Rpm's

[khaynes]

I had my boat out for the first time this past weekend. Everything ran and worked fine. Max speed with the speedometer was 40 mph @ 4800 Rpm's. I forgot my GPS. The boat seemed to cruise real good at about 4000 rpm's. I noticed on another thread someone said 4000 rpm's may be to much to cruise at. What would be a safe max cruise rpm for a 7.4 carb engine. Thanks for any info.

 

[Hampton]

I believe that at or below 4000 would be safe, but the mid 3's will be more economical if it holds a steady plane, and will probably reduce wear as well.

 

[fc3]

I had my boat out for the first time this past weekend. Everything ran and worked fine. Max speed with the speedometer was 40 mph @ 4800 Rpm's. I forgot my GPS. The boat seemed to cruise real good at about 4000 rpm's. I noticed on another thread someone said 4000 rpm's may be to much to cruise at. What would be a safe max cruise rpm for a 7.4 carb engine. Thanks for any info.

That someone would be me. The other poster had an inboard powered boat. Typical WOT RPM range for the standard (not high performance) 7.4 inboard is 4000-4400 RPM. Thus he's running the boat too hard even if her max RPM is at 4400 since that's about 90% of max.

Sterndrives are a bit different. For example, the 310 HP MPI engine's WOT is 4200 to 4600. 4000 is still a bit too close to max for my comfort. That' something like 87% if the boat tops at 4600. The 7.4 Mag MPI sterndrive versions have a WOT range of 4600-5000. There 4000 would be around the top end for cruising assuming the boat's WOT was 5000 as that's 80%.

WOT range should be stated on a decal attached to one of the rocker covers.

Best regards,
Frank

 

[sbw1]

3500 to 3550 is about the max cruising rpm for that engine. You will get lots of life out of it by staying at or slightly below that range assuming that is the way it has been run during its history and the PMs have been performed on schedule.

 

[khaynes]

Thanks. Thats where I'll keep her. Unless someone trys to pass me.

 

[fc3]

Thanks. Thats where I'll keep her. Unless someone trys to pass me.

Have you considered something quicker that might be better suited?

 

[khaynes]

No this is just fine. The last serveral years we had a pontoon. This machine feels like a rocket at 40 MPH. I know thats not real fast. But when your max speed was 24 MPH. Last weekend I felt like I had a Baja.

 

[Priority]

I recently picked up a 94 sundancer 30 with twin 260 inboards anyone know the optimal cruise speed and rpm for this boat?

 

[Tail Chaser 661]

Thanks. Thats where I'll keep her. Unless someone trys to pass me.

I saw you were from Henderson. I was thinking near lake Meade in NV
I was gonna come looking for you after my 8.1 Mag repower:lol::lol: Just kidding,
The most efficient rpm to cruise is usually near your engines Max Torque.