496 bbc afr heads new need help
 

I have a force offshore 2002 with a 496 bbc afr headed with a comp cam 575/575 cam with an 850 hp holly . Motor is brand new and runs and sounds great in neutral and in drive with the ears on. Oh this is on a brovo one drive 23 pitch 4 blade impeller, When ever i put the boat in the water and try to put it in gear the boat dies? Did some research and found out summit racing sent me the wrong piston was supposed to be 10:1 but turns out i have 8.8:1 compression. does anyone have any input on why it dies in gear? possibly because the compression is to low and has no torque when under load? ended up turning the air screws out totally and got the boat to get in gear and run but had no power at all. any help would be great thanks

This is not a too low compression problem. It most likely is a set-up,tune or ignition issue. What is the spec on this Comp cam? What rpms is it idling at in neutral? Does the engine have a shft interrupt system? This is most likely a simple problem and should be identifiable without worrying about the pistons and compression. The lower compression will cost you some power but a head mill and head gasket change can bring it back up without going through the block.

Best Regards,
Ray @ Raylar

We thought it was the mercrusier distributor so we change to a msd ready to run . But no difference . Weird Thing is the motor won't run with less than 45 degrees of timing .. It runs even better as u get close to 60 degrees of timing . We have checked tdc and the balancer to make sure it is correct. Idles great at 1100 rpm . Got the boat in gear and to run by turning the air screws all the way out on the carb and putting in gear at1500-1600 rpm . Boat drove like it had the anchor out slow and wouldnt plane . Dont believe the bravo ones came with a shift interrupt. I think that was the alpha drive that does. Let me add on ears the boat runs awesome . Great sound and response . Can even put in gear and accelerate. Totally stumped at this point .

Help !!! So frustrated !

If it runs with 60 degrees and doesnt detonate I'd say the cam timing is off, I'd pull the timing cover and check!

Got the distributor gear on the right tooth?? Those timing #'s tell me no. Could be cam timing too.

ill check
 

Distributor is dead on . checked it a few times even redropped the distributor to make sure. No detonation at all at 60 degrees thats crazy to me . I will check cam timing again.

cam
 

cam specs .575 .575
[email protected] 308/314
110. intake center line
[email protected] 254/260
lift .3390/.3390
lobe sepration 112.0

My bet is the cam is degreed wrong. Probably had the mark stamped in the wrong place. It will be very hard to figure that out with another identical cam to compare it.

Chris

With those cam spec's you better be running a good exhaust.

30 years ago (shows my age) I did not the the timing gears lined up correctly. I used the wrong dot. It would not plane out but idle fine on the hose. As I got older I always use a degree wheel to make sure the cam is setup correctly. I have seen them off 4-5 degrees and had to use bushings in the timing gear to get it correct. Its not that uncommon.

If you are truely using 60 degrees of timing you have a serious issue.