85 Mercury 150 hp. Won't accelerate

[Wizard Sleeve]

Hello ladies and gents. I am new to the forum. Figured since every time I do a Google search for boating related stuff it brings me here I might as well join.

Recently repowered my 20 ft thunderbird with a 1985 evinrude 150 hp 6 cyl outboard. Got it from a guy who bought and sold it but never had it on the water. He ran it for me on the muffs and it started fairly easy and idled strong. Compression test was good, new sparkplugs, impeller and cleaned carbs. When I got it on the water it started out running well but wouldn't accelerate past 15 mph or so. We found an issue with the throttle not being allowed to extend fully forward, corrected it and thought we were in good shape. Not so lucky.

Now the boat loses power when brought under a load. It seems to starve for something when pushed past 5 mph or so. A couple times early on it seemed to clear and jumped up to 15 or so, but then bogged down again. So we thought clogged carbs or something. Took apart/cleaned the carbs and they are immaculate. Changed the fuel line to rule that out.

I took it out after the carbs were cleaned it never got past 5 mph and often sputters and shuts down even at that slow speed. Starts back up and putters along.

Took it out again yesterday after the fuel line was changed and it is even worse. Won't get over 5 mph and regularly dies and needs to be restarted. I also noticed a (new I think) intermittent spitting/coughing
noise

Bad stator has been suggested by a couple colleagues.

Any help or advice would be greatly appreciated.
Thanks all!

 

[flyingscott]

When it's doing that pump the primer ball see if it accelerates if it does probably the fuel pump. Otherwise I would do a cyl drop test make sure they are all firing.

 

[mr 88]

Have you adjusted your low speed needles ? If you have them at spec then start with the top carb by opening the jet about a a 8th of a inch. Or imagine a clock face and move it ahead 2 hours. Then test and if the same move to the middle carb test and then the bottom. You then repeat until it accelerates correctly. These carbs have a poor transition circuit and by opening the jets you overcome that shortcoming...
Also,is it a evenrude or mercury in line 6 cylinder. Your heading says mercury and your post says evenrude, my suggestion is for a mercury tower.

 

[mr 88]

I meant to move the jets out,not ahead in the clock explanation.

 

[fhhuber]

Similar issues Johnson 150... turned out to be leaking fuel pump. It was pumping more air than fuel.

 

[Dukedog]

Also,is it a evenrude or mercury in line 6 cylinder. Your heading says mercury and your post says evenrude, my suggestion is for a mercury tower.

which one???

if '85 150 merc it will be V6

 

[Wizard Sleeve]

Whoops. My last motor was an evinrude. You are correct this is a merc 6 cyl tower. Thanks for all the responses. I will be working on it this week.

 

[jbcurt00]

FV: Please check your PrivateMessages. They can be accessed from the messages link to the left of your user name at the top right corner of any forum page. Thanks

 

[Wizard Sleeve]

FHHuber, when the fuel pump went bad in your outboard were there any visible signs of the issue. I took mine apart and everything looks clean, diaphragm is intact. Considering replacing it to be sure, but am having a hard time finding a new one.

It was suggested that I try cleaning the carbs again now that the fuel line was replaced. The old fuel line was badly corroded and gummy inside at the gas tank connection. Perhaps since I cleaned the carbs then ran it again thru the old line there might be more gunk in the jets. Gonna check that one off the list

 

[tommarvin]

Its spark or fuel, if you have spark, then you know its fuel.

 

[Faztbullet]

How about a pic as they didn't make a Inline 6 in 85????

 

[fhhuber]

FHHuber, when the fuel pump went bad in your outboard were there any visible signs of the issue. I took mine apart and everything looks clean, diaphragm is intact. Considering replacing it to be sure, but am having a hard time finding a new one.

It was suggested that I try cleaning the carbs again now that the fuel line was replaced. The old fuel line was badly corroded and gummy inside at the gas tank connection. Perhaps since I cleaned the carbs then ran it again thru the old line there might be more gunk in the jets. Gonna check that one off the list

There was some fuel always in under the carbs... I thought it was getting dumped when the engine was tilted ... No other visible symptom until I squeezed the primer bulb while looking at the pump... then I saw fuel coming out at the gaskets. Further inspection showed the pump casing was cracked.

You won't have the same pump... but squeezing the primer to apply pressure while looking at the pump won't hurt anything and if that makes fuel come out where it shouldn't, its potentially at least part of your issue.

Same symptoms... simple test that costs nothing.

 

[racerone]

The inline 6 was last listed in 1988 but not as a 150 hp model.---Need to post picture / serial # to see what you actually have !