Engine replacement

[Lake Erie Lib]

I am replacing the engine in my 1986 Four Winns Liberator, it came with 260 mercruise 350, should I replace with a 454 big block? If so what modifications will I need to make?

 

[Bondo]

If so what modifications will I need to make?

Ayuh,..... Welcome Aboard,..... If that's an Alpha drive on it,......

Everything from the pulleys to the prop,.......

A big block really needs a Bravo drive,.....

 

[Lake Erie Lib]

I was thinking that, maybe not worth the expense, but the 260 hp, is weak in this heavy hull...

 

[achris]

... should I replace this boat with a 454 big block?...

Only if you have something to put the 454 in...

Ok, serious again.. How big is the boat? What are you planning to do with the boat? What sort of top speed do you need?

Chris........

 

[Lake Erie Lib]

I know, typed way too fast... I would like 50mph, top speed with the 260 hp/350 was only 35-38 best. Takes too long to plane, especially with more than 2 people in boat... Just not experienced enough to know all the modifications I will need to make, if I decide to go big block...

 

[andrewterri]

What was your rpm when running 35-38? What is the dry weight of your boat or what do you guess?

 

[Lake Erie Lib]

4100-4200 rpms, 4800-4900 lbs guessing, It was 5200 with trailer...

 

[andrewterri]

Something does not sound right. I bet that tandem trailer weighs around 800 lbs making your boat weight about 4,400. That is about the same weight as ours and we have 220hp and gps the boat at 48-50 depending on water conditions and loading. I am wondering about your prop. I am not as smart as the other people on here that know everything about boats so what is you wot rpm? If you don't know there should be a tag on your engine that tells you. 4100 seems low to me. Sounds like you might be over propped. If you holding good compression you should be running more than 35-38 unless your hull is covered in algae.

 

[andrewterri]

What I found showed your wot rpm at 4400-4800. I would differently get the correct prop on the boat and see how it runs before you start doing anything with the engine. What size prop is on your boat now?

 

[achris]

Your boat weighs about the same as mine. I have a 220hp V6 and hit 42 knots with ease. And if you're not seated or hanging on when I give it the word, you're on your ass.

You're only pulling 4100-4200rpm, way too low. Slow to get up on plane, all says prop too big. Find the details of the prop and post them here.

Chris..........