Hello everyone, this is my first post and first visit to this forum. That being said, I just picked up my first real boat. It's a 1987 liberator 211 with a fresh 300hp 350 and a merc drive. My question is, I can only seem to get a maximum of 4500 rpm at WOT. It has a 19p stainless stilletto prop on it. No matter what I do with the trim thats the best I can get. Any input would be greatly appreciated!

Need to know the max rpm's your engine can handle. Make sure carb is going full throttle, with engine off push throttle all the way forward and take a look down the carb and see if butterflies are open all the way

Max rpm's should be in the 5300-5500 range possibly even a little more as it does have a roller setup. I did check the carb, but it has a vacuum actuated secondary so im going to check that this weekend. Otherwise it does seem to open all the way.

Rpm's are controlled by the prop,assuming the carb is big enough and working correctly. google search prop calculator and you can put in your info and see what your slip is and experiment a little. Going down in pitch will increase rpm's going up in pitch will decrease rpm's. Or try www.go-fast.com for a prop calculator. What kind of shape is the bottom of the boat in? Clean or dirty, dirty makes a huge difference.

Where did you come up with the rpm range you feel it should be running in? Stock 350 motor in that boat would have been 260hp. 300hp isn't that much more. Where did the motor come from? Here are the specs for merc's 300hp
350 mag which only shows 46-5000rpm max. I'm sure it has a roller set up in it also. You may be at your max now. I don't think you would want to go any smaller than a 19P prop to increase your rpm's. Have you checked the timing at full advance?
http://www.perfprotech.com/store/art...fications.aspx

No, I really dont want to go any lower on the prop. As for the rpm range the guy I bought the boat from had the motor installed and Im going off what I was told I kinda figured it would be more near the 5000 mark. The timing was off and it is now 8 degrees advanced, and it is still only getting near 4500. I am going to check the carb this weekend to make sure the secondaries are opening when they should. the carb is a holley 600cfm. how much more timing if any can i get out of it without to much detonation? Or am I right where I should be?

I was talking about checking it at full advance to see if it is advancing as far as it should at high rpms. 8 degrees is what they tell you to set it at idle but that is assuming the distributor is advancing correctly. You should have 30 minimum to 34 maximum degrees total and it should stop advancing there by 26-2800rpm. In order to check the timing this way your balancer must be marked in degrees up that high. If not you can get timing tape to put on the balancer which is marked in degrees. Have someone bring the engine up slowly to 3000rpm while you watch with the timing light. Timing should keep advancing as the rpms come up and should stop advancing at 34 degrees before 3000rpm's. This is where you want to set your timing, not at idle as long as it is resonably still close at idle. If your distributor has centrifugal advance weights in it be sure they move freely and aren't locked up from rust and such as this would be a cause for it not to advance correctly.

I will check the timing this weekend. Thanks for the input!

I'd also check the tach. It could easily be off 500 rpm. Do you have gps speeds at WFO and 4500rpm?

the tach is off, it actually reads around 3600. and i dont have a gps yet but should have one in the near future. on the speedo it only reads 42 though.