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73b 65HP Lower unit What to replace

J

jim18611865

Regular Contributor
"We managed to get it started

"We managed to get it started after 17 years sitting. Now lower unit is off and I am taking pictures. I will replace intake screen(broken) and water pump kit and lower unit oil. What other "no brainer" parts should I replace while I have it off. An o-ring(also broken) fell out of the housing while wheeling the upper back into the garage. I think this goes on the upper end of driveshaft?
It shifted in and out of reverse and forward while running, with no indication of problems.
Eventual plan is to boat test, and see how bad the low compressing cylinder (100/100/80) is and likely get the upper rebuilt after I know I will make the boat go."
 
"Grease the top splines and in

"Grease the top splines and install a O Ring in the groove just under those splines. Eliminating this step will result in having the driveshaft and crankshaft splines eventually rust together.

Use only "Premium Blend", also known as "Type C" gearlube in that unit, available only at your local Evinrude or Johnson dealership.

Low compression is usually caused by having a carburetor somewhat clogged OR weak erratic ignition. Hopefully you've cleaned and rebuilt all of the carburetors. If not, I suggest you do so."
 
Mine is not an electric shift.

Mine is not an electric shift. Should I still use the Type "c" fluid? Model 65373R
I redid all the carbs. No way this ever would have run. Black tar like substance in them.
Also reading the specs in the OMC manual I noticed a possible problem. I did not take care to keep in original place the low speed orifice and the idle restriction plug. They are apparently not exact? Will this be any trouble? (pg. 2-2)
This was not my boat so I really do not know what caused the low compression. Maybe if I am lucky a head gasket will be the problem.
 
"Although your engine is not a

"Although your engine is not an electric shift model, it does incorporate an oil pump which is used with what is called a Shift Assist set of solenoid like plungers. The OMC manual should depict a graphic of the vertical plunger assembly and the oil pump.

Due to this design (oil pump), the Preminum Blend (Type C) gearlube is required.

The idle orifice is the brass fixed high speed jet that goes in the front top portion of the upper carburetor body. All three (3) orifices are the same size so it doesn't matter which carburetor they are installed into.

The idle restriction plug is simply the long screw plug with the red sealing washer. All of these are identical also."
 
"Good thing you said something

"Good thing you said something. Oil is on the list now.
I worked on the carbs one at a time.
So each one could have the two orifices swapped, or not? Low speed (318823)hole size is .031" and the idle(318832) one is .035"
I don't think we are talking about the same thing."
 
"The larger jet in physical si

"The larger jet in physical size as well as the inside diameter size which is located in the bottom center of the float chamber is a "High Speed" jet.

The smaller fixed brass idle jet is located within the threaded hole at the top forward portion of the upper carburetor body.

There are only two (2) jets each in those carburetors. The top (idle) jet is part number 318823, is marked 31 and the ID size is .031. The high speed jet is part number 317330, is marked 59C and the ID size is .059 .

I'm at a complete loss to understand what you are explaining to me. Have you installed later model carburetors or higher horsepower carburetors on that engine that has a idle speed jet, an intermediate speed jet, and a high speed jet?"
 
"As far as I know the carbs ar

"As far as I know the carbs are original. Part #'s were correct. I found a second orifice "identical" or so I thought to the low speed orifice in the upper housing where the housing meets the bowl, in the high speed path.
My original OMC manual mentions the orifices in the specs page, but does not show the 2nd orifice on the exploded diagram.
Engine did start easily after rebuild, even with the low compression cylinder.
I asked about the part in an earlier post, but was told that is the way they were made, but no one indicated the two were different.
.004 I would think would be difficult for the engine to notice, but I could be wrong.

http://www.marineengine.com/discus/messages/12478/114938.shtml"
 
"Jim.... Okay, I understand wh

"Jim.... Okay, I understand what you speak of now. That jet that screws upwards into the upper body is part number 318832 and is marked (or should be marked) 35. The inside diameter is .035.

My apologies for the oversight of that secondary idle jet. It's been so long since I worked on that model carburetor that it had slipped my mind. Your mention of its location brought it back into view."
 
"So do I have anything to worr

"So do I have anything to worry about?
50/50 shot each one was swapped.
Should I tear them apart and check orifices?
I saw no markings.
No need for apologies, since I should have read more before tearing apart!
Worst case I could buy 6 new pieces and replace all."
 
"Would the low speed be marked

"Would the low speed be marked "31"?
If so I will pull those since I don't need to take carb apart to do it, and I will see how many I messed up."
 
"Jim, the " low compressio

"Jim, the " low compression " on one cylinder should be a MAJOR concern.There is not much point in spending money and time on carburetors / lower unit etc if the motor turns out to be in poor health internally ( scored cylinder or bad and damaged bearings) and it could be scrap."
 
"I have already checked and fo

"I have already checked and found a place to rebuild the powerhead for $1300. New engine is $8-10K. Before I spent the $1300 I wanted to see if all else is OK including lower unit.
I may end up spending $3-4K total on this engine, but the education is priceless, and parts seems to be available."
 
"The top slow speed jet would

"The top slow speed jet would be marked 31. Removing them would tell the tale, and yes, they must be in their proper locations.

I had assumed that you had an overhaul scheduled at some time in the future with that 20 psi diffrence."
 
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