Mercruiser MX 6.2 MPI troubles?
 

Anybody having habitual problems with this stroker motor?

throwing rods #5 #6 cyl I think weve seen about 10 now

Thanks for responding, Phil.

Funny, this is happening with the V-drive engines in the 340 SeaRays down here too. Have not seen the problem with the 5.7's.

Are the rods breaking or what is happening ?

Pistons breaking! Bent pushrods, valves breaking. Rods bent.

A real mess. Normal MerCruiser exhaust elbow gasket failure on one, but the other engines' exhaust is fine.

Ed, do you think the fact that some of thses hull builders are specing too small of an engine and runnin it WFO all the time is an issue??

Could be.
This small-block is rated at 320 hp replacing the 310 hp big block. The weight savings looks good on paper, but this little stroker motor is having many problems the non-stoker motor, 5.7 MPI, 300 hp is not having.

are they using hyperuetectic pistons.... ???

seems they break the piston first then the rod. all have been under warranty between 10-200hrs. We also have no problems with the 350 mag or 5.7 Ed how many of these have you had because I thought merc said we were the only dealer in the country with this problem?????:angry-smiley-055:
Phil

4.5 quart oil capacity. So, using same pan as the 5.7L/350 MAG but Merc changed the dip stick to keep the crank out of the oil? How many people are overfilling this motor (thinking they are 5 quart capacity) and aerating the oil?

definently not the case by us

I have two engines in the same boat acting up!

Most marinas around here have at least one messed-up 6.2 sitting in their shop gathering dust and rusting away.

Trust me, you are NOT the only dealer having trouble with these engines.

What year 6.2's are you seeing problems with? I have 100 hours on my twin 6.2's in a 8000 pound 2006 Formula 292 Fastech. Run them really hard and not a lick of problems.

Looks like they have improved the exhaust design to prevent water getting into the engine...

Piston design most likely? Don't stroker motors in standard blocks have to go with shorter length pistons? That means the wrist pin and ring lands are all bunched up closer together. Where are the pistons breaking? Pulling the wrist pins out of them? Breaking around the rings?

I have 2 of these 6.2's in my 2002 baja outlaw..328 hours I run mercruiser part synthetic oil and change it every 20 hours..No problems at all except the IAC valve's went bad on each engine once....No unusual noises..They run smooth , powerful....I recently change the stock exhaust to stainless marine...The cast iron 5 year mark where they start to rust internally, then engine problems...so far i'm happy..better fuel mileage...I run them at 3500 to 4000 all day

Remember that even with the same pistons, the piston speeds are higher in the longer stroke 6.2, which increase forces on the piston. Interesting thread.

Michael

Man, this makes me a little nervous, since have twin 6.2's and couldn't afford replacing them if they failed. Is there anything to look for, what do I need to look at as far as rust in the exhausts? I have 500 hours on them in an 01 Chaparral 285 SSi.

Yikes, don't scare me, fellas...I've got 195 hours on my '03 FasTech 292 and an engine failure would keep my boat dry for a longggg time.

During which I would rip out both engines and rebuild with hardcore internals, make those mouse-motors roar.

That is exactly what I did, and they really scream as 383's. :ernaehrung004: The internals are pretty good to start, in the early 02 model year engines atleast. Re grind on the cams, 1.6 ratio rollers, and stainless marine exhaust, and they spit out 352.1 HP at the prop shaft in Bob Lloyds shop.

:DNice, and this is something I want more info on if you don't mind:
*You say 383 C.I., factory I thought they are 377 C.I. Did you bore for the extra displacement, and if so how much?

*Regrind on the cams meaning same cam re-used with new lobe profiles? Or new cam altogether? If new cam, why go with 1.6 rockers instead of just using a higher lift cam? how does that effect valve speed?

Is reversion a concern with the new grind and 1.6 rockers?

Was the 320 HP rating from Mercury at the propshaft or crankshaft? If it was at the crank, any idea what the difference is from your stock motor to 352 @ the propshaft?

Finally, the big question: How many MPH at top end did you gain?

Thanks in advance...

Have not seen or heard of too many problems with the stern drive boats, just the v-drive applications, so you guys can relax! The venerable small-block Chevy lives on despite Sean H.

Well I have gotten to become an expert on Merc 6.2's since I have had 4 fail this summer. The original 6.2's had 215 +/- hours with only a lift pump failure (fuel pump) and one IAC valve. Then the fun began, one ate a valve due to improper exhaust angle according to Mercury yet they approved the design when the boat was new in 04 but in 07 they claimed it was too slight of an angle (3 degrees too little for their new standards). Boat has Merc extended warranty so after a lot of complaining they changed both motors with reman motors.

With all new exhaust ($4500 cost to me) out to the tips the next two 6.2's went in the trash with less than 2 hours run time. I had one motor fail the mechanic had the other one fail on a sea trial. Merc explained the failure this time was in the reman process/ valves tolerances set too tight and after heat expansion they go boom. Now they put new blocks in and I am going to dinner tonight on the boat. 2007 boating time was about 4 hours in 10 months due to 4 1/2 months in/out of the shop.

The 6.2's have been good overall but I would be suspect of the reman. motors. The warranty cost on all this was about 48K. For that I could have gotten two new 496's!

To my knowledge the MX 6.2 is a factory built 377 cui while the 383 MPI is factory RE-manufactured with an over bore of .030" ...

To further complicate matters:
Mercruiser 377 CID__ 4.00" Bore X 3.75" Stroke
GM Crate 383 CID __ 4.00" Bore X 3.80" Stroke
Reman 383 CID __ 4.030" Bore X 3.75" Stroke

Cozzi all of our problems were in sterndrive boats!

Wow, have not been seeing that at all here. I thought maybe the 340 SeaRay Sundancers were too heavy for that package and they were over worked.

Now you got me scared also!!! I was going to order 2 of these in the next couple of days. I can get a really good deal on 2006 6.2's which were pulled for an upgrade. My application is in a 11,000lb express cruiser which has 250hp 5.7lx engines coupled to BravoII drives. Mostly running cruise rpm @ 3200-3400 rpm @ 30mph. Average season hours are about 85. WOT is maybe twice a season for a few minutes at most. Seems like older posts have nothing but good to say about the 6.2. The existing 5.7's are more than sufficient for this boat but wanted to upgrade mostly for EFI and all the newer technology that goes with it. Is there some kinda design change on the newer engines? What's going on? Help!! Maybe I should try to find 5.7's @ 300hp due to proven reliability?

OR maybe this is why Merc Remanufacturing seems to have an endless supply of 383 engines by rebuilding 6.2 failures?

I would love to know too. I'm looking to buy a Formula 280 ss with twin 6.2's .

Most of the problems I have seen have been are with big cruisers that should have 454's.

I have run the snot out of a 383mag in a little Donzi with no problems.

300 hrs no problems,but carry an I.A.C valve.

sorry for reviving an old thread but how are these 6.2 merc's working by now? I am waiting for a 232 6.2 to surface for a good price and would like to know about the reliability of these motors thanks!

Had two in my old Formula, like anything that is newer they had little problems but nothing major. Parts are cheap too.

No problems with the two 6.2's in my 2006 Formula. 400 hours and only IAC problems. Other than that, turn key and go.

I am wondering if the boats having 6.2 issues are running oil coolers. I'm surprised how many boats do not have oil temperature gauge(s) and I'm betting some of the bigger heavier boats are near 300º temps.
I have 15"x3" oil coolers and run full synthetic oil to keep temps down.

Which is the better motor? 6.2 or 350 mag 2005-2006 Vin..

I would buy the 350 HO mag or the 383 reman from Merc before the 6.2.

Any thoughts why?

I have - early 6.2 had piston and low compression issues. They have got better but 350 or the 383 did not see anywhere close to the issues of 6.2 . The 383 is 350 hp the ho 350 mag is 300 hp and the 5.2 was 320.

If you need any let me know and IMO the 383 is a better deal thru Merc. I have a couple sold as we speak, will get some more when needed

Well, I m looking @ a 2005 28ss Formula with twin 6.2s with 250 hours. 2 owner boat.