Would like to take everyones money but changing to DANA exhaust really a retune is not needed. The dana exhaust are not full runner lengths compared to real headers.

Also number 2 is the stock intakes - stock throttle bodies - stock heads are still the cork in the bottle aka air flow -- keep in mind basically more air flow in requires better scavenging air flow out. You only changed exhaust and the stock 496 is not a high HP peak rpm engine anyways. At 5 K rpms there is nothing left for a jist. The heads are weak for any proven decent gains along with the cam and so on..

On the water you really are not going to see / feel anything in much of gains with a 98 percent stock engine. I like making money to live decently but I would be taking your money. A good size credit card limit and time along with testing for real tuning on the water is needed for the 496 to see great gains. The old saying is 1000 dollars for one mile per hour gain if not more $$$$ on the water.

BUP……recently i was running my boat on the trailer getting ready to take it out…..out of no where it died…i went to start it and nothing…not even the fuel pump priming….i replaced the batteries seeing how one was bad and not holding a charge…..now when i turn the key it doesnt run the fuel pump prime till about 15/20 seconds later…and i verified its not getting spark either…..ive checked all the obvious things and came up empty handed…im thinking the ecm finally gave up…it was running one second and then it was dead with no spark and a delayed fuel pump prime….have you are anyone else ran into a problem like this?? Is it most likely ecm related and is it something you can fix??

not everything relates to ECM failures, ,

you need to scan it and see if you got cranking RPMs, if you don't, I would start with checking crankshaft sensor output

I already replaced the crank sensor wasnt that…and would that effect the fuel pump prime delay….i do plan on taking it to a shop if all else fails…and have them verify its the ecm….although im not getting any trouble codes

Trentdawg since you're new.
Unfortunately BUP was banned from this site. You'd have to call to get any advice from him.
His link below.

Boats Unlimited | Marine Technician Service | Inspections (boatunlimited.com)

Hi do you have a ecu to my 496 ho 2008 model?

Are you still repairing ECU's?

hello, I need ECU 866 090 T04, 2010. Mercruiser 496 HO. My ECU have no communication..
Need to buy used one. since l am offshore, repair is difficult. Please advise.

Martin,

Let me check the numbers on mine. Might take me a minute. It's a 2001 MY unit, so it might be a long shot. I won't have it available until we get my rebuild up and running, just in case we need to go back to the 555 .

Thanks. Brad.

Brad, are you anticipating problems with the Holley HP?

Padraig