1973 135HP Where to start?

[taylor786]

Couple months ago picked up a ugly Johnson 77' 85 HP ran good until last week clutch dog went out I assume?.... It was running ok until then it would not shift into neutral or reverse stuck in forward...


Was shopping for a lower unit and found for sale a Johnson 73 135HP w/TNT. I checked the fluids and forward and reverse on the lower unit oil was clean and green and seemed liked a good lower unit and motor......The seller knew nothing about it except it was left there many years ago..... It visibly looked mint with a lil sun fading, I loaded it on the trailer for $260.
Got home swaped motors added fuel would not stay running at idle ....I do need to replace water pump and was going to do a carb job but....got the compression gauge and checked the cylinders
1.105 PSI
2.160 PSI
3.170 PSI
4.180 PSI

What should I do now? how much would a powerhead rebuild cost? I can do everything except cylinders and lower unit rebuilds! and advice would be great
Thank you! Long time forum reader first time post!
Hello Everyone!

 

[tx1961whaler]

Re: 1973 135HP Where to start?

First thing I would do is get another compression gauge and re-check. 160-180 psi is not a realistic measurement.

 

[Solittle]

Re: 1973 135HP Where to start?

Don't get your checkbook out just yet - - do what tx suggests - - if the results are similar it will be time to pull the heads for a look see - - take some pictures & post back with results.

 

[taylor786]

Re: 1973 135HP Where to start?

First thing I would do is get another compression gauge and re-check. 160-180 psi is not a realistic measurement.

Brand new gauge. On my 85 each cylinders check out at 100 to 110....kinda low but still runs ok, hard to start but does the job after the warmup.....

I thought those numbers where crazy off the chart from what little I know
...but that was after multiple rechecks before I grabed the paper to write them down, continually read the same on each cylinder

 

[emdsapmgr]

Re: 1973 135HP Where to start?

Those early 135's ran some pretty high compression. Normal on an overhauled would be 135+ on each cyl. An 85 engine would have compression in the 125 range. Before you tear into anyting, you may find that running some Bombardier Engine Tuner through the engine may cause the compression to come up somewhat. Follow the instructions on the can.

 

[taylor786]

Re: 1973 135HP Where to start?

I think first should be a carb job? Since it will not idle? Then miracle engine tuner hopefully for the cylinders? Then if that goes okay new water pump?
Heres some pics. Was told the lower unit is aftermarket cause there's no paint on it...

 

[emdsapmgr]

Re: 1973 135HP Where to start?

If the engine was sitting for an extended period, it may have some dried fuel gelatin in the carb bowls or the idle passages. A common problem Only way to clean them is to pull them apart and use a gas cleaner-like a Gumout type product. You won't have much luck using a fuel additive-it won't dissolve the dried fuel very well. Idle problems are usually related to a fuel restriction in the idle passages internal to the carb body-again-pull them apart and clean them well.

 

[taylor786]

Re: 1973 135HP Where to start?

Thanks for the help eveyone but. Im glad to say all my problems are from a blown headgasket! Pistons and cylinders look brand new! That was the reason to my crazy compression test readings!

 

[emdsapmgr]

Re: 1973 135HP Where to start?

That's so good luck-an easy fix! Make sure you run premium fuel in that engine if you run it at factory stock timing.

 

[taylor786]

Re: 1973 135HP Where to start?

After further observation... I found that the starboard cylinder head on the casting of the head the water hose port. Water flow was restricted by 60% beacause of excess metal on the opening during casting of the head improper Quality inspection lol
I redrilled the excess metal inside the port waiting.
Just killing time now cleaning bolts and waiting on the head gaskets,water jacket gaskets, carb kit rebuild, water pump rebuild, fuel lines and spark plugs.

 

[taylor786]

Re: 1973 135HP Where to start?

That's so good luck-an easy fix! Make sure you run premium fuel in that engine if you run it at factory stock timing.

I ordered a OMC 135ESL73M service manual arriving snail mail not here yet

Work done: New Head Gaskets and water gaskets both sides. Rebuilt carbs with new floats. New fuel pump, fuel lines, UL77V Plugs, Water pump rebuild kit. And soaked the pistons with seafoam and TCW3. Pistons and cylinder walls look great!

My questions are
1. Head bolt torque lbs?
2. Water cover/jacket torque lbs?
3. Timing advance specs at idle and recommended idle rpm's?
4. Timing advance at WOT and whats the max rpm's for this motor
5. Please show me where the tip and donation jar is located on this site for your help? I have been returning the help to other boaters like doin dishes

Thank you

 

[emdsapmgr]

Re: 1973 135HP Where to start?

A couple of additional PM tasks you should consider: Unless you know that the water pump impeller was recently replaced-probably a good thing to put at the top of your to do list. They deteriorate as much from age as hours of use. Why chance an overheat on your new engine. I'd also replace the vernatherm (thermostat.) No telling how old it is-it's good to know your engine is running at the correct temps under your ownership.

 

[taylor786]

Re: 1973 135HP Where to start?

A couple of additional PM tasks you should consider: Unless you know that the water pump impeller was recently replaced-probably a good thing to put at the top of your to do list. They deteriorate as much from age as hours of use. Why chance an overheat on your new engine. I'd also replace the vernatherm (thermostat.) No telling how old it is-it's good to know your engine is running at the correct temps under your ownership.

Absolutly Emdsapmgr water pump was on the list of work done....Did not do a Thermostat but I will asap! Can you bychance answer any of the 4 questions? Im still waiting on my service manual. Would like to knock the torque and timing out tomorrow.
Also I ordered UL77V Plugs...I thought those where gaped plugs at .030 but to my surprise there surface gap? Are UL77V's the right plugs?
Thank you Sir!