350 mpi screeching on startup

xpornsta 05-29-2003, 9:27 PM

hey
ive got a 350 mpi towsports mercruiser v-drive and when i start it, there is a screeching noise someone said this could be the belt slipping, would this be correct or is it comething else?
the engine has about 40hrs on it

thanks

(barry) · (barry) **Join Date: Apr 2002** 05-29-2003, 9:47 PM

Yeah, it's probably a belt.. mine did the same thing at about 40 hours.

B-

bigd 05-30-2003, 6:06 AM

When I changed my impeller we didn't tighten the belt enough the first time we started it up. It screeches like a mother. Just get in there and crank it a bit & it should be OK.

(trash) · (trash) **Join Date: Jul 2001** 05-30-2003, 7:41 AM

That's what happened to mine this year. When it screeches open up the drive box and look. On mine the only thing turning was the crank pulley. Good thing I didn't go out with it like that! Forgot to bring tools on the boat....

Oh yeah, mine is a 350 MAG towsports as well.

Trash

swpmwinc 05-30-2003, 7:58 AM

Had the same problem with mine the belt tensioner was out of adjustment fixed that no problem since

wes_the_gimp 05-30-2003, 8:42 PM

no noise but it seems to take a while to start up. about twice as long as the truck. is this normal? thanks

matt_dettman 05-30-2003, 10:02 PM

Steve,

If the belt is tight, you probably grenaded your impeller. I know, with just forty hours it may seem unlikely but it's probably the case. Release the tension on the serpentine belt then try to turn the water pump pulley by hand. It should NOT turn in one direction and turn with significant drag in the other direction. If you can't turn it either way, the impeller has shed some vanes and they are stacked up on each other causing the pump to lock up which in turn is making that God-awful squeal we all know and love...

Matt

(Message edited by matt_dettman on May 30, 2003)

(peter_c) · (peter_c) **Join Date: Sep 2001** 05-30-2003, 10:08 PM

Wes, that is not normal. Could be something like a fuel pump check valve???? It is under warranty right?

(ocrider) · (ocrider) **Join Date: Dec 2001** 05-31-2003, 12:09 AM

Steve,

I second Matt's assessment. I had the same problem one time when for some foolish reason we decided to jumpstart the boat on the ramp since the battery was dead. As soon as the hot impeller hit the cold water, it exploded and locked up. The screeching was the belt slipping across the pulley because it completely froze up.

Just last week we got into my buddy's boat and sure enough the impeller went out (at 200+ hours) and it started screeching.

If I were you I could get the impeller changed ASAP and don't keep turning the engine over or else you might risk damaging the entire water pump and paying $400 instead of $40 to fix it.

Ryan

krug 05-31-2003, 8:07 AM

i DID THAT JUMP START BS ONCE, NOT GOOD, now i just drive the truck down into the water!

xpornsta 05-31-2003, 2:53 PM

thanks guys
i will try checking that out. so if the water pump pullry turns fairly easily does that mean my impeller is shot?

matt_dettman 05-31-2003, 4:34 PM

Pretty rare for the pulley to free-wheel due to the impeller vanes being all jacked up in the pump housing. Just remove the pump by taking off the two 9/16ths headed bolts on the pump bracket and removing the two hoses. REMEMBER which hose is the input so you don't switch 'em when you reassemble!. DO NOT attempt to take all the 1/2" nuts and bolts off the housing until you get it up on the bench. You will see what I mean when you take it off...

Also. Reassemble all the broken vanes and sort of put the puzzle together on the bench. Some of the broken parts will probably be down the output hose up against the transmission cooler. You can back flush them from the other side or dig them out with a grabber tool thingy...Enjoy!

Matt

wes_the_gimp 06-06-2003, 6:04 PM

Pete, yes its still under warranty. just had the 20 hr. they didnt seem to think anything was wrong. she starts every time, just have to keep the starter engaged long enough.

silverram 06-07-2003, 7:08 AM

Get some belt dressing. It is liquid grip you can spray on the belt. If it only slips at startup it probably already feels tight. You can buy it at most auto parts stores.

(magic) · (magic) **Join Date: Mar 2002** 06-07-2003, 6:16 PM

I would have to say, just say no to belt dress. Use some wax instead (sold stick kind). I have the same motor and the belt squeks a little bit some times at low idle.

I just use dry suit zipper wax that I have in the boat anyways. Works great and does not leave a mess like dressing.

sandman 06-07-2003, 9:00 PM

I have a Black Scorpion and it does the same thing if it rev it a little within the first 10-15 minutes after it is running. I have tried the belt dressing and it works for a few days but then it just starts squeaking again. Kind of annoying. I may give this wax a try. Where can you purchase it at??

(monstertower) · (monstertower) **Join Date: Mar 2003** 06-07-2003, 9:32 PM

A quick and dirty "ghetto" way to quiet down belts is a bar of soap run over the belts. If it's just the belts this is fine but if it's the impeller as discussed above hiding this may be a bad idea.

My $0.02