Jeff Alaska

Can somebody help me? I have a stock Volvo Penta 7.4GL (GM 454) in a 26ft cabin cruiser. I am not looking to race. It jumps up on step easly in about 3 seconds. I would like to do simple things, on a tight budget, that would improve performance and fuel economy. Would the following changes be worth doing or a waste of money?
Thumper Exhaust System, MSD 6M-2 High Performance Marine ignition, MSD coil, Edelbrock Performer RPM Air-Gap Intake Manifolds the engine came with a Holley four barrel 700 cfm (I think 700 cfm) i am going to rebuild carb. The exhaust manifold and risers must be replaced, they are rusting off. Salt water got them. Thank you for your help. Jeff

MOBILEMERCMAN

Well Jeff its hard for a boat like yours to show improvement in performance. The only thing that will show up is increased torque. In my opinion those changes listed won't make a significant change. On a light speed boat maybe. Good luck
Jim

cuda

The only way to increase horsepower, it to burn more fuel efficiently. The two are mutally exclusive.

Jeff Alaska

Thank you for your input.

jafo

Ignition upgrades usually help the combustion process and can increase fuel efficiency. However, most of the later model factory ignition systems are quite good.
A much better investment towards your goal would be to ditch the carb/manifold setup for a factory or aftermarket fuel injection system. You'll get much better atomization of the fuel with multi-port type setups hence better throttle response and less fuel used during cruise. Starting the engine, especially after days or weeks of non-use will also be turn the key and go. Air-Gap manifolds are quite good, but the Holley carburetor has never been known for fuel efficiency.
Jim

robyw1

DITTO.. and no carburetor for that matter has been known for fuel efficiency

Jeff Alaska

Thanks, I will look into a fuel injection system. It is a older boat that was repowered in 1996. I will probaably be reselling in about 3 years so i am trying to not put too much money into it. LOL but it is a boat so it likes money and gas. What brand if any would be a better carberator?

Jeff Alaska

can sombody tell me if the thumper exhaulst would be a waste of money? I can get a stock one for 1/2 the cost.

AB From Windsor

Jeff if you are on a tight budget and want to improve your fuel economy. Leave the boat as it is and try not to drive it at full throttle. That is the right decision for your cabin cruiser. If you want to go fast then sell the cabin cruiser and buy an Offshore Powerboat but you can forget about fuel economy.