76 Mercruiser 165 refresh recommendations

[calvinallen88]

Just got a free 1976 Arrow Glass with Mercruiser 165 from nice older couple. Running when parked but not started in at least 5 years. After getting home and soaking pistons with PB blaster for a day, I jumped started with screwdriver and motor turned over.

I have plans tomorrow to check compression, check spark, change oil, clean carb, etc.

Having never owned or worked on marine engines, anything else you would suggest for initial maintenance/inspection before getting to far into it? Thanks.

 

[kenny nunez]

Make sure there is no freeze damage.

 

[calvinallen88]

Make sure there is no freeze damage.

So once engine is running on muffs and hose, look closely for any cracks or leaks?

 

[kenny nunez]

Watch for any color change in the oil.
After you get it running and warmed up then check the compression. It is no different than an automobile engine basically. You will have to work over the cooling system.
Try to obtain a Mercruiser service manual.

 

[calvinallen88]

Watch for any color change in the oil.
After you get it running and warmed up then check the compression. It is no different than an automobile engine basically. You will have to work over the cooling system.
Try to obtain a Mercruiser service manual.

10-4. Luckily I got an original owners manual and full service manual along with the boat.

 

[Bondo]

Ayuh,..... Welcome Aboard,..... Is this the 165hp, I-6, or I-4 motor,..??..??

Hopefully, the I-6,.....

 

[Eric 3.7LX Alpha 1]

I'd also syphon some fuel out of the tank and inspect it before trying to fire it up. 5+ year old gas is going to have a tough time burning, and I personally wouldn't top off the tank with good stuff to make up for what's in the tank unless the old stuff smells like gas.

 

[calvinallen88]

Ayuh,..... Welcome Aboard,..... Is this the 165hp, I-6, or I-4 motor,..??..??

Hopefully, the I-6,.....

Yeah its an I6.

I'd also syphon some fuel out of the tank and inspect it before trying to fire it up. 5+ year old gas is going to have a tough time burning, and I personally wouldn't top off the tank with good stuff to make up for what's in the tank unless the old stuff smells like gas.

Yeah also planning to inspect fuel lines, flush fuel tank, and install inline filter. What fuel/treatment would be best to use? unleaded 87 ethanol?

 

[calvinallen88]

Yeah its an I6.

Yeah also planning to inspect fuel lines, flush fuel tank, and install inline filter. What fuel/treatment would be best to use? unleaded 87 ethanol?

Also, proper procedure for flushing water/coolant lines and exhaust? Would hooking hose and muffs up provide enough flush or do I need to unhook water pump lines and flush water passages from that end also?

 

[kenny nunez]

The flush out will give more than enough water. Using a bungee cord to secure the flush out to the drive is good insurance that it will not slip off while you inside the boat.

 

[calvinallen88]

So in boat now. Cleaned starter contacts and it is now turning over with key(but appear to have weak slave solenoid). Have cleaned points, checked coil(good). Confirmed spark.

 

[calvinallen88]

So when started yesterday had decent compression. Then after pouring gas in carb (I poured a little too much and fouled plugs, never got it started), and changing oil I have lost a lot of compression in all cylinders. Readings are about 60 in all cylinders. What would cause this? Head gasket? I still feel decent compression with finger test over SP holes.

I would love to see this thing idle for a few seconds on its own before I dive much further i.e. gaskets, head work, etc.

 

[Bondo]

So when started yesterday had decent compression. Then after pouring gas in carb (I poured a little too much and fouled plugs, never got it started), and changing oil I have lost a lot of compression in all cylinders. Readings are about 60 in all cylinders. What would cause this? Head gasket? I still feel decent compression with finger test over SP holes.

I would love to see this thing idle for a few seconds on its own before I dive much further i.e. gaskets, head work, etc.

Ayuh,.... So what was the "Decent" compression when ya started,..??

60 psi is a worn out core motor, not a runner,.....

 

[calvinallen88]

Ayuh,.... So what was the "Decent" compression when ya started,..??

60 psi is a worn out core motor, not a runner,...

Started around 145 psi. Then dropped to where its at now across all cylinders. Have I flushed all oil film from cylinders and from piston rings? Since I flooded it with gas and fouled plugs?

 

[Bondo]

Started around 145 psi. Then dropped to where its at now across all cylinders. Have I flushed all oil film from cylinders and from piston rings? Since I flooded it with gas and fouled plugs?

Ayuh,..... A couple cc's of oil in each cylinder, roll it over abit on the starter, 'n retest it,....

That seems like a drastic drop, to me,.....

Do a leak-down test, 'n listen to where the compression went,.....

 

[calvinallen88]

So I went and got a new marine batter (just in case the small car battery wasnt strong enough to last), cleaned all plugs again, checked spark on all wires, checked timing, added oil to top of pistons as suggested, rotated by hand A LOT to coat well, let it sit for almost an hour.

Then went to start and sounded weak even with new charged battery, and within 5 seconds engine seemed to seize again. Wouldnt turn by hand or starter so PB blasted it and let sit for a few hours.

Had pretty much given up on avoiding removing the head before hearing it run so started tear down. Removed rocker cover and intake/exhaust manifold. Some of the rocker arms are loose and can twist them sideways off of the rods...I assume this is not within specs?

Before I went any further I decided to hit the key and the motor spun again. So decided that before I removed head I would hit some starting fuel to intake holes and it fired off. Same after spraying some actual gas onto cylinders.

So now my next question is the starter weak? Even with new battery still seemed to struggle. I have already cleaned all connections to starter/solenoid etc. How hard would it be to tear down and clean the starter?

 

[GSPLures]

So I went and got a new marine batter (just in case the small car battery wasnt strong enough to last), cleaned all plugs again, checked spark on all wires, checked timing, added oil to top of pistons as suggested, rotated by hand A LOT to coat well, let it sit for almost an hour.

Then went to start and sounded weak even with new charged battery, and within 5 seconds engine seemed to seize again. Wouldnt turn by hand or starter so PB blasted it and let sit for a few hours.

Had pretty much given up on avoiding removing the head before hearing it run so started tear down. Removed rocker cover and intake/exhaust manifold. Some of the rocker arms are loose and can twist them sideways off of the rods...I assume this is not within specs?

Before I went any further I decided to hit the key and the motor spun again. So decided that before I removed head I would hit some starting fuel to intake holes and it fired off. Same after spraying some actual gas onto cylinders.

So now my next question is the starter weak? Even with new battery still seemed to struggle. I have already cleaned all connections to starter/solenoid etc. How hard would it be to tear down and clean the starter?

It would be easier to pull the starter and have it tested (auto store should do it free). That will let you know without much effort or money if it is the starter. If it is bad possibly find a rebuild shop that can do marine starters or buy a new one.

 

[calvinallen88]

It would be easier to pull the starter and have it tested (auto store should do it free). That will let you know without much effort or money if it is the starter. If it is bad possibly find a rebuild shop that can do marine starters or buy a new one.

Ok thanks. In the morning I plan to pull and clean the starter contacts and brushes and make sure there isnt anything obvious causing problems, then reinstall and test again.

If I can get it starting semi reliably I probably will throw the manifold back on and test again squirting gas into carb before I remove carb and clean.

 

[calvinallen88]

UPDATE:
Removed and cleaned starter last night, cleaned mating surfaces and reinstalled manifold, checked fuel pump (working). It now starts up through carb everytime but dies as soon as I let off key. Weak ignition coil? Since when let off the key voltage to coil would drop then coil would not be able to operate at lower voltage? I have confirmed 5v power to coil when key is in run position. Is this enough?