Doesn't that add more stress on the valve train though? I thought big blocks didn't like a lot of RPM? What's generally a safe RPM to spin a BBC? Merc recommendation is usually around 5200.

That is some good info right there. Thank you

If I had the tools and space, I'm sure you're right. I however, need to arrange someone else to remove, another to rebuild, and the first guy to re-install. I truly envy some of you guys.

merc 1075's go to 6200,I spun my old 454's to 6800,and held it there for 25miles.,would have gone further but started to run out of gas,,in the tank.
need to get the valve springs right and they'll spin up.

Exactly.

Old sixties NASCAR big blocks turned well over 6k plus for 500 miles with parts that were much older technology and heavy. Spinning a more modern-built Gen VI 502 to 6k for short sprints (with good oiling and cooling) isn’t going to hurt it all.

Don’t be afraid to spin it up!

Just disconnect everything except the engine mounts and have your mechanic pull it and set it in your truck.
Do you have a garage?? Does it have a steel beam or wood ceiling joists that you double up to strengthen??
If so all you need is chain hoist and an engine stand which will cost about $300 total.

That would be an awesome video.

First option will most likely be the way to go.

My boat won't fit in the garage.

If you have a decent amount of room to sit and pull apart the motor in the boat is do it in the boat. Just have to keep the internals clean when you start pulling it apart and keep all the parts coming off organized. I understand not working on a side by side in the boat, no f’n way, just a terrible setup for any kind of maintenance period, but a single or staggered it’s not that big of a deal. Even with a hatch that only opens to maybe 30 degrees I didn’t have much of an issue pulling a head on my blown 525s. Having someone to hand the heavy parts as they’re coming off really helps. If you can remove your hatch that makes a world of difference too.

I would absolutely agree, the HP increase to get from 54 to 70 would be probably around 250

Talked to the engine guy today.

He wants the whole engine. (Actually just the long block. says I can save a few bucks by removing all the accessories)

Hope it's just the top end. Otherwise this thing just became a REALLY expensive Hp 500. Coulda bought a rebuilt 525 for what I'm looking at now. (including purchase price of the used engine)

That sucks to hear, but based on what you described, it’s probably just up in the heads. Doesn’t hurt to get a sampling on the rest of its condition while out though.

Looks like you have through hull exhaust, so I wouldn't worry about the cam. To get water ingestion you need back pressure and you'll get very little with through hull exhaust.


I'm surprised the shop said an hour to remove the engine. It comes out quick, but not really that quick two guys can have it out in an hour, but that's two hours shop time.


I agree with most everyone, I want to see the bottom end and make sure it's solid. However, sounds a like top end problem. Did you hear noise from the engine when you launched? The poor leak down could be from bad valve adjustments, bent push rod, leaky valve, or any number of other things. But it does sound like a top end problem. Poorly aligned piston rings during assembly can also result in a bad leak down test, but this is such a rookie move I doubt that's the issue. If the motor was new and wasn't fully broke in, i.e. rings seated, that could also do it.


Based on the thread, pull the motor, have it torn down, inspected, then reassembled. One problem though; I fully balance all my motors - it makes a HUGE difference. So, if it were MY engine, I would have the whole thing re-balanced to be sure.