I'm interested what kind of problems you had with your headers. Mine cracked at the "diamond" welds where the four pipes combine to one. I got some water in my oil which clogged the filter then sent my oil temps high. Only happened on one motor for me so far. Checked the cyliners for scoring and compression everyrhing OK.

I have seen these motors fail at 80 hours and make it 200 hours. However, the motors I have seen for more preventative maintenance have the higher hours to show for also.
Your mechanic is probably pulling the drive off to grease the input shaft every 25 hours if the alignment is good and the motors are raced mounted. This is also a good habit to get into. I would start with cylinder leak down on your motors and they should be around 10%-12% with your motor and hours on them. Compression check is more of a waist of time for good info.
Have you used good quality fuel even though they only require 87 octane?
170 hours is getting up there for hours on the cylinder heads with the spring psi and fuels these days. If you are going to continue to run with out doing valve jobs just continue with cylinder leaks downs more often..
Thanks, Cam-shaft/

I have seen cracked headers at the collector in which you are reffering to. This later caused a spun rod bearing, in which there was an oil temp issue. The bearing failure was probably due to debtination from water in the combustion chamber. Thanks Cam-shaft.

CMI Sport Tubes leak unless they have the "cool collar." If your headers leak, buy new ones. They are $12k.

Been there, done that

Hey Mark ... I understand ... I'm no expert and just try to soak up some info .... Some people try to lube the Coupler and U joints in the boat ..but I'm sure removal is the way to go ...Seems the solid mounts are better too ...I lloked and almost if not ALL HP merc motors have had the solid mounts for a while. ......m

I have 310 hours on my 2003 525's. No signs of any problems but I believe that preventitive maintenance is the key to a happy boating season.

New springs, retainers, and valve job.
New CMI headers with the cool collar upgrade.
Complete drive overhaul with new gears and bearings.



Jay

stop buying tubular headers and get a set of stainless marine...............they are pretty(cmi) but they always seem to give people a problem...................just a opinion .............

My S/M dry pipes are 12yrs old, only salt water, I flush them after use 1994 to 2006 and they sound great loud