that's an understatement

How come only engine 1 and 2 were covered? If merc replaced the first 2 they should replace this one too if its all the same issue? You should not be getting reversion on a completely stock set up

The 6.2 can have two different height risers. I guess you don't have the Merc 'Y' pipes that has butterfly flappers in the upper part to stop water surge while throttling down.If you have through transom exhaust pipes ,internal flappers or external flaps would stop surge. The 6.2 doesn't have a huge overlap cam so reversion isn't an issue. There are a lot of 6.2's in sport boats, cruisers etc.... without issues, mines included. I'd be looking for mechanic #3 as well.
If mechanic#1 knew there's a problem with reversion or back surge, he could have suggested to switch to Kodiak aluminum manifolds that has anti reversion
dam inside the riser plus saving weight that would have been a bonus too.
240hrs and counting with through transom exhausts.
http://www3.telus.net/spectrasonly/Twin%20377's

These tips have internal flappers.

http://www3.telus.net/spectrasonly/E...ect%20complete

I smoked (6) 6.2 motors in less than 2 years.....Mercury replaced them under warranty but it got to be a joke. 2 motors blew up before I even got the boat returned to me and all the work was done by a Mercury Platinum dealer!


1. They argued the exhaust angle allowed inversion (Manufacturer disputed that Mercury approved the angle so Mercury covered it). Motors were salt water only, 240 hours and I bought brand new exhaust at this point.
2. Mercury used reman'd blocks, paid the dealer to swap the accessories
3. Two of the motors blew up on the test drive (by the dealer) I never even turned the key on those motors.

Yes it has pretty much always been the same problem loss compression with rusty spark plugs in a few cylinders, I had Mercury racing tips installed when I first purchased the boat with internal rubber flappers and external flappers, both flappers present still. When installing the 3rd engine after extended warranty dealer sold me ran out which caused me to seek out a mechanic in lieu of the dealership prices. The mechanic showed me the risers and manifolds full of rust and holes. His diagnosis / guess was rust in exhaust, engine 2 was replaced,old exhaust put on that failed. The boat did have cpt choice however when replaced with marine SS that was eliminated. The angle I am not sure of looks not very high. I purchased a

That was less then 2 years ago and less then 100 hours.

Ah, now we are getting somewhere. Who did the install on the external exhaust? Do you have an engine compartment pic you can post that would show the angle of the exhaust hose between the risers and tips?

I dont have any photos to offer, But same dealer I purchased the boat from installed the tips. They said it would not void my ext warranty and it didnt, As I began replacing engines almost immediately. The boat came factory from Baja with through hull exhaust / CPT Choice, the tips that came through the hull were what the salesman called muffler tips that could be replaced for louder sound. The factory tips look (o) Circle with a little hole in center no flapper

I presume they installed hoses straight out since the mercruiser riser's output flange is almost level. Other manufacturers' risers are usually sloping downwards. After I swapped out my 'Y' pipes I installed elbows behind the risers and routed out with using another elbow [ like an 'S" pipe ]dropping the exhaust tips out lower level.

yes pipes were straight with slight down angle