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HyperDonzi
08-20-2002, 02:37 PM
we have a 4.3l mercury in the baja, 19" pitch, would hit 5200rpm at the beginning of the year now only hits 4500 at wot. now, my question is, we were heading back, 3800 rpms (cruising speed) and before one of the bridges, I pull over and do a few donuts, to make sure the others are scared when it just seemed to loose power, i thought maybe i cavitaed it a litte, so i went strait and i only hit 4000rpm temp was 250, normally 160, so i idled to the bridge and on the way back i didnt go above 3500rpm, keeping the temp low exeept for 10 seconds, floored to see how high the rpms go (4500). the propblem is gone, was it just an overheat?

Moody Blu'
08-20-2002, 02:41 PM
soudns like it, maybe the donuts stopped the drive from sucking water due to cavitation?

Digger
08-20-2002, 02:58 PM
sounds like you have something a little more significant going on if the engine will not produce full turns. try to detail here as much info as you can and the varsity level motorheads will be able to help you, i.e. hrs on engine? maintenance history? any significant problems in the past? what is the oil pressure? last fuel filter change? etc etc.

p.s. for starters, I think we need to adjust your caffeine intake. how many Jolt sodas do you drink every day? :D

Moody Blu'
08-20-2002, 03:30 PM
I guess im not varsity ,thanks for the dig digger frown

Gary S.
08-20-2002, 04:32 PM
Do you leave it in the water ??? If so my reply would be a dirty bottom and junk growing on her.

Mustang Susie
08-20-2002, 06:30 PM
Hey Hyperbaja,
just gotta say... love the new avatar :p :p

P.S. perhaps I could send you a prescription for some ritalin? :confused:

Mustang 'I wish I had that much energy' Susie

mattyboy
08-20-2002, 07:53 PM
may be it's pubity :D eek! wink :p
sorry could'nt resist.
Digger's right could be a whole lot of stuff going on down there. if the impellor went dry for only a moment it could be fried and will only cool under way, or maybe even worse.
your probably to young to remember Dragnet.

Just the facts mame!

post all the symptoms and the answers will come

Matt

HyperDonzi
08-20-2002, 08:40 PM
all stock hours probably around 1200, oil at 100hrs, fuel filter, probably never, in water for the summer.
oil pressure under 80, norm for operation.

Moody Blu'
08-21-2002, 12:37 AM
i was gonna say the motor was probably tired and it sounds it...the compression is probably getting abit low and may need a re ring or possibly an entire rebuild to get back up to 5200 rpm's

another thing..
runnning the motor for 100 hours without a change in the oil is pretty scary....

maybe for 50 hours but a marine engine is run at prolonged rpms for long periods of time, its completely different then a car..

I change mine eevery 30 hours thats twice a season for me.(maybe 3 times this season)

HyperDonzi
08-21-2002, 01:53 AM
every marina says 100hrs, food for thought. i guess this winter, i will take the boat up "grandfather-in law" and see if he can help rebuild, his latest project is a 49merc....

Digger
08-21-2002, 05:53 AM
Broque no offense meant, that wasn't directed at you.

mattyboy
08-21-2002, 09:38 AM
so it's not pubity :p
It sounds like old age
1200 hrs is an long time!!!
rebuild rebuild rebuild

matt

HyperDonzi
08-21-2002, 11:54 AM
guess the boat gets a ride to michigan this summer to grandpa...
anyone know where yo find new rings and gaskets, plug wires for a 1990 carbeurated 4.3 gm?

Moody Blu'
08-21-2002, 01:42 PM
ok sorry digger im a little defensive..

hyper,

you could just re ring the motor but more then likely the cylinder walls are out of spec and need to be bored. yes there are oversized rings but im not fond of that considering you could run into piston slapping problems.

so you would probably need a bore and hone job, oversized pistons and rings ,new wrist pins, possibly new crank shaft bearings? I think thats about 500+ worth of parts?

My friend spun a bearing in his 4.3 and I keep
telling him to swap it out for a low hour 350.

I would suggest the same thing to you. It may cost the same amount of rebuilding the 4.3 or possibly be cheaper..