Sputtering/Knocking and white Smoke, Oh No!

[Endorfins]

Last August I went to fire up the boat (1991 Euro f3 Mercruiser Bluewater DD) and it wouldnt fire, I ended up having to have the carb rebuilt. It had some stuck valves etc. Worked fine for fri and sat but on Sunday on the way in there was a loud knocking noise and my oil pressure dropped. I have no idea about where to start, I am not much of a mechanic but I do understand the mechanics of the motor. If anyone would or could help me, it would be GREATLY appreciated!

P.S. On a side note, if I do need to take it to a mechanic for diagnosis/repairs etc. Can anyone suggest someone in Mojave Valley AZ. Thanks

[98mallybu]

sounds like you might have sucked a valve or busted something on the lower end...

easy diagnostics

Pull off valve covers, look for missing/broken parts, if you can't see anything run a compression test on each cylinder and dig into thay cylinder more... if you dumped oil pressure you might have a lame motor

if that is the case... it will cost less money to replace than rebuild... you can purchase re-man motors through a mercruiser dealer... it's your best bet to make it drive like it did before and be reliable don't even think about a automotive motor, make sure it's marine... automotive motors don't run 4k RPM's with a 1:1 gear, you'll burn the motor up after 20 hours...

[Bill_AirJunky]

... automotive motors don't run 4k RPM's with a 1:1 gear, you'll burn the motor up after 20 hours...

I haven't heard of that before.

Years ago Spence at Bake's Marine rebuilt a Mustang 351 for my brother's Prostar 190. We never had any problems with it. Since it was an automotive engine, it rotated the opposite way of a marine motor. We had to install a Nautique prop on it to make it work, which I guess is a reverse pitch than what normally comes on an MC.

That boat ran the Catalina Ski Race a couple years ago & has 100s of hours on that engine now.

I'm not sure what Spence did to the motor to make it work, but we were of the understanding it was just a car engine with marine accessories, ie; alternator, starter, distributor, etc. But the internals were all car.

Anyway, Endorfins, I think I'd be doing a compression test on each cylinder. My guess is you will find one is drastically low.

Edited March 5, 2008 by Bill_AirJunky

[footnlongline]

... automotive motors don't run 4k RPM's with a 1:1 gear, you'll burn the motor up after 20 hours...

I haven't heard of that before.

Since it was an automotive engine, it rotated the opposite way of a marine motor.

PCM used Ford blocks in their Pro boss GT 40's for a number of years . Nautique and Hydrodyne put them in alot of boats, they had opposite rotation than Merc's or Indmars but were marine motors none the less.

[Marvin Gardens]

What do you guys think of Jasper engines for replacment (350)?

[footnlongline]

What do you guys think of Jasper engines for replacment (350)?

Most people think they are fine. My cousin had valve trouble with his, could have been a fluke though.

[Sixball]

Hope I am wrong but my firs thought is lower end Rod's. If you dump the oil and pull the oil filter check for metal. I would open the oil filter up and see what things look like. baring material? Is their water in the oil.

Oil pressure doesn't usually drop from top end unless it has progressed further. Things don't sound good you may want someone around who is mechanically sound.

Its