Boat Engine

Reply Subscribe

Thread Tools

Search this Thread

Jan 23, 2004 | 03:07 AM

willd

Thread Starter

Elder User

Joined: Oct 2002

Posts: 743

Likes: 1

Boat Engine

We are going to be rebuilding a boat engine pretty soon. The boat is an 80's model with 460 in it. Right now it has a performer intake and carb on it ( not sure of CFM yet ). It cruises real nice at 3000 rpm, 4100 is about all it will pull. It's worn out and needs rings etc. My questions is this.

What rpm assuming it has the good truck rods in it, can we get away with for flat out running? I'm thinking 4500 or so is about all I'd want for long distances. For short distance ( like 1/8-1/4 mile) I wouldn't be afraid of 5500 or so. I know that piston choice and rod-bolt choice has a lot to do with this, so we will put in forged and arp bolts.

I want to stay with the performer intake to keep the low end torque. How about a cam. Does the newer competition extreme cam work pretty good? I will be matching the cam etc to the powerband. Right now I'm thinking 1800-5500 for the powerband with cruising rpm's of 3000-3800.

I've built plenty of car engines before, but the longevity at constant high rpm is kind of new to me. Most of my engines have always been r.v. kind or short track with very few spinning more than 6K rpm for short periods.

Thanks for any ideas and input.

Jan 23, 2004 | 06:24 AM

DeenHylton

Elder User

Joined: Jan 2000

Posts: 966

Likes: 2

From: Crooked River Ranch, OR

You need to call the cam MFG. and go with their recomendations. Boat cams are not the same as automotive cams. To large a cam or too much exhaust duration on a boat motor will suck the lake water right back up in the exhaust manifolds (and then into the motor...not good!). That's assuming your exhaust outlets are below the waterline. If your running headers...then that's another story.

Going with forged pistons and ARP bolts is a definite yes.

Deen

Jan 26, 2004 | 02:42 AM

Ray Hamel

Freshman User

Joined: Oct 2003

Posts: 31

Likes: 0

From: Michigan

Hi, there Willd.
You should check out this site for boat engine information. It is a good site and the people there are very helpful. I run a 460 Ford in my 1978 19' Nordic jet boat. On this site you can go to spot that suits your needs best (jet. v-drive, etc.) Also you can access Rex Marine on this site to find performance parts through their catalog. Hope this helps.
http://www.hotboat.net/