Are the new holley 800 marine carbs the same as the hp 500 carb from mercruiser, or do they modify them. What is the max hp this carb can handle without being undersized.

From what I understand, they just richen them up some, other than that they are stock, you can be up in the 550-575 range with one at the RPM we turn...Rob

That's right. Change the jets to 77s in the front and 90-92s in the back and you should be good unless you have a wild cam. Then you may need to get some vacuum readings to adjust the power valves. Generally you will be fine though. I replaced my hp500 carbs with jegs marine 800cfms. Exact replacement.

I have notied a few of them actualy drop HP on the dyno. They are not worth the cash it takes to buy them.

Call a good custom carb guy and he will build you better than that for usually the same money.

There are some guys on here, or I can give you a recomendation also.

On the other hand, the race series Holley is a good carb. All you need to do is add the J- Tubes to make it legal.

I am not sure what the difference is, but there is a difference.

It is noticable on the dyno.