AQ170C Compression readings. Your thoughts please!?

[boatingmark]

Hi all.

Do I have trouble on my hands with these readings?

1- 125
2- 150
3- 120
4- 120
5- 155
6- 150

Although not extremely low its the difference between them that I question.

Thanks in advance

 

[boatingmark]

Just want to add, i did this test allowing 5 puffs but realised when i got home some people suggest to also have the throttle wide open?

Question is did i need to?

 

[Scott Danforth]

spray some oil into the low cylinders, see if they come up. if they do, its ring related. if they dont, its valve seat related. could just need to pull the heads to clean up the valves.

any chance this is a salt water boat? when was the last time the manifolds were inspected?

 

[boatingmark]

Thanks for the reply scott!

Ok, yes ill give that a go, im assuming you mean just the ones that are reading the lowest? Do i spray each one individually then instantly check the compression on that cylinder?

Can i run my boat with the readings the way they are? Im pretty sure nothing much has changed from last year when i used it, although running rich i seemed to have enough power to explore these narrow rivers here, i barely go over tick over, the speed limit here is 7 mph (big engine for this application!)

Possible the valves could be mucky then? The engine has been running rich for sometime causing sooty build up on plugs on a regular basis, can this effect the valves?

Its been in fresh water for at least 5 years, ive owned it 2 years.
The exhaust manifold looks ok, Ive had the water pump rebuilt, rebuilt the sea water pump as it was leaking slightly. new plugs, new leads, oil and filter, new starter. new alternator, Ive rebuilt the cooling system and installed a venus water filter. Installed a venus fuel filter/water separator. Cleaned and inspected oil cooler.

Next on the list is a carb rebuild (kits on order), recently had trouble with starting, ruled out fuel pressure but i do have a weak spark, later today im installing a new coil and readjusting points. Cranks but doesnt sound like it fires.

I need to start posting up pics, going to try and revive my photo bucket account!

thanks
Mark

 

[jerryjerry05]

The throttle doesn't need to be open all the way.
​All the plugs need to be out.
Pull the coil wire if using the key.
Turn the motor over until the gauge stops going up, that could be 3 revs or 10???
Spray oil after the test.
That will tell if you need anything fixed??
The readings could be the gauge? or the way it's done?
This kind of motor, the comp readings can be off and the motor still runs.
My outboard 3cyl. if the comp is off by too much it doesn't run right if at all.

Possible the valves need adjusting? But I'm not sure they can be adjusted??

 

[boatingmark]

thanks Jerry

Thats good about the throttle although i didnt have it open at all.
I had pulled all plugs and disconnected the ignition system.
I found that compression wasnt increasing after the 4th to 5th puff but i will try again to double check this.
i hope its not the gauge as its brand new! I guess i need to use another gauge to compare results.

Yes maybe valve clearances?

Sounds like i have a few other things to check out on top of everything else, this boat will be the death of me lol :facepalm:

 

[Scott Danforth]

It will run with those numbers. However why are a few low. Regarding manifolds, unless you separate the riders from manifolds, you can't tell from looking at the outside

 

[boatingmark]

Thanks Scott

I had a break through this weekend and got to use the boat!

I cleaned up and old points and put them back, left the new condenser on and it fired up no probs.
I did struggle to adjust the timing due to not being able to see any marks on the pulley wheel to work with, I adjusted it the best I could by ear at idle and increased RPM.
I then installed the electronic ignition and a new coil, readjusted timing then used a gunson colour tune kit to adjust the air and fuel mixture and I have to say its never ran so well before!!!

It did feel like I was running out of adjustment on air screw, I wonder if this is because the carbs need overhauling. Im going to balance the carbs next then repeat the air and fuel tuning process. Possibly another oil and filter change as it does look pretty black!

I ran the engine for 5 hours and it didn't miss a beat, it wasn't as smokey and smelt less of fuel, only problem I had was the outdrive unclipped a few times while reversing which is a pain, perhaps the clip is too worn to hold it in place now.

I will still carry out the test mentioned above tipping oil into each cylinder and recheck the compression, if it looks to be valves I hope its not too much of a job to correct!?

Thanks
Mark

 

[PiratePast40]

For the outdrive flipping up in reverse, first adjust lift linkage and shift mechanisms according to the manual. If that doesn't work then the pawls may be worn and need replacement.

A compression test is a better indicator when the engine is warm. If you've run it for a few hours, you may have gotten some of the rust of the cylinder walls and getting the rings to seal better now. Keep in mind, with that old engine, even if you have a few low cylinders, it'll still run. If you're not going offshore and need absolute reliability, I'd think twice about pulling that engine apart. Take a look at the price of a replacement exhaust manifold and you may come to the conclusion that treating it with some TLC for the next couple of yeas is a much less costly alternative.

 

[boatingmark]

Thanks for the reply Pirate!

Unfortunately Ill have to wait until i next pull the boat to have a go at adjusting the shift mechanism you refer to. Its a right pain when it unclips, then clunks back in!

Ill be sure to do another compression test on a warm engine then thanks.

Yes, i think your right although would checking/cleaning up the valves be a big job if that's whats giving the lower compression readings?

I realize parts are expensive and hard to come by for these old engines however as long as i have a pattern to work with i could get parts fabricated at work as a last resort, im a CNC Miller by trade and we have a fabrication unit as well as turning and milling capabilities.

Thanks
Mark

 

[PiratePast40]

For the adjustment, it's not just the shift mechanism, there are important settings on the lift mechanism as well. The description in the manual is pretty straight forward.

When that outdrive pops up, it's also manipulating the u-joints at an extreme angle. Keep the RPM's down to avoid damage.

A valve job involves machining the valves and seats to specific angles. What I was really getting at is that if it's running well, and you don't have unlimited funds or time to mess with it, enjoy the boat. Removing the head, and especially the associated manifolds and cooling lines, is a pain. Especially with that long cast iron behemoth you have. There are plenty of maintenance chores on a boat that need to be done before going after something that may just be due to the age of the engine and not a big deal. Some of us have fallen into the trap of "if it ain't broke, fix it till it is" trap. Perhaps you do have a bad head gasket or need a valve job but I wouldn't go looking for trouble. The up side from the numbers you're showing is that the number 6 cylinder looks good. I'd run it the way it is and have fun.

 

[bruceb58]

Did you use a dwell meter to adjust the points? Those motors are very sensitive to dwell and you need a meter to set them exactly on. Check the timing once you set the dwell.

I agree that you need to do the compression test when the engine is warm. Make sure the throttle is open, all spark plugs are removed and the ignition is disabled.

 

[boatingmark]

Thanks Pirate, ive had a good look at the manual and im struggling to find the adjustments you refer to. I can only see the instructions on dismantling and assembling the retaining pawl, aside from a shift adjustment it looks like it just operates using springs!?

To make matters worse my lift isnt working properly and hasnt for sometime, the motor sounds when using the switch but nothing happens, last time i pulled the boat i checked to make sure the rod that comes up from the retaining pawl wasnt sitting against the bottom of the lift mechanism, the outdrive has come up before in the past but now it seems like its every time i engage reverse.
Whilst i had the boat out i wish i had removed the top hat shaped disc the moves down into the rod to unlock the outdrive, i realised you can only remove the lift assembly inside the boat with this removed!! I could of checked over the worm gear etc.

​I dont suppose theres a quick fix without pulling the boat? Bearing in mind i cant currently use the lift anyway could i permanently fix it in the down position in the water?

I agree and understand what you say about the engine, i really dont want to be constantly working and not enjoying it, please can you explain why its a good thing number 6 cylinder looks good?


Thanks
Mark

 

[boatingmark]

Did you use a dwell meter to adjust the points? Those motors are very sensitive to dwell and you need a meter to set them exactly on. Check the timing once you set the dwell.

I agree that you need to do the compression test when the engine is warm. Make sure the throttle is open, all spark plugs are removed and the ignition is disabled.

Thanks for the reply Bruce. I have installed electronic ignition now, the engine starts and runs much better.

Ill be sure to warm up the engine and retest the compression!

 

[captmello]

This is not true.

i realised you can only remove the lift assembly inside the boat with this removed!!

However the boat may sink if you pull the lift while in the water.

 

[PiratePast40]

Can't seem to get the page to print, but the adjustment is on page 127 of the manual.

There is another thread here about the lift motor. The important thing is to first make sure all the connections are clean. It could very well be something more complex, but go after the simple, and cheap, fixes first.

 

[boatingmark]

This is not true.



However the boat may sink if you pull the lift while in the water.

Isnt the top hat shaped nut larger in diameter than the hole running through the transom?

The manual recommends removing this nut and a washer first?

Please can you tell me how to pull it out then, mine seems solid, even after removing some of the top assembly i couldnt get any movement, like i mentioned before the motor sounds but theres no movement, if i remember correctly i checked the small gear that runs from the motor to the larger worm gear and that was connected.
I removed the bolts that hold the housing to the transom and it wouldnt budge, couldnt even spin it slightly.

The lift worked for a short while after i purchased the boat then suddenly stopped.

Thanks
Mark

 

[boatingmark]

Thanks Pirate i can see instructions now, doesn't look too bad however seems the boat will need pulling in order to adjust!

Then you have to hope and pray when its put back you've done it right!


Did you mention there was a thread here on the forum about the lift motor or did you mean the manual? Ive seen page 130 regarding reconditioning but there's barely anything on troubleshooting.

Thanks
Mark

 

[captmello]

Isnt the top hat shaped nut larger in diameter than the hole running through the transom?

The manual recommends removing this nut and a washer first?

Please can you tell me how to pull it out then, mine seems solid, even after removing some of the top assembly i couldnt get any movement, like i mentioned before the motor sounds but theres no movement, if i remember correctly i checked the small gear that runs from the motor to the larger worm gear and that was connected.
I removed the bolts that hold the housing to the transom and it wouldnt budge, couldnt even spin it slightly.

The lift worked for a short while after i purchased the boat then suddenly stopped.

Thanks
Mark

I did not see that in the manual...Its been a few years since I went through mine, but I'm pretty sure the unit will come out all together. Maybe someone can correct me. I believe I put a pipe wrench over a rag and was able to get the unit to turn and loosen up. It will be stuck in by corrosion and crud built up, but once out and cleaned up it goes in and out easily. The other thing to do is get a piece of wood between the outdrive and the foot of the tilt from behind the boat and use the outdrives weight to put some pressure on the tilt while you try to turn it from in the boat.

 

[boatingmark]

Thanks for your reply captmello

After looking again, it may just be the instructions to recondition the unit, its listed as removing components in an order. Perhaps this doesn't mean the unit wont pull out as one though.
Ive found a small pipe wrench so im going to see if I can free it up this weekend, more so hopefully work out why the motors working but theres no movement from lift. Limit switch seems to work, but would the relays cause this issue? If it were the replays it wouldn't work at all would it?

Anyone have anymore ideas on preventing the drive from unclipping on reverse apart from the adjustments? I guess im hoping for a quick fix rather than pulling the boat but being realistic there probably isn't one!?

thanks
Mark