Hi,

I currently run a 496 Mag MPI, 375 hp over a Bravo 1, 1,5:1. 4 bladed 23p prop. 28 foot Smuggler classsic deep v, 25 degrees. Roughly 4000 lbs. Apart from high slip, I only reach 43 knots flat out at 4400 rpm, there is a slight rumble ( for lack of a better description) when I shift into gear. The noise is not instant, rather like it ramps up over a second or two as if the clutch slips a bit before fully engaging. Same fwd and rev.

Quiet out of gear, gimbal bearing totally smooth. Oil is fine, a very small amount of fine metal on the lower oil plug, deemed normal. No sound or rough/binding sensation when rotating the input shaft by hand.

This is way different from normal gear noise, sounds much rougher, almost crunching.

What can I look for, where? Upper or lower gears?

FredK,

Joined in 2009 and finally a post? Why so soon?

My first guess is you have gears eating themselves. Looks like some machining debris on the magnet. The delay you are seeing before the noise begins is evidence that there is debris in the sump that takes a second to make it up to your gears.

Speculating on my part, as I'm not a drive expert.

Thanks. Brad.

When was the oil last changed? You will always get a little fluff on the plug

First place id look is the shift cables, check your alignment between the two on the engine. Mercury factory manual says 6" or so, they make a tool to get exact

That delay is usually the cone clutch, not the pump.

UnderPSI,

My presumption was that it takes a second for the pump to pull the debris up to the gears, not that the pump takes a second to start pumping.

Thanks. Brad.

CheckmateScarabe,

I always get a little bit of powder when I pull my plug. Those look more like what I sweep off my shop floor after milling on a steel part. I wouldn't call that "fluff". I'd call them "chips".

Thanks. Brad.

Thanks for your ideas. I will open the upper to have a look at the gears. Oil was new this spring, only 10-15 hrs this season.

Picked up a carbed 502 last weekend, 450 hp+ is claimed. The 496 will be replaced for next season.


That is one of the reasons I need a drive I can rely on.

BTW, here is the boat, Smuggler 28, 1980. The C4 is a manual 88.


Gotta' love the 80s 😀

As an idot that has overpowered bravos and blown more than a dozen my guess is you have a broken thrust washer on the main gear stack making the gears sloppy. The cone clutch usually only slips in the direction of the most power aka forward. Thats why some people flip them over during a quick service. Get that thing apart before it makes tour tower a 2 piece unit! LOL Good Luck!

Has 43kts always veen you max speed and 4400rpm max? Or is it just with this current drive issue?

23p prop running 4400 is a bit more than I would prop it, certainly for a 28ft hull. A bit more rpm at 4800+ would be easier on the drive out of the hole and cruising/WOT.