AQ131A Timing Problem????

I have a 1986 bayliner with an AQ131A/275. I bought it 2 years ago and the the compression was 175 to 180 on all 4 cylinders. This spring it wouldn't start and after trying many other things, a compression test showed 70 lbs on all 4 cylinders. I removed all of the accessories and can't find the timing mark on the valve cover. I have a Seloc Publications book, but the pictures appear to be from an older model (cam pully mark in the picture is a notch on the outside of the pulley, rather than a dot on the pulley like my boat). I am guessing from pictures I've found that I may be missings a guard that has the mark for the cam pulley? I found some pictures that make it look like I can line the crank and accessory pulleys up with their marks and use a string to line all 4 points of the center of the cam and crank pulleys and their timing marks. Does anybody know if that's right? Here the picture I found (thanks El Pescador):

http://www.threefattigers.com/Protocore/Volvo/TimingMarks.htm

Re: AQ131A Timing Problem????

There should be a plate with timing marks.The pully should have a notch that lines up with with the plate.All those marks(in pics) are for basic alignment.It will put you in the ball park,but you can be off 1 to 40 deg.Make sure the gears and pullies all are clean and rust free.
As far as your compression. Marvel Mystery Oil.Let it set for a day or 2.
Any Volvo dealer should be able to find that part.Probably VERY $$$$$$$.
There are a lot of salvage yards listed on the net.Jerry

Re: AQ131A Timing Problem????

Thanks. What salvage yard have you had luck with? I got the boat running the other day with the old pulleys, but they should be replaced.