penta aq125 would not start!

[2stroke1971]

Re: penta aq125 would not start!

Don, Ive never seen this one run... Not sure how it did before. Thanks for the diagram, Ive not found one like that so far.
And just to double check, number one cylinder is the one towards the front of the boat, right? Right next to the cam timing belt pulley

Right, TDC on #1...I lined up the crank mark and even pulled the valve cover to double check, both lobes all the way up and off the "lifters" even though they push instead of lift...lol reminds me of my old Geo Metro, it had an overhead cam design like that. Broke a few of those "lifters" on that thing!

There is a procedure for placing the distributor in the shop manual I downloaded...its a little fuzzy, one step says get the rotor 60 degrees from the line on the dist, the next step is to place the dist, and make sure the lines are opposite...um that would be 180, not 60.

Im gonna double check the wire order against the diagram above, and go from there.

Thanks again guys. At least by the time Im done, I might be able to help some others!

 

[Don S]

Re: penta aq125 would not start!

Do you have a link to the manual that you downloaded?

 

[captmello]

Re: penta aq125 would not start!

Can you confirm the crankshaft and cylinder #1 were on the compression stroke when you installed the timing belt?

If you have a compression tester, that may tell us something.

 

[2stroke1971]

Re: penta aq125 would not start!

Double checked the plug wires, labeled each end with a sharpie. They were correct.

I put a timing light on, cranked it with all plugs out. It was showing 30 degrees BTDC. Adjusted it so it was about 6 degrees BTDC at least at cranking.

Rolled the crank around until the mark was on zero, the cam notch lined up with the valve cover. The lobes for number one were up and out of the way.

Put the plugs in, and cranked it, and nothing, then kaboom. another backfire.

A kind neighbor lent me a compression tester.
Number 1,2,and 3 all registered 150 pounds after 4 or 5 revolutions. NUmber 4 read ZERO, didnt even bounce the needle.

Is the AQ125 an interference motor? That is, if the timing skips can the pistons crash the valves?

Hoping I can get away with replacing a valve.

Just bothers me. The previous owner said it ran at the end of last season. Shame on me for not hearing it run. Two weeks ago I met him for some paper work, and he said again, "right before we took it out, I started it up and ran it up and down, got right up on plane and ran great." .

 

[2stroke1971]

Re: penta aq125 would not start!

Pulled the head just now.

Number 4 exhaust vavle...at least.
Its burnt, edges broke away on one side. The piston got dinged up a tad....nothing I cant smooth out and run I think. From the pieces of the crumbling valve I imagine.

Other pistons look fantastic. Some carbon, but not bad.

So, now to replace the valve....not sure about the intake on #4...have to brush them all off tomorrow and see whats what.

Good lord.
EDIT: The intake valve for #4 also does not hold water so to speak, not sealed well. The exhaust port on #$ is a little disturbing, its like some material has melted away, or corroded away so that the opening is not regular like the other three ports. It was running hot I guess.

The seawater system was leaky and all,probably sucking air because of the bad seal on the pump at least... but now Im wondering about the heat exchanger and all of that.

Dont know which way to go on the head. Money is a bit of an issue. If i wait to have it "rebuilt" that will put me down for weeks. Dunno what to do.

 

[2stroke1971]

Re: penta aq125 would not start!

Just venting at this point.
All the exhaust valves were bad, the three that hadnt disintegrated were on the verge of doing so. Cracks thru.
Exhaust port #4 was eroded away, a very thin gasket surface left. I was able to build it back up with a welder and cut a new surface. Not what it should be, but better then it was.
Lapped the intake valves and put them back in, they all seal up nice now.

Thats it for a while. $140 worth of valves, about $125 in gaskets to go at this point. Dont sound like much, but Im a working man, and work is slow.

Hope to god the bottom end is ok.

I take it this thing had a severe oveheating issue, which leads me to make sure Ive got that licked before running it, whenever that may be.

Ive rebuilt the seawater pump, Ive got new seals for the plumbing. I know the seawater pump was a mess, blown seal, bad bushing, bad cross piece, etc....I think I should check out the engine water pump since its staring me in the face right now. A little scared to try those bolts, they look nasty. The engine pump feels ok as far as the bearing, but I guess I should pull it to check the condition of the impeller.

The heat exchanger is off at this point like most of the engine parts. What can I do to service that? Is there any good way to clean it out? Are there lots of chambers in there or what? Im not even clear on how this cooling system works as a whole.... got to get my head around that so I can be darn sure Ive taken care of the things that got this thing all messed up to begin with.

In any case, I think I better break out the bridge cart. Having sold my old boat a few weeks back, it looks like my first few trips this year will be down a bridge or pier.

Sorry to ramble on, its good to clear my head.

 

[captmello]

Re: penta aq125 would not start!

Glad to hear you're fighting through it. I did a valve job on my motor when I first bought it as well. Like you said,

Oh well, by the time I get this thing on the water, at least I will have made friends with the engine!

True words.

How do the cylinder walls look?

I believe you found the overheating problem in the pump coupler. The heat exchange is like a radiator, In your case, the antifreeze is to the inside and the raw water flows from your raw water pump, over the Heat exchanger, through the exhaust manifold and out. The block is cooled by the antifreeze which is good as it is anti corrosive.

You could talk to a radiator shop about checking out the heat exchanger if you think its bad.

Let us know how it goes.

 

[bruceb58]

Re: penta aq125 would not start!

Since this thing probably overheated, did you have the head resurfaced? Might be a good idea since it is an aluminum head.

 

[2stroke1971]

Re: penta aq125 would not start!

Ordered the 4 valves, they will be in on Tuesday. I am lucky to have found a volvo dealer thats been around a while. He has some old stuff in stock, and I pick his brain. Every time I buy a part, we talk shop, and its great. Between this board and my dealer guy, Im feeling pretty good about my chances!

Anyway, I took a pic of the container that was involved in my last backfire. The outdrive was dipped into this, and Kaboom! It blew a hole right through the container, roughly in the shape of the exhaust port! Too cool! One of my poor sons was standing right back there!

I am tentatively planning a test run next weekend...I spent the last few days getting the tow van ready, hitch, and lights on the trailer, etc...
I think Im going fishing today from a bridge because the weathers so nice, and Im down until the valves come in!

Thanks again everyone!