surging issue

[bob johnson]

I have a 1996 johnson 70 hp. It started surging about 4 trips ago and it seems to have gotten worse. I have a new moeler 12 gallon tank(actually used last season too) its direct plumbed to the motor cover where there is a j-e connecter. It has 3 year old fuel line from Shields A1 premium fuel hose. I took the boat out today left the ramp and ran up to 4500 rpms and it was humming, then after about 45 seconds it started surging and choked me down to about 3000 rpm ... later it dropped to the mid 2000's. temps ate the top of the head were 145 when it started , I have found I think the lower part of the head is hotter. any chance this issue is electrical in nature...or a fuel-air leak issue?

 

[bob johnson]

and the oil line is plugged off....so i know the NO OIL light is on...always is

 

[Crosbyman]

best to clear the "hotter" issue asap. impeller ???
tank venting ok ??? open the fuel cap
carb (s) clean ??

running pre-mix ?? why not fix the oiler issue ??

 

[bob johnson]

best to clear the "hotter" issue asap. impeller ???
tank venting ok ??? open the fuel cap
carb (s) clean ??

running pre-mix ?? why not fix the oiler issue ??

brand new impeller, the kits are superceeded and cover a lot of modles. Paperwork says you dont need some of the parts(o-rings) even though the original factory manual says use them.... the tell tale is shooting 8 feet in a straight line!.... Im wondering if I have blockage in the head itself. im running premix.... I have even removed the fuel tank cap... carbs cleaned 3 years ago... does a dirty carb cause SURGING???... insufficent fuel supply might or an air leak, but I dont know if a bad electrical compnent can cause this issue!

 

[bob johnson]

this was today before I went to the lake! you just can get a better stream from the tell tale.....

 

[dingbat]

Surging isn’t electronic.
Anytime a motor is surging you have to be looking for air or vacuum leaks.

Still running OE fuel pump?

Run a fuel line off fuel pump intake. Drop other end in a can of fuel to see if it stops.

 

[saltchuckmatt]

Did you try pumping the primer ball when it was surging?

 

[tphoyt]

How old is the fuel?
Just for kicks pull your fuel line and pump some into a glass jar to check for water.

 

[racerone]

Post the compression numbers.----Test for strong spark.

 

[bob johnson]

Did you try pumping the primer ball when it was surging?

I did, no change

 

[bob johnson]

Post the compression numbers.----Test for strong spark.

130, 130, 127..... didnt check spark.....

 

[bob johnson]

How old is the fuel?
Just for kicks pull your fuel line and pump some into a glass jar to check for water.

the fuel is a day old..... well have the tank, the other half was from 4 days ago...

 

[bob johnson]

Surging isn’t electronic.
Anytime a motor is surging you have to be looking for air or vacuum leaks.

Still running OE fuel pump?

Run a fuel line off fuel pump intake. Drop other end in a can of fuel to see if it stops.

ill try that

Surging isn’t electronic.
Anytime a motor is surging you have to be looking for air or vacuum leaks.

Still running OE fuel pump?

Run a fuel line off fuel pump intake. Drop other end in a can of fuel to see if it stops.

That's a good idea but logistically it's difficult,because my issue arises when trying to go over 3000 rpm AFTER about 45 seconds. It doesn't surge at idle or below 2000 rpm. So to rig a tank and hose and a temp line, then take the boat out on the water...doable but not easy alone. So that's a test to see if all the connections and fuel lines inside the motor cover are bad!!! Right

 

[racerone]

Run with a timing light.-----One cylinder at a time.----See if you have steady spark as you speed up.

 

[bob johnson]

I have a 1996 johnson 70 hp. It started surging about 4 trips ago and it seems to have gotten worse. I have a new moeler 12 gallon tank(actually used last season too) its direct plumbed to the motor cover where there is a j-e connecter. It has 3 year old fuel line from Shields A1 premium fuel hose. I took the boat out today left the ramp and ran up to 4500 rpms and it was humming, then after about 45 seconds it started surging and choked me down to about 3000 rpm ... later it dropped to the mid 2000's. temps ate the top of the head were 145 when it started , I have found I think the lower part of the head is hotter. any chance this issue is electrical in nature...or a fuel-air leak issue?

So no one is mentioning the fuel pump itself. Is that likely to mean surging isn't caused by a bad fuel pump....or surging isn't a symptom of a failing fuel pump

 

[racerone]

If you pump the bulb and there is no change , then the pump on the motor is working properly !!

 

[saltchuckmatt]

Surging could be electronic....if your dropping a cylinder it will surge.

Have you examined the spark plugs? The can tell a story.

 

[bob johnson]

Surging could be electronic....if your dropping a cylinder it will surge.

Have you examined the spark plugs? The can tell a story.

they did not look bad.... not fouled...a little dark, but not sooty.... they were dry!

 

[tphoyt]

Have you checked for water in your fuel?
Don’t mean to beat you up but I see it all the time and people don’t believe it could be the problem.

 

[bob johnson]

Have you checked for water in your fuel?
Don’t mean to beat you up but I see it all the time and people don’t believe it could be the problem.

not specifically because the 12 gallon tank is full right now...BUT the motor starts and idles perfect... and when I take off initially with the boat and can get up to 30 mph and run about 4500 or more rpms for almost 1 minute...THEN the surging starts.... would the water in the tank PREVENT that?