Proper RPM for 1974 135 V4

[KenPSr]

New here and not sure if discussed before in the over 2500 posts so thought would ask the question here.

What is the proper RPM for WOT on my 1974 V4 135? I have been told that 6000 is too high and should not reach that level but yet I have seen where the RPM range has been stated at 5000 to 6000. I have been trying to find the correct prop for my fishing boat (18' Starcraft WT).

I have a Raker 13 1/2 x 21 and it labors out of the hole but then changes vibration and pitch sound and jumps on plane and runs @ 5600 WOT. It is the first laboring and vibration I don't like and find troubling.

 

[ezeke]

Re: Proper RPM for 1974 135 V4

The "full throttle operating range" for the 1974 135 is listed in THE specifications sheets of both your owner's manual and factory service manual as 4,500 to 5,500 RPM.

The consensus is that motors of your type should be propped to reach 5,800 RPM maximum at WOT under normal operating conditions for your motor. This will help to prevent the engine from coking by not being overpropped.

I ran a 1976 18' Starcraft runabout until last year with 14 X 17 aluminum 3 blade OMC propeller. If I pulled two skiers I used a 14 X 15.
You can expect a good hole shot and around 40 MPH with a light load with the 14 X 17.

The superseding OMC/BRP propeller number is 763463. I also used a Michigan Wheel propeller of the same size with good results.

 

[KenPSr]

Re: Proper RPM for 1974 135 V4

Thanks ezeke. I have a Michigan 14 x 17 and will give it a try. In the next few days I will have my boat out again and try the 14x17 and post the results. Thanks again.