with help from this forum
It's very very easy there's nothing to adjust
The carb rebuild kit was $30 and a few hours of work
Take tour time 1 carb at a time take pics every step and don't mix up the carbs

 

[boobie]

Seeing you get that first good run, look more closely at the ignition system.

 

[rxrgoose]

Because it runs so beautifully on the first pass I feel like it's a heat triggered problem. What components in the ignition system are prone to failure when hot?

 

[racerone]

Here is a simple / no money spent / do it yourself test.------Remove cover in front of carburetors.-----Have an assistant drive the boat.----Now look into each carburetor bore when motor acts up.----Strong flashlight must be used for proper results on this test.----Compare amount of fuel coming up the main nozzles.

 

[rxrgoose]

carb rebuild is done and link and sync. same issue. am I better to just move on from this motor?

 

[racerone]

Did you look at the reed valves when carburetors were off, yes or no ?-----Have not seen an answer on spark intensity.----Does spark jump a gap of 7/16", yes or no ?-----These are an excellent / simple motor to maintain and fix !!!

 

[rxrgoose]

haven't done spark test yet. waiting on delivery of the tester. how do I test spark when it happens on the water? the tester I'm getting is an inline tester with adjustable gap.

 

[rxrgoose]

I didn't do the rebuild of the carbs I'd have to ask if they looked at the reeds

 

[rxrgoose]

just got the boat back. they can not tell me why but there is a fuel issue. they checked compression and spark at point of failure and everything checked out. they are baffled. they can guarentee it's not the carbs fuel pump or fuel tank and lines. they also said it is for sure heat triggered.