'84 115hp T-o-P rebuild

[Venomous Duck]

I have an '84 115hp Tower of Power that i am pretty sure has a bad head gasket. Pressure test shows psi borderline spec when cold but way low on one cylinder (6 if I recall) when warm. I ordered a service manual off of Ebay and have done far too many auto rebuilds, so i decided to tackle this myself. What would you guys recommend as a "must do" while I have it apart? Should I do rings and need to hone for crosshatch or is that not needed for a 2 stroke? Should I buy a full gasket set (still trying to figure out the part number for the set) or just what i need to accomplish the head? Are there any specialty tools that are a must have an typical automotive garage wouldnt have? Most important if I wait until the season is over to do it, will I do any long term damage if I run it as is a few more times this summer? Any advice would be appreciated.

Thanks

 

[roscoe]

DO Not remove the head from that engine.
In most cases, removing the head will make it useless, never to run again.
I doubt you will find a head gasket for that motor as well, but, I've been wrong before.

 

[jimmbo]

That engine does not have a Cylinder Head to remove. Here is what you will find under the water jacket cover. This was my 1984 115hp

Specialty Tools? Ring compressors are one

 

[roscoe]

Aww jimmbo, no fun.
Yes Venomous Duck, there is no removable head.
You would have to cut it off, I mean in half.
You have to split the case open to access the innards.
And yes, #6 is often the first to go.

 

[racerone]

On some of the later inline 6 motors you may only need one of those ring compressors.------Rod bolts are different compared to earlier models.

 

[jimmbo]

They did switch from a Nut and Stud System to the One-Time-Torque Bolts in the early 80s, they also changed the Connecting Rod at the same time

 

[Venomous Duck]

Thanks guys. I havent even begun to look into tear down yet. Not what i was expecting but seems like a pretty simple design. I am waiting on the manual to decide if i want to tackle it. So where does the loss of compression occur, in the rings or at the powerhead? What is the risk of irreparable damage if I run it as is and start the rebuild in the fall?

 

[Chris1956]

Actually #3 cylinder seems to get damaged first. You probably need to bore oversize all cylinders that are low in compression, and install new OS pistons and rings. You must use new rod bolts, as they are one use only.
Any idea what caused the cylinder to be damaged? Likely overheat or lean mixture.

You only need a powerhead base gasket, but you probably want to replace the waterpump and clean the carbs as preventative maintenance. Check the upper and lower main bearings and replace orings/bearings if necessary. Don't lose the shims. Check the transfer covers for leaks,

Price the parts before you start, as things add up quickly. Unless you are really in love with that motor, you might price a newer motor.

 

[racerone]

Remove the 3 bypass covers on side of block and have a look at pistons / rings.----There are no gaskets that can cause loss of compression.-----Do not run this motor if there are compression issues !----Just finished assembling one of those motors.

 

[Venomous Duck]

Was planning on rebuilding the carbs while i had it tore apart. I am not sure what the cause was. I have had the boat for 6 years and it was getting used about 20-50 hrs a year. I started having trouble starting it, starter kept kicking. I replaced the starter with no luck so checked the compression and spark. Cod compression was in range, hot 6 was low. Spark gap test with new plugs in it was good. I dont recall the numbers of hand. It has never overheated that i know of while i have owned it, or at least no alarms. I run 50:1 premix, usually errored a little on the heavy side. I was suspecting it is just old and tired. I do know it came off of a early '80s ski boat so it was probably run hard. I have it on a '88 24' Aqua Patio that runs at about half throttle most of the time.

 

[Chris1956]

The starter kicking out is usually due to the motor trying to start unsuccessfully. One cylinder fires and Kicks out the starter. Make sure you are choking the heck out of her when she is cold. Cold start lever up, primer bulb pumped hard and hold choke button down until she fires.

It also helps to clean and rebuild the carbs occasionally. use new gaskets, inlet needle, seat and floats. The hard plastic floats can crack. the older foam floats can dissolve.