BAM! Good day gone bad...

[pstew96]

So I'm fishing and actually catching! Then I decide to go closer to the lighthouse to fish, my boat is a Maxum 2400, engine only about 2years old, replaced the outdrive last year. I'm going about 24mph when sudden horrible noise, it sounded like the engine dislodged a bearing, very deep thumping and occasional slam, all I could see was a couple of strands of spiderwire line wrapped around my prop, I wouldn't imagine that would stop a 350hp 2 y/o engine. Besides, the engine sounds very bad even when disengaged of the outdrive, now I'm worried about engine damage, it does still go, just very noisily so I got towed back to dock. Any Ideas folks?

 

[j-d]

Please tell us the Year/Make/Model(s) of Engine and Outdrive.

Did the new Engine come with a new Coupler?

Is this Correct: You removed the Outdrive, and the Engine has the same Noise? Or... by "Disengaged" do you mean Out of Gear?

Whose Outdrive? We have an SEI drive that's noisy on a good day. Also had to ship the "upper" back to have its top bearings replaced under warranty.

I'm hoping some engine mount or accessory came loose.

 

[pstew96]

I would have assumed the new coupler would have come with a Mercury outdrive or would have come with the newish Mercrusier motor, second season, a EFI 350 Alpha. I meant disengaged as in not forward or reverse gear but still making weird noise, I would have thought it would stop in neutral. This is my second season with the new out drive, its a little over the warranty. Its a 2004 Maxum 2400 se, had a 5.0 in it but it sat after 60hours then popped a control arm after I put 40+ hours additional on it. Not having alot of luck with this boat.

 

[j-d]

If it's an Alpha Drive, it's all engaged right down the propeller shaft, even in Neutral. That's Flywheel, Coupler, Universal Joints, Gimbal Bearing, Upper Input Bearing, Upper Gears, Upper Output Bearing... Then in the Lower Half of the Gearcase (that comes off to service the Raw Water Impeller) has more Bearings and Gears. It's not till we put it in F or R, that the Shifter Dog engages the Forward or Reverse Gear (and both are always turning) and the Prop Shaft turns the Prop.
Did you get the 300HP 350? Multi-Port Injection? We recently replaced with the carbureted 275. Way more powerful than the pre-vortec EFI (throttle body) that came out. Back to you, 300 is the highest HP that MerC rates for Alpha Drives. And a 24 is a heavy boat.
Not telling you to do it yet, but I think if you pull the Outdrive, you'll find the noise comes from it.
Engine should include Flywheel and Coupler.
Did you happen to notice if Oil Pressure changed with the noise?
Did the noise change as you steered?
What's the Outdrive Brand?
Gear Ratio and Prop Specs?
WOT RPM and Speed?
Looking for something overloaded here...

 

[pstew96]

Yes the 350 Mag MPI Alpha plus 4800 - 5200 in a 4800lb boat, 1.47 Merc. outdrive. Only noise on engine running and in gear, able to move the boat but slowly out of channel but alot of various noises that would scare you to want to turn them off... oil ok....when I touched the risers they were exceedingly hot...

 

[j-d]

So you had an OVERHEAT as well as some mechanical failure...

Was this 350 engine new? Out of anther boat? Exhaust new or used?

Did you install the engine? The Outdrive? What about the Outer Transom Assembly?

I mention Transom Assembly because every shop told me they couldn't be sure how the job would go (and therefore cost!!) till they got the engine out and could inspect the boat's transom. In our case, the call was "Sea Ray Transom OK but MerC Transom Assembly shot." So for that extra price, "Reman" Engine and New Transom.

Do I have a point here? Yup. When we pull the Outdrive, the Transom Assembly stays. Same if we pull the Engine, Transom stays. Easy to forget there's about a foot of raw water hose incorporated into the Transom (also called Gimbal Bracket) to keep water flowing as we trim, tilt, and steer.

That 48-5200 is the RPM rating for the MPI. Is yours doing that RPM in your boat?

 

[jtybt15]

Sounds like a spun bearing and/or a broken rod. I think spun bearing, and if run on back to the dock, spun rod bearing will ruin crank.

Pull plugs. Broken rod will not have any compression...or air shooting out of the plug hole. Spun rod will have low compression. Air hose or looong screwdriver placed near each cylinder, you can hear any clunk.

 

[Gregory S]

When I read topic, I thought maybe you were fueling with the blower running again!