Hurth coupled to 454 Nercruiser

[tonyiiiafl]

I Hurth (maybe 630? Need to check) on my 1994 390CPMY coupled to 454 Merc Bluewater Gen V. Last couple days I have been getting a strange noise from that area. Sort of like a high pitched squeal (Not very loud, have to listen for it) between 850 and 1200 rpms. Nothing higher or lower. I checked the belts, sea water pump and found nothing out of ordinary. I saw there is a filter on the right side pf the transmission that unscrews and comes out. On the right is a dipstick that appears to have 90 weight gear lube. Fluid and filters changed every other year. It looked like the fluid was aerated and not clear when I pulled the filter. Is there gear lube on one side and ATF (Dexron II per manual). To change fluid, is it as simple as using a vacuum extractor pump and sucking out the fluid from the filter port and refilling? I would guess we are using Dexron IV or higher? Am I correct about the gear lube side? NO vibrations or shudders, truly smooth as can be> I was also thinking that the plastic cover on the flame arrestor could be flexing and causing the noise? Any ideas ?

[tonyiiiafl]

PS: I suspected Cutlass bearings, but they were replaced by the marine 2 years ago, less than 100 hours on them. Noise is more prominate from starboard, thats why I was thinking cutlass bearings.

[tomschauer]

Have you replaced or tightened the shaft packing lately?
Maybe it squeals a bit?

[Viper]

Tony what do you mean by "the gear lube side"?

The tranny should have Dexron ATF. Suck it out through the dipstick port and refill there. The filter can be cleaned and reused.

Unless it's obvious when a piece of hardware is squealing, a squeal in the engine bay can sometimes be a challenge to narrow down the source as the acoustics in the compartment can play tricks on you. It can be anything from something on the engine such as one of the pumps, alternator, belt, a pulley, or a tensioner. It could also be the packing gland, strut bearing, a misalignment, the fan in the charger if applicable, or something vibrating resulting in a squeal.

Does this happen both in gear and in neutral? Sounds like you're getting a squeal from both port and starboard sides? If so, shut down one engine and try to narrow down the general are of the squeal first to either the front or rear of the engine then go from there. Depending on what it is, a squeal can be generating heat, take an IR gun and point it to different components and compare the reading to the other engine. Shoot the shafts of pulleys and the hardware mentioned above and see if any raise a red flag. There's also the screwdriver trick or mechanic's stethoscope, just be careful. Make sure nothing else is running like the blowers, AC, etc.