Changed all our hoses about 3 years ago. 1985 36 aft. Job is labor intensive, need to pull and push with new hoses attatched to old thru tight quarters. At least two strong people needed to accomplish. It will be worth the effort. Recommend fresh water change over also as part of the job.
Wipe the hoses with a rag, then smell the rag. When I replaced all waste hoses on my boat, I used series 141, also called Tigerflex. Also change anti-siphoning loops at the same time, and hose clamps of course. Messy job, but wife will be happy, very happy
----warm moist rag. Take it out on the dock to smell. The test result is more "accurate" that way. The other bilge odors can disguise the head odor.
I replaced mine on a 92 3608. I found using a heat gun to warm up the new hoses made it much easier to manipulate them into position.