Momentary high rev's

[Crash]

Fleet Week here in the Bay Area so the gang all climbed aboard and motored out towards Alcatraz to watch the Blue Angels fly. Engine started up normally and idled without a hitch. Got out of the marina and into the estuary, no issues. I happened to be down below with a very cold one grinning ear to ear as the engine is performing so well after all I've gone through with her the past year. Temperature was a bit low so I readjusted the by-pass valve then we were at 120 degrees. Motoring for an hour the engine had a moment of high revs (nothing to be real concerned about as we just backed off the throttle at bit). I then noticed during the period of high revs our forward motion actually slowed considerably. We were motoring next to another boat and was ahead of them, but then fell behind them during this high rev period.

Once the high revs stopped (2-3 minutes) I throttled up to where we were and all was normal, including speed. Now this incident is bugging me as it does happen from time to time. Oh, in this case the high revs didn't happen again the rest of the day.

Sorry I don't have a tach to really be able to know at what rpm's I was at but I was going 3.8 kts. My prop was inspected about 3 weeks ago by my diver but this high rev incidence has happened before but didn't notice the loss in speed.

What do you guys think??
Thanks!

[Loki9]

Sounds like your prop is cavitating. Maybe it's time to scrape it?

[Ball Racing]

Forward clutch pack slipping?

[hanleyclifford]

Forward clutch pack slipping?

Agreed - turn drive gear adjuster in one notch only and test. See page 6-4 of the Moyer Marine Service and Overhaul Manual.

[thatch]

Slipping clutch pack

Crash,
The first time I experienced a slipping clutch pack, I was certain that my prop had fallen off. I was testing a prop with a more aggressive pitch and just overpowered the clutch adjustment. When the discs begin to slip, they will continue to slip until you throttle back and let things catch up. It is possible that you may have encountered some seaweed or that you just need a slight (one notch) adjustment.
Tom

[Crash]

Thanks for all your replies guys I knew I could count on yah all!

Loki: my slip neighbor (in addition to my diver) dove under to check and clean my prop and only reported I was missing a one of two zincs. I too thought my prop was loose or slipping.

Ball Racing: I hadn't of thought that!

Hanley & Ball Racing: Will read up on the adjustments and <scratch head> figure that out. I don't have the MMI manual BUT I do have the original Universal Motors Operation and Maintenance Manual (circa 1979).

Tom: Since I knew my prop was clean I spent the rest of the day thinking about this and just kept the throttle (I'll say) at half speed but never thought the slip might be from the clutch packing.

[Dave Neptune]

Detent

Crash, if you don't feel a definate click when going into forward it is definately the clutches. The A-4 should be a bit tough to get into forward as the cable poreassure locks the clutches in place with the detent.
It is very suprising just how well these A-4's do when not adjusted. I have heard many say they don't want to have to rebuild their trans because if they open her up she slips when 1 or two clicks an the adjuster fixes the problem~~not uncommon especially after a good tune up.

No worries, just be careful and go one notch at a time. Be sure you can see the adjuster with a mirror if need be. It is really not dificult. In fact it is more work reinstalling the cover plate.

Dave Neptune

[jpian0923]

How does she perform in reverse?

[JOHN COOKSON]

While You're Checking......

........Check the shift cable for proper adjustment. Is the outer cover being held firmly?

To test and adjust: Let the cable loose on the trany shift lever and shift by hand.

TRUE GRIT

[Crash]

Dave: Thanks for the insights, I plan to get into every part of this engine one day at a time....it's the first step that's scary!

jpian: reverse gear seems normal...moves backwards without any noticeable issues, not a lot of revving needs to be done to get the boat out but then again I'm slipped in weird spot where you want to go slow. I'm in front of the harbor master's office and the local yacht club and just gotta make sure no new "nickname" is added to the one I already sport.

John: will do, since I'll be on my belly stuck in a hole pulling cover plates off and cussing I'll check the shift lever while I'm at it.