$$$$ engine noise after prop strike $$$$

[the man]

Bro -in -law hit a rock, wasted the prop and skeg. 2005 4.3 Mercruiser with Bravo 3. He ran the boat back home with the half sized prop on it. He says it ran fine other than obvious performance reduction. I repaired the skeg and installed a new prop. Started it up- it idled fine for 10 seconds or so then loud noises and engine stall. Started it again- idled for may 5 seconds and then same thing. After a few wtf's. checking outdrive position and such I tried to start it again- loud noises. Sounds very metallic and severe, like gears grinding but stopping on impact.

Took it to my shop and removed the outdrive. Tried to start it with same result- loud noises. Will not start at all now. Ideas? Similar experiences? Related to prop strike? What to look for? Thanks...

 

[Joshua Nichols]

Re: $$$$ engine noise after prop strike $$$$

Took it to my shop and removed the outdrive. Tried to start it with same result- loud noises.

This alone has me leaning towards internal engine damage.. How? I am unsure of.. You would think other things would give first..Once ya get the engine out things will start to shine..I wanta say broken crank maybe? Seen em break on a 350 before.. Not from a prop strike ...anyhow. Keep us posted
Do like Micheal did in the "Godfather".. Kill the brother in law

 

[Bondo]

Re: $$$$ engine noise after prop strike $$$$

Ayuh,... 4.3ls have a funkily cut crankshaft,...

My guess is, yer's is Broken at a bearing journal...

 

[achris]

Re: $$$$ engine noise after prop strike $$$$

As a young man I was given a very sound piece of advise; "Never lend out your boat or your wife"... They both will come back the same... (Use your imagination)

 

[90stingray]

Re: $$$$ engine noise after prop strike $$$$

A 4.3 v6 with a bravo 3... seems like a weird combo. That sucks tho, just in time for summer to start I hope that is not the problem for you. I would have thought prop hub, sterndrive shafts & gears, coupler. I would have never thought a crank could be scrapped out after a prop strike.

 

[Don S]

Re: $$$$ engine noise after prop strike $$$$

The first thing to do is pull the spark plugs and inspect. If one looks like the picture below, you may have found your cylinder with the problem. If they look OK, do a compression test.

A 4.3 v6 with a bravo 3... seems like a weird combo.

Bravo 3 drives are quite common on the 4.3 MPI engines.

 

[Josh P]

Re: $$$$ engine noise after prop strike $$$$

It could have good compression if the crank is broke at a main journal. I saw an lt1 crank break on number 4 main jounal make a heck of a noise but was not missing.

 

[infideltarget]

Re: $$$$ engine noise after prop strike $$$$

Bro -in -law hit a rock, wasted the prop and skeg. 2005 4.3 Mercruiser with Bravo 3. He ran the boat back home with the half sized prop on it. He says it ran fine other than obvious performance reduction. I repaired the skeg and installed a new prop. Started it up- it idled fine for 10 seconds or so then loud noises and engine stall. Started it again- idled for may 5 seconds and then same thing. After a few wtf's. checking outdrive position and such I tried to start it again- loud noises. Sounds very metallic and severe, like gears grinding but stopping on impact.

Took it to my shop and removed the outdrive. Tried to start it with same result- loud noises. Will not start at all now. Ideas? Similar experiences? Related to prop strike? What to look for? Thanks...

Was this a stainless prop or aluminum? Did he run the engine at full power (WOT) after the strike (damage from extreme vibration)? Just trying to learn something here. I have busted props before, but only aluminum ones. I never ran the engine above idle to limp back to wherever. Never had any damage beyond the prop itself, and once a small chip in the skeg. NEVER would have thought the shock load would transfer all the way to the crank with enough force to break it. One would think SOMETHING between the prop and crank would have snapped first. The rubber prop hub immediately comes to mind...then any number of small gear teeth...clutches...SOMETHING.

 

[TilliamWe]

Re: $$$$ engine noise after prop strike $$$$

A 4.3 v6 with a bravo 3... seems like a weird combo...

Considering he said he replaced "the prop" I am guessing it's not a Bravo 3. He also mentioned getting it home with "the half sized prop". No such thing on a B3. Me thinks this is an Alpha and the man just doesn't realize it. The "only" way to get a 4.3 with a B3 is to have two of them in the boat.

 

[Don S]

Re: $$$$ engine noise after prop strike $$$$

The "only" way to get a 4.3 with a B3 is to have two of them in the boat.

I have seen and worked on 4.3 MPI engines with B3's, how can you say that?

http://www.mercurymarine.com/engines/inboards/sterndrives/bravothree.php

Nothing at all on the Merc site that says you can't have a B3 with a 4.3 without having twins.

 

[TilliamWe]

Re: $$$$ engine noise after prop strike $$$$

I can say that because VERY few runabouts cruisers have a 4.3 installed backed by a Bravo drive, period. Much more likely in a dual engine set up. How many 4.3 B3 single engine runabouts have you worked on? Less than twins in cruisers, I'll bet.

 

[achris]

Re: $$$$ engine noise after prop strike $$$$

I can say that because VERY few runabouts cruisers have a 4.3 installed backed by a Bravo drive, period......

Really!!! I've seen plenty of 4.3/Bravo III in boats about the same size as mine.... I was considering a BIII on my last re-power....

Chris.......

 

[TilliamWe]

Re: $$$$ engine noise after prop strike $$$$

Chris your boat is NOT a real "runabout". A B3 would be a decent choice behind a 4.3. Gang up with Don all you want. Bravo 3s behind single 4.3s are rare.

The original poster's BIL had a Bravo 3 and he "wasted the prop" as he says, the possibility of more damage is likely. Considering B3 props have no "hub" and are solid, if you "destroy" one, you almost certainly damage the propshaft. And if you destroy BOTH of them, you are in real trouble.

 

[the man]

Re: $$$$ engine noise after prop strike $$$$

Considering he said he replaced "the prop" I am guessing it's not a Bravo 3. He also mentioned getting it home with "the half sized prop". No such thing on a B3. Me thinks this is an Alpha and the man just doesn't realize it. The "only" way to get a 4.3 with a B3 is to have two of them in the boat.

I should end topic part of the thread with a correction. I have 4 boats and two of them have Bravo 3s, but not this one. I was incorrect when I typed that out in a hurry after a frustrating day. It had an alpha one that was replaced last year by a SEI 116. (that was after a "mobile marine mechanic" was remiss in filling it with lube.) Sorry for the bad info. The inside of the prop- I do not know the correct term- that has the plastic piece that would "shear" in this event did not shear. I assume that is why it is there but it stayed intact and allowed the prop to continue to spin. also. No he did not run the boat WOT, or at least he says he did not.
thanks for all the insight guys. as usual this site is invaluable- and humorous on occasion.

 

[Joshua Nichols]

Re: $$$$ engine noise after prop strike $$$$

As a young man I was given a very sound piece of advise; "Never lend out your boat or your wife"... They both will come back the same... (Use your imagination)

This goes for chainsaws also... Some people you can hand a rubber mallet and and a cannonball and at the end of the day they will have a pile of BBs...

OP after the engine pull let us know the outcome..

 

[the man]

Re: $$$$ engine noise after prop strike $$$$

Update: no broken parts, but did find water in port cylinders; thread here- http://forums.iboats.com/showthread.php?t=480023

Related? Who knows.