Merc 454 Alpha​ catastrophic failure - I have a few questions

Fuel pump failure.

I get not wanting raw fuel to dump into the bilge but what a piss poor design having it dump into the crankcase.
 
Yes, that is what happened.

Now to figure out a proper electric pump setup for the replacement engine and bypass this mechanical nonsense.
 
bergs said:
Fuel pump failure.

I get not wanting raw fuel to dump into the bilge but what a piss poor design having it dump into the crankcase.
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What??

Never heard of this. I have the exact same setup (454 w/Alpha) with 3500 hours and 500 hours since the rebuild. I hover around 40 psi all the time.

What happens when the fuel pump fails? How can gas get into the block?

I may just have to do an electric pump conversion to avoid this situation too...
 
From what I've learned, the mechanical fuel pumps for automotive applications have a weep hole in the pump body whereas the marine style does not. When the automotive style fails, fuel is dumped on to the ground. When the marine style fuel pump fails, the fuel dumps into the crankcase.

The way I see it, I'm either replacing the mechanical pump every season or I'm converting to an electric pump. Pretty sure I'll be researching electric pumps.
 
bergs said:
From what I've learned, the mechanical fuel pumps for automotive applications have a weep hole in the pump body whereas the marine style does not. When the automotive style fails, fuel is dumped on to the ground. When the marine style fuel pump fails, the fuel dumps into the crankcase.

The way I see it, I'm either replacing the mechanical pump every season or I'm converting to an electric pump. Pretty sure I'll be researching electric pumps.
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Thanks for the info. Sorry about the engine failure. That really blows!

I'll be keeping an eye on the fuel pump for sure!
 
bergs said:
From what I've learned, the mechanical fuel pumps for automotive applications have a weep hole in the pump body whereas the marine style does not. When the automotive style fails, fuel is dumped on to the ground. When the marine style fuel pump fails, the fuel dumps into the crankcase.

The way I see it, I'm either replacing the mechanical pump every season or I'm converting to an electric pump. Pretty sure I'll be researching electric pumps.
Click to expand...
Yes, this is my understanding too. You don't want the raw fuel in your bilge so it is designed to pump it into the crankcase.
 
i had a mechanical pump on my last boat with a volvo penta 3.0 . there is a diaphragm on the pump and if it fails you indeed flood the crankcase . nevertheless you should have a warning on your oil pressure gauge or not ?
 
In my case the gauge showed good pressure (40-43psi) since we were on plane for several minutes and turning 3000 to 3800 the entire time with the exception of the short visit to WOT. By the time I throttled down to inspect the engine compartment noises, the engine damage was already done. Yes, at idle is when I finally saw an issue with oil pressure. It didn't matter at that point since engine failure was obvious.
 
You would think they would have an external catch can or something rather than running raw fuel into the crank case. What a crap design...
 
boatman37 said:
Yes, this is my understanding too. You don't want the raw fuel in your bilge so it is designed to pump it into the crankcase.
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although the cost and time of replacing an engine does seem uncalled for I guess the Engineers had a decision to make....either allow the fuel to dump into the crankcase with a chance of ruining the engine or let the fuel dump into the bilge with a chance of blowing up the boat....tough call?

I would think there could have been some type of system design to protect the engine and the life of the boaters at the same time....

cliff
 
Why not flow it right back to the gas tank?
 
To be clear, if you have the overflow tube plumbed into the crankcase, that's not where it should go. It's a clear tube that goes to the carb. Your supposed to look at that tube to make sure it's dry. If you just dumped 2 gallons of fuel into the carb on 1 outing , you will notice that the engine aint running so good
 
@scoflaw : if i get it correct the pump is attached to the block and driven mechanically via a driveshaft and a mechanism which moves a butterfly on the pump up and down . if the sealing from this drive mechanism fails the pump indeed floods fuel into the crankcase. the overflow tube is for the membrane failing , not the driveshaft of the pump.
 
The pump is separated into 2 segments by a diaphragm. The rocker arm, which does the pumping , and air inlet, are on the dry side. The air inlet is connected by a clear tube to the carb. When the diaphragm fails the air inlet will fill with gas. If the rupture was that severe his engine would not have been able to hit top RPM's, which he said it did.

I'd suspect this issue had been going on for a while, and was a cumulative effect of many runs with a leaky fuel pump
 
you might be spot on the leaking was over a longer time because at a sudden massive fuelpump fail the engine would not run . a lesson to learn is surely to regurlary check the oil level and check if the oil looks and smells fine . i feel with him to blow an engine due to a 100 $ part .
 
As stated in post 6, the oil level was checked before the boat left the driveway.

Please don't draw conclusions from assumptions. I did everything correctly for my safety and maintenance checks. After a few hours on the water I went WOT for a short amount of time then kept an engine speed in the 3k rpm range until I heard the noises. In the moment I wasn't exactly thinking to shut the engine down and check oil level since I preferred to keep the boat moving and engine failure was unavoidable.


In other news, the engine was pulled yesterday. Looks like a con rod perforated the oil pan.
 
Some time in the 1990s mercury abandoned the block mounted fuel pump and incorporated the fuel pump with the raw water pump which is a belt driven assembly mounted to the motor. The diaphragm vent from the fuel pump is plumbed with a clear Tyron line to the carb so if the diaphragm breaks the fuel is diverted into the carb. Of course the engine runs poorly with excess fuel, but that is a good indicator that the fuel pump is dying. I also like that design because if the waterpump/fuel pump belt breaks and instead of your motor cooking it runs out of fuel saving it from over heating. You might look into upgrading your engine to this configuration. Sorry about your engine. Also make sure when you reinstall that you don't accidentally connect the remote oil filter lines in reverse. Some filters have a check valve to keep the oil from draining back into the block and so it won't pass oil at all through the filter if plumbed backwards. The pressures will look good at idle and low power because the oil will flow through the bypass in the block, but at higher power you will starve the engine of oil.

Good luck,

Pete
 
bergs said:
As stated in post 6, the oil level was checked before the boat left the driveway.

Please don't draw conclusions from assumptions. I did everything correctly for my safety and maintenance checks. After a few hours on the water I went WOT for a short amount of time then kept an engine speed in the 3k rpm range until I heard the noises. In the moment I wasn't exactly thinking to shut the engine down and check oil level since I preferred to keep the boat moving and engine failure was unavoidable.


In other news, the engine was pulled yesterday. Looks like a con rod perforated the oil pan.
Click to expand...

These things happen so don't be too hard on yourself.

I am curious because you mentioned that the Seller rebuilt the engine "last year". No one I know puts an old fuel pump back on a rebuilt engine. Even the cheap rebuilds get a new fuel pump because they always fail with age (although the vast majority fail due to ruptured diaphragms). I just raise the point because we just don't see a "fuel pump fail and flood the block" problem happen on CSR. In fact, in 10 years on this Board I have only heard of this happening one other time. It makes me wonder if the engine was rebuilt as the seller claimed.

It's unfortunate but you can take the steps now to ensure it never happens again.
 
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