2 questions on RPM and on lean

[peacekeeper6]

Basically i have a 260 HP mercruiser with an alpha one gen one drive. with 4 full grown men and one little 6 yr old girl the boat was WOT at 3900 RPM and fel sluggish getting on plane. This is the larson that i have in my sig. the prop is a GP33656A. What is a healthy RPM? I think the prop is original it is kinda dinged up. also it leans alot to the left and feels very dangerous on plane, what is this cuased by? i had a 21 ft bayliner ski boat and i never had this problem with that boat. thanx for the advice!

 

[bruceb58]

Re: 2 questions on RPM and on lean

What is your history with this boat? New for you? A 26' boat with a 350 motor is not going to be a speed demon...that is for sure.

Since we can't see your prop, I believe we could only guess if that is your problem. One man's ding is another man's dent. If it's a dent, it can throw the pitch off.

You have a spare prop that is in good condition tha tyou can test with?

 

[Don S]

Re: 2 questions on RPM and on lean

You should be looking for 4200 to 4600 rpm at WOT with a normal load. If you carry "4 full grown men and one little 6 yr old girl" as the normal load, then prop it accordingly. But make sure the engine is tuned and running properly, the bottom is clean, and it's trimmed properly. If you are running with the trim all the way down, it will never get full rpm.
Not sure what that prop number is, but if you post this in the prop forum, I'm sure someone will recognize the number.

 

[peacekeeper6]

Re: 2 questions on RPM and on lean

sounds good, i dont have a spare the props are hella expensive, but i am gonna get another soon ad use this one as a spare. The normal load is 4-5 people and max is 6. I didnt want a speed demon just wanted to know about my RPMs i did have trim all the way down. The boat isnt new to me and i beleive with my old upper unit i was turning around 4300-4600 RPM with two people aboard. But i had my whale fin on it at the time and from what i hear that doesnt do anything. Could that be the culprit?

 

[bruceb58]

Re: 2 questions on RPM and on lean

Going out on the water without a spare prop is like driving a car without a spare tire...only worse!

You didn't say before that you changed the upper unit. What else have you changed and are you sure your gear ratios are the same as before?

You also didn't say that you just added a whale fin. That could easily drop your RPM by 200. I would remove it and see how it runs without it.