1978 150 hp evinrude problems

[charlie1975]

hey guys,so ok i took out my boat yeterday and everything started good,ran great,im hauling *** down the ohio river about 45 mph.stopped and fished for a while.go to leave and now motor is acting all crazy.first off it will start right up,but when i go the put in forward it wants to like sputter alittle and then die.go thru this routine many many times until it finally takes off.So im back on the river now with the throttle wide open and it wont go any faster now than about 20 mph..not sure what could of happened....any ideas

 

[boobie]

Re: 1978 150 hp evinrude problems

First, check your compression and then your spark. Spark should jump a 7/16 " open air gap.

 

[emdsapmgr]

Re: 1978 150 hp evinrude problems

Follow boobie's recommendations. Likely you are not getting spark to all 6 cyls. That engine will seem to run fine on 4 or 5 cyls, but needs all 6 firing when in gear in the water. Keep in mind that weak ignition componets tend to fail once the engine heats up to normal operating temps. May run fine when cold.... That engine has twin power packs on it. They can be swapped for testing purposes.

 

[charlie1975]

Re: 1978 150 hp evinrude problems

ok great advice guys..thanks...couple questions ..this is only 3rd run since last replacing plugs,could they foul out that quickly,and when doing compression check what should the compression be...thanks again

 

[emdsapmgr]

Re: 1978 150 hp evinrude problems

When new, that engine probably had compression in the 110 lbs range- on all 6 cyls.

 

[charlie1975]

Re: 1978 150 hp evinrude problems

ok guys just done compression test and these are the results #1- 85 #3 -75 #5 -100 #2 -90 #4-90 #6-90 what do u think

 

[emdsapmgr]

Re: 1978 150 hp evinrude problems

Compression below the 110 lbs is not necessarily a condemning factor in itself. Another guideline is that the compression on all cylinders should be within 10% of each other. In your engine you have a couple of cylinders on the starboard head which are outside that tolerance guideline. I'd probably pull that head off and see if the seal rings on the head gasket are leaking on #1 and #3 cyls. That will also give you the opportunity to visually inspect the piston and head faces and check the top rings.

 

[charlie1975]

Re: 1978 150 hp evinrude problems

any kinda manuals available on here to guide me thru this...will be my first head job....that doesnt sound very good...lol thanks

 

[charlie1975]

Re: 1978 150 hp evinrude problems

and how will i know if the rings are leaking

 

[charlie1975]

Re: 1978 150 hp evinrude problems

if im gonna open this thing up im feeling that i should go ahead and change all the rings...would u recommend that or not

 

[ondarvr]

Re: 1978 150 hp evinrude problems

You can't change the rings doing this, it's far more complicated. The head gasket is about $25.00, you will need two of them if your remove both heads.

Do the plugs all look the same, or are some a little different. Dark and wet may mean they aren't firing correctly, or at all, white means it may be running lean.

You may need to put it back in the water and see if you can detect which cylinders aren't firing when it's warm (if this is the issue).

 

[charlie1975]

Re: 1978 150 hp evinrude problems

there were a couple of plugs that were pretty dark,completely covered on the ends ..and a couple not as dark..i believe there were two that looked as clean now as the day i put
them in

 

[emdsapmgr]

Re: 1978 150 hp evinrude problems

If you are going to do your own maintenance, then get an original 1978 factory service manual. All other manuals are not worth your expenditure. go to this website: outboardbooks.com

 

[charlie1975]

Re: 1978 150 hp evinrude problems

a few yrs ago i had another boat with a 85 hp merc motor i bought a service manual from a local marina, the gentlemen told me it was the same type they use at the marina to service their boats and suppose to tell everything.im asking this because i paid $90 for it and the site you mentioned its only $50.cheaper is great but just wanting to make sure .......thanks

 

[emdsapmgr]

Re: 1978 150 hp evinrude problems

Most Merc manuals are around $75 from the factory. If you paid for freight and tax, that might be about right. You'll get the correct Evinrude factory service manual from that website. If you feel unsure of ordering on the web, call Ken Cook, Inc. direct. They are in Milwaukee. 414-466-6060.

 

[charlie1975]

Re: 1978 150 hp evinrude problems

u guys are awesome..thanks for all the help