Thanks SB, I think you hit it n the head, I need to find the problem, more money thrown at the wrong solution will not solve the problem.

The fuel this time was just recently purchased from marina, 89 octane stuff, 8.75:1 motors (stock flat top pistons).

The engine builder has some 30 years experience, the mechanics owns a boat sales and r/r shop, both shop owners did the work themselves (did not farm it out to employee).

Ignition is the same as came in the boat, fuel lines are all stock merc stuff. Your comments about fuel is make me look close at spark plugs for indications of fuel problems.

No fuel gages, will call Fred and have him send some.......

new mechanic is a different shop owner, I hate to switch people in the middle, but it only seems reasonable, motors are new crate motors, so I swapped shops there too.

Background, everyone who touches this boat I have close, PERSONAL relationships with, my only request, which I make very clear, is to baby sit my stuff, and charge for extra time if needed, but do not farm it out to a employee. I do not think incompetence or negligence has played a part, but I also know no one walks on water.

again, the comments are apprecieated...

Finding a good, reputable engine shop that is familiar with and knows what it takes to build a hi-perf marine engine that stays together isn't always an easy thing. Hopefully you'll find your way before it costs you even more of your hard earned $$$. Just remember, when dealing with these so called performance engine shops you don't want to become one of their test bed guinea pigs! Anyway, I hope all goes well for you from here.

forgive my ignorance but is there some reason you just don't call mercruiser and buy what you want from people that actually really do this with fabulous success ?

Yes, and no...

Yes, that was the purchase yesterday....

No, we started with good motors and a solid foundation, in a boat that was running well (not fast, just well). We started with a fee changes to good motors. When they blew the top end (the new stuff) was still new, and it was cheaper to rework short blocks than buy new, so we did that, then next time around the machine shop picked up the rebuild tab, now is the fourth time, and all we have done is sit motors on the floor.

So it is like mission creep, a "we went this far, the next step is less expensive than new motors"... those were rational decisions based upon the ingredients to that point.

Now I am irrational, so I bought 2 new, GM sealed, with warranty, 425 ho motors.....

My concern is making sure I do not destroy these motors with the same problem that has yet to be discovered. I can not afford to test each and every component to see if it blows the motors until we find the root problem.

yes... i see that now... the foundation WAS good so that was the right choice. my boat had junk in it when i got it and i chose to buy 2 factory 502 mag mpi rather than rebuild the two that i had... completely dif situation...

am curious ( off topic) about one thing tho... early on i wrote a post about dyno numbers and correction factors and when the motor builder in question mentioned here posted on this site a dyno sheet with some unbelieveable results and i asked for the sheet with the uncorrected numbers , i was savaged as being negative and generally too cynical to be allowed to breath the same air as real people... now , suddenly dyno cynicism in general and this motor builder specifically is fair game... i am curious what suddenly changed everyone's mind.

Not sure I saw that post, but I would not trust a dyno that was operated by the builder 90%+ of the time. I am big on that "independence" thing, I sent these to a guy with a dyno who was not an engine builder. That does not mean I got perfect results with the dyno (but I have faith in them), but I know the guy who did the dyno work understood his roll as "verifier".

We all know way to many people use inflated Dyno results to sell at inflated prices. The old time, been around forever, know their stuff guys know that crap never works, but the "live hand to mouth, want to make a giant splash, gotta prove I a mbetter than other" guys, well, that is a game some want to believe in....

His 540cid/750hp build with sheets on this and another forum. Some respected members 'in the know' busted it thru some major 'CSI work' and the thread got shut down and those members got got warnings.

Generally - the builders here that help on the threads vs brag about 'family recipe' and '10yrs ahead of everyone else in engine technology' etc,etc are the ones to put on your list of possible builders to do a build.

stevesxm - you've been a part of those threads. LOL. SO, don't think all dyno sheets are lies, you just have to be able to decipher them. Only one person posting questionable data that I've seen, which is causing quite a ruccus. (sp?)

Anyway - being relatively new here there may be others, but throough all my 'searches' only one name has stood out.

there are laws of mathematics, two engines with like components built correctly will produce the same HP, there are things that can be done with flowing heads and intakes and all, but they are mathematical in nature, not voodoo, so they are repeatable... and the market is full of smart, and dumb, people. No one person has "the secret voodoo formula", and if they did, the second motor they sold would be to a compeditor who would tear down the motor and figure out the secret....

I strongly believe if you take 10 people, put them in different rooms, give them all the same ingredients, and a problem to solve, 75% of them will come up with the same or very similar solutions. Shops are no different than those rooms, and the inputs are the vendors in the market. There will be slight differences, but among the top 10% (some of whom post here) there will be little if any difference. If this were not the case Merc could not sell 500EFI's, they sell 500EFI's because they know consistent application of certain rules and ingredients produce consistent results. The difference in builders is attention to detail, follow through, and customer service.

Now back to mine, it is not consistent, so maybe there is multiple problems??????????

i have your solution right here.... i just rebuilt the two 454 / carb 9 to 1s that were blown up in my boat when i got it... fresh off the dyno at 975 hp each on unleaded regular.... 10 k each and ill pay the shippig...

honest...

lifetime warrantee too

send them over and we will run them..........