do i have one problem or two?

[tbharris]

I have a 1976 Evinrude 70hp model 70673D. It idles perfect, but does not have enough power to plane - seems to bog down. The time it was run just prior to this, it ran perfectly. Here is the wierd part..... I took it out of the water (right when this happened) to change the lower unit oil - it was PRESSURIZED, black, and smelled burned. I mean really pressurized - blew all over me and the back of the boat. There were a few pieces of metal in the oil - bigger than flakes, but not huge chunks.

I changed, and rechanged the lower unit oil 3-4 times, and ran it gently on the muffs. Semmed ok. I water tested - same syptoms without the oil pressure problem.

Is this a lower unit issue, or engine or both? Where to start diagnosing?

Thank you!!!

 

[Chinewalker]

Re: do i have one problem or two?

Some fine metal shavings - visible to the eye but not really able to be felt on your fingertips - is normal. If you're getting anything more than that you've got an issue inside the unit. I don't think it is related to your running issue, though...

That sounds more like you're running on less than three cylinders. Could be an ignition issue, could be a fuel issue (each carb feeds one cylinder). Do not run it any more until you determine what's going on as a fouled carb could lead to a blown motor...

 

[ezeke]

Re: do i have one problem or two?

Be careful when refilling the gearcase that you don't overfill; stop when the oil flows out of the vent hole.

Black oil is worn out. Are you using high viscosity oil?

The engines can sound fine running on two cylinders with no load; do a compression test and a spark test, then run with an inductive timing light so that you can "read" the spark across the range of RPM.

 

[tbharris]

Re: do i have one problem or two?

Thanks - i'll start with the compression test, spark and timing light as suggested.