tssteph

I clamped off my return line yesterday and ran it WOT for a short burst. The pump could not keep up with the pressure at WOT. Fuel pressure at an idle is real eratic also.

Looks like I need a new pump for the port motor. It also seems that Mercruiser has a newer version of the high pressure pump and cooler for the cool fuel system and you can't just replace the pump any more. I am having a hard time finding one in stock anywere.....

mo3d

Well the results are in and while bad, it's not too bad.
Hole burned thru #5 exhast valve (about a 1/2" long), crack in valve seat, cylinder bore scuffed, and the beginnings of a hole burning thru piston.
The good news is I can get away with 1 piston and hone the cylinder.
Head has been sent out for a new seat, carb has been sent to
Nickerson, and my wallet is much lighter now and wont pull my back pocket as much.
The engine only has 108 hrs and I'm not going to replace all the pistons.

Anyone know where I can get 1 new OE piston ???

HPJunkie

Mo3d, sorry to hear about your experience. That same thing happened to me exactly. #2 & 7 pistons got hot and lifted the ring lands, broke the rings but i was lucky as well.
I pulled the motor honed it out and put a new set of takeout pistons and rings from a std bore 502 and am back on the water. Some of the bigger hot rod type marinas will have some of them around I only paid $100 for mine from some nitrous guys that build 540's right out of the crate motors.
What I had not realized is that the intercooler had started to or had been plugged up with leaves pebbles and snail shells from stopping at beaches and navigating shallow water (like the chain of lakes Fox river area). Make sure you backflush that intercooler unless your sure its ok.
I had a nickerson 850 on the motor at the time 30* timimg and it ran great. Dean nickerson has since switched me to a 750 body and changed jetting but the timimg is still 30 deg. block temp is about 110 deg and after a top speed run it goes to 125-130. I now have aluminum heads also. This is the 3rd year on this motor with the new takeouts in it and still runs fine.
Dean told me to run more rpm (less pitch) in the prop. For 2 reasons: 1. less load,strain, whatever on the motor 2. the lower pitch on a single engine boat like yours and mine would be easier on the drive. How long do you actually run it at full throttle (81mph)?
If not too long because of water conditions and or boat handling at those speeds You could consider less pitch.( itll go like a rocket)
I turn mine about 6000 for only a 10-20 second burst just enough to race someone. I hope you can get it going before the season is over. Greg

HPJunkie

Posted twice sorry.

mo3d

Well like most people, I don't WOT for more than 15-30 sec.
With my new found power, I'm happy with cruising at 50-65 mph 3500-4300 rpm.
I talked to Dean yesterday and he has serious issues with my fuel system setup. I going to have to bite the bullet and step up to his recs w/ the Aeromotive setup.
I plan on replacing all the exhaust valves as per Deans rec.
Hopefully will get the engine pulled out early this week.
I'll keep you guys posted.

Mo