DF250 timing chain noise, bad tensioner?

[DiverDave]

First let me say that I am an experienced automotive and marine mechanic, but not trained on all aspects of the four strokes. I have owned and worked on two DF140s and one DF50, and purchased a used 2004 DF250 a few months ago. I got it running easily and it has good compression, but there was a "sewing machine" noise coming from below the powerhead. I am fully aware of the timing chains, and variable valve timing system on these motors, but know they are generally almost silent, so the noise was an obvious problem. I did some research online and only once or twice read where anyone had experienced a bad tensioner or worn out guide. The motor has 800 hours on it and is very clean, and the oil was fresh and the oil pressure is correct. I first pulled the lower off and ran the motor to rule out noise traveling up through the mid section, then pulled the valve covers and checked the lash which is perfect, after which I installed new OCV gaskets hoping it was something simple like lack of oil pressure to the variable valve timing system, but noise was still there.
Well I let it sit for a long time but recently decided to mount it on the hull I bought it for and then ran it some more, but the noise is still there of course. Well I had the spare time this past weekend to pull the powerhead off, and low and behold the chains are loose in several places.
The tensioner on the main chain when levered slightly moves freely in and out, and when I exert pressure on the guide it seems to tighten up the main chain and also moves the cam chains so that they are tight, so I suspect it is the culprit. My question is two fold, first does this tensioner have any anti-loosening engineering (most car timing belt tensioners do not loosen when oil pressure drops) second should I inspect/change all of the hydraulic tensioners just to be safe so that I do not have to pull the power head again. And BTW I will be installing a new the bottom shaft seal and any other gaskets and o-rings when it goes back together.

[redlowrey]

I would have thought you would have checked the oil pressure seeing it plays an important role with variable valve timing. As far as the tentioners go just have a look you will see the ratchet on the plunger as it comes out of the body, I would think they would be a ratchet type of tentioner. I know without a scan tool you would not know how well the variable valve timing was working so there is a question mark there. It all depends on how much you want to spend,