no, the original motor was built for cruisers, it has now been rebuilt, decked, heads surfaced, higher compression pistons, different cam and who knows what else that all means it is no longer the motor that was built for cruisers. that is what everyone is trying to help you with. iron heads you are pushing the limit at a little over 9 to 1 compression and that is with premium fuel which you dont have. if it has the net zero rocker bolts then there is a chance the lifters are bottomed out. lots of factors going on here that can be fixed but you need to find someone that really knows boat motors and listen to the advice on here.

Bro, believe me, I'm as objectiv as **** but when you say dumb **** like "mismatched heads and intake" it tells me that you certainly don't know much about Gen V Big block Chevys. Go look at the gm truck lineup from that generation. It's a purpose built motor for high torque across a huge rpm range, if that's not exactly what a cruiser needs I don't know what is.

My mechanic is fine. He's honest and that's the most important thing . Already got burned once by dishonest guy that sold me the motor and first mechanic that put it in The boat. I am constantly throwing more and more at my mechanic and he is taking it on and knocking it out.

We are definitely going to revisit vaccum leak and triple check for them. It does seems.to be something of the sort. Good news is nothing seems to be physically broken. We will double check compression as a next step as well

The guy that rebuilt the motor really knows boat motors. He cosigned everything I discussed with him. It is still a motor built for a cruiser because of high torque and broad torque curve. Now it simply has ability to Rev up to 5500 rpm instead of 4400. If anything the biggest no no should be stock bravo3 and not a xr.

So for example when you say "lifters could be bottoming out" that's an actual useful idea of something for us to check into. Inserting your opinion that you think it shouldn't be built the way it was built is useless at this point. Motor is done.

I'm trying to leave this all to the professionals but .y mechanic is busy as is the Engine rebuilder and I'm just trying to assist in giving additional ideas on what to be looking for

sorry, was replying to arcticfriends round table like, not thinking about you in that. We , and some other long time oso’rs , have discussed many things over the years. So it was an in general comment. Newer engine designs and newer fuel injection enable lot higher compression ratio’s. They make 10:1 look weak. But it’s not on standard bbc and sbc

i can see why you took that tough.

My bad.

”Give your motor what it wants. Are tou listening ?” - D Morgan

If your intake gasket is leaking on the bottom side you can’t find it with carb cleaner. With engine idling, remove PCV valve from valve cover(if you have one) plug both breather hoses in valve covers with your thumbs or hand. With in 3-5seconds there should be pressure in crank case when moving your thumb. If it has vac instead of pressure intake is leaking on bottom side.
Summers coming-good luck.

I build tune and dyno reliable big blocks as part of my business so Im trying to HELP you, not dog on you. If the builder is a good marine engine builder, im kinda surprised at the compression vs cam with iron heads, but neither way, your right, its assembled. Tune it rich, preferably with a 02 sensor, yes, your mechanic can install one in your stock exhaust, Ive done it and be careful with total timing, Smitty

. Thanks, I'll try that.
luckily I live in Tampa so it's summer year round and I have a friend with this rig instead of my ****box ! Lol.

If the guy that rebuilt the engine, knew boat engines as well he represented to you, he would have NEVER used pistons that resulted in that much compression, especially for a cruiser type boat.
The engine you had built will make +/- 350hp at 5000rpms and spinning it past that is a waste since the torque will completely fall off. Its only making about 20-30lbs of torque more than your stock engine. It also should not be spun past 5000rpms with the cast crank and small rods. Bravo 3's can handle 400hp+ easily.

First thing that should have been done after the overheat was a compression check and leak down.

Why should you need to give your "mechanic" and "engine builder" ideas on how to do their job? They are the professionals who do this for a living and this really is not that difficult of a problem to fix if a person knows what they are doing. Your mechanic did not seem to know how to break in a flat tappet cam. If a serious problem is found, I hope you realize that your engine builder and mechanic are going to be blaming each for whatever the problem is.

Perhaps if I was in the great lakes region I'd have a plethora of options for mechanics. Here in Florida outboards reign supreme and fewer and fewer people will even work on i/o boats so literally finding a mechanic is a challenge.

Your way off on your horsepower and torque estimates as well. This configuration will make closer to 450 HP with torque numbers north of 500. In the case of my mechanic, he's a younger guy and carburetors arent his specialty. He's open to learning and because I have the time to research things as well I'm just trying to be another source for information for him. I guess I'll cease asking questions here because the more some of you guys answer the more apparent it becomes who actually knows stuff and who doesn't. We did numerous calculations for safe piston speed and a big block with stock crank and rods is easily capable of spinning past 5000rpm but I do agree that the power and torque drips off around that point so no reason to go much higher

Then build a replica of a GM truck engine. And I believe most are injected and are computer controlled!