Originally Posted by thirdchildhood

The stout cam shouldn't cause the valves to wear. I did springs, etc. at about 400 hours as maintenance. There was no need to remove the heads. I also went with stock spec springs since they've worked fine for over 400 hours and I'm not going to second guess Mercury on their choice of springs. IMO this is a very good engine. Remember that when you're on top you will have haters.

Originally Posted by MILD THUNDER

Hate to say it, but unless you removed the heads, and actually checked the guide clearances, valve seat condition, valve condition, and so on, you're statement is purely a guess, in regards to what is, or isnt' needed.

At 400 hours, I'd be willing to bet the guide clearances, seat concentricity, and valve job, is no where close to what it was when new.

After time, when valve guides wear, things get loose. The valve no longer may seat itself concentrically on the valve seat. it might "leak down test" ok, but at 5000rpm, the results may be different. The relationship between the valve and valve seat, on an endurance engine, is critical. Not even so much as power is concerned, but for valve cooling, as that is where the majority of exhaust valve cooling takes place, when it contacts the seat. Valve seat cut widths, are only as good as the concentricity of the valve to seat. If the valve is only contacting 60% of the seats cut, when closed, due to a sloppy guide or workmanship, the valve can overheat.

Valves, and valve seats, have a cycle life, just like anything. Hence why different materials are used in different applications. One might get 300 hours out of a valve job with iron or powder metal seats and stainless valves, and might get 50 hours out of a titanium valve with copper beryllium seats.

I know you get a bit sensitive about the 525 mercury engine, because you have had good luck with yours. I personally think Mercury's package are about as good as it gets. But at the end of the day, its an Edelbrock cylinder headed, crane cammed, manley valved, pac' springed 502 GM based engine. It is not above the laws of physics. The sad truth is, there are many out there who have suffered the shortcomings of this engine, and frankly, I don't think its right to keep saying in so many words, that they are doing something wrong, or simply unlucky. Running a pair of 525's in a 42 Fountain or 39 Cigarette, is quite different than in a 22 Donzi. With that being said, I know of many who run the crap out of their 525's, and they have had good luck. It is a great engine, but not perfect by any means. I think alot of guys in the past saw "525EFI" merc engines in the boat they were buying, and assumed they simply are dead nuts reliable long life engines that just won't cost them an arm and a leg to maintain. Unfortunately, for some, that just wasnt the case.

Originally Posted by MILD THUNDER

Hate to say it, but unless you removed the heads, and actually checked the guide clearances, valve seat condition, valve condition, and so on, you're statement is purely a guess, in regards to what is, or isnt' needed.

At 400 hours, I'd be willing to bet the guide clearances, seat concentricity, and valve job, is no where close to what it was when new.

After time, when valve guides wear, things get loose. The valve no longer may seat itself concentrically on the valve seat. it might "leak down test" ok, but at 5000rpm, the results may be different. The relationship between the valve and valve seat, on an endurance engine, is critical. Not even so much as power is concerned, but for valve cooling, as that is where the majority of exhaust valve cooling takes place, when it contacts the seat. Valve seat cut widths, are only as good as the concentricity of the valve to seat. If the valve is only contacting 60% of the seats cut, when closed, due to a sloppy guide or workmanship, the valve can overheat.

Valves, and valve seats, have a cycle life, just like anything. Hence why different materials are used in different applications. One might get 300 hours out of a valve job with iron or powder metal seats and stainless valves, and might get 50 hours out of a titanium valve with copper beryllium seats.

I know you get a bit sensitive about the 525 mercury engine, because you have had good luck with yours. I personally think Mercury's package are about as good as it gets. But at the end of the day, its an Edelbrock cylinder headed, crane cammed, manley valved, pac' springed 502 GM based engine. It is not above the laws of physics. The sad truth is, there are many out there who have suffered the shortcomings of this engine, and frankly, I don't think its right to keep saying in so many words, that they are doing something wrong, or simply unlucky. Running a pair of 525's in a 42 Fountain or 39 Cigarette, is quite different than in a 22 Donzi. With that being said, I know of many who run the crap out of their 525's, and they have had good luck. It is a great engine, but not perfect by any means. I think alot of guys in the past saw "525EFI" merc engines in the boat they were buying, and assumed they simply are dead nuts reliable long life engines that just won't cost them an arm and a leg to maintain. Unfortunately, for some, that just wasnt the case.

Originally Posted by MILD THUNDER

Hate to say it, but unless you removed the heads, and actually checked the guide clearances, valve seat condition, valve condition, and so on, you're statement is purely a guess, in regards to what is, or isnt' needed.

At 400 hours, I'd be willing to bet the guide clearances, seat concentricity, and valve job, is no where close to what it was when new.

After time, when valve guides wear, things get loose. The valve no longer may seat itself concentrically on the valve seat. it might "leak down test" ok, but at 5000rpm, the results may be different. The relationship between the valve and valve seat, on an endurance engine, is critical. Not even so much as power is concerned, but for valve cooling, as that is where the majority of exhaust valve cooling takes place, when it contacts the seat. Valve seat cut widths, are only as good as the concentricity of the valve to seat. If the valve is only contacting 60% of the seats cut, when closed, due to a sloppy guide or workmanship, the valve can overheat.

Valves, and valve seats, have a cycle life, just like anything. Hence why different materials are used in different applications. One might get 300 hours out of a valve job with iron or powder metal seats and stainless valves, and might get 50 hours out of a titanium valve with copper beryllium seats.

I know you get a bit sensitive about the 525 mercury engine, because you have had good luck with yours. I personally think Mercury's package are about as good as it gets. But at the end of the day, its an Edelbrock cylinder headed, crane cammed, manley valved, pac' springed 502 GM based engine. It is not above the laws of physics. The sad truth is, there are many out there who have suffered the shortcomings of this engine, and frankly, I don't think its right to keep saying in so many words, that they are doing something wrong, or simply unlucky. Running a pair of 525's in a 42 Fountain or 39 Cigarette, is quite different than in a 22 Donzi. With that being said, I know of many who run the crap out of their 525's, and they have had good luck. It is a great engine, but not perfect by any means. I think alot of guys in the past saw "525EFI" merc engines in the boat they were buying, and assumed they simply are dead nuts reliable long life engines that just won't cost them an arm and a leg to maintain. Unfortunately, for some, that just wasnt the case.