First off hope everyone is doing good catching nice slabs through the spawn. I purchased a used 21'8" seapro center console boat with a 150 suzuki 4 stroke. Im running 35mph at 5000rpm. The boat is capable of running faster but It makes me nervous to push it any faster. I have owned bass boats in the past and never run rpm and speed so high and with as big a gap between them. I have never owned a boat this heavy either. If I push this boat to 40mph the rpm jump to 6000 and I still dont have it wide open. Is this normal for this type of boat and is it safe to go ahead and open her up? Thanks for all the help in advance

JMHO but if you have throttle left at 6k you need a bigger prop,especially with a four stroke.

It should be propped to hit 6000 rpm's at full throttle.

Does sound like you need a new prop. The previous owner may have had it a little under propped because they had it loaded heavy or liked a better holeshot. There’s a lot more to consider than just speed and RPM. Contact a prop shop and they will walk you through the process. WOT speed and RPM is the first thing they will ask you.

maybe look up the specs on the motor, 6000 rpm at WOT might be normal. is the motor cavitating when you give it the beans? are you tilting and trimming as u get up on plane to make the prop bite?
Thats a big, heavy boat u have.. On my bayliner, there I have to tweak the tilt and trim once I get on plane, to get the right bite from my prop.
first, what prop are you running, its stamped on the prop. diameter, pitch, and number of blades..
when it comes to props, theres always a compromise.. I like a power prop, to get my boat on plane, and just cruise . if I want to really push it to the max, once I get up on plane, I tweak the trim. I can get my 20 ft bayliner, a very heavy fiberglass boat, with a 115 yamaha 2 stroke to around 38 mph, loaded with tackle, anchor, full tank of gas, ect.
I dont want my motor straining to get the boat up on plane, it hops right on top
as was mentioned, a good marine mechanic can do some quick calculations and nail it down for u pretty quick.
Also I like running aluminum props, the seem to let the motor spool up quicker, they are lighter.. and if I hit something , chances are the prop will bend or break, rather than destroy my lower unit,., the hubs are supposed to slip, but sometimes they dont.
My stainless prop is my back up prop.

Well I just stepped out and It has a 4 blade stainless steel prop. I would have to pop the prop off to get the pitch but I would guess it is a low number, possibly 21 or lower. This boat has no problem getting out of the hole and of course once out I go ahead and start trimming it up till its good and comfortably out of the water. So are you all thinking I need a higher pitch and possibly switch to a 3 blade prop? I forgot to mention this boat has a hydraulic jack plate. I generally have it set on 3 if that means anything.

WAY too many variables to give any prop suggestions at this point. If you are running 35mph at 5k RPM and 40mph at 6k RPM and you are not at WOT, then you probably have a ton of prop slip as well as the wrong pitch. I recently got a new prop for my 22’ Mako center console. I PROMISE you want to discuss this with a good prop shop. They will help you get the absolute best performance for the way that you want to use the boat. You will be disappointed if you just take someone’s suggestion and just go buy a prop. This is something that you want to do right the first time.

Call Ken Reeves at Prop Gods in Sarasota Florida. He will get you fixed up. (941) 735-5808

The prop may be slipping on the hub. As Miles said, get it checked out before you make any other decisions.

I sure do appreciate everyone's input. When I purchased the boat the first thing I did was put it in the shop. I had the mechanic go thru everything. It ended up costing me a pretty penny but to me its worth it. Im going to research some videos on props slipping and give that fellow a call down in Florida. Thanks again everyone

Check these guys out. Very knowledgeable group here also.

https://seaproforum.proboards.com/

could be prop slippage, ( when the hub slips on the propeller). but usually this happens as soon as you give it the beans,,, its under the most torque when its under the initially load. as the boat comes up on plane, the resistance on the prop lessens.
As was stated, the very first thing u need to do is find out what the motors wide open throttle max rpms are for your motor. until u know what that is, you shouldnt make any changes..

when you say prop slip,, do you mean the prop is slipping on the hub? or do you mean the prop is cavitating?

Old test reports of a Sea Pro 218 w/ yamaha 150f show around 42mph top end. You may very well be propped correctly as it is. Just because you have a little throttle left doesn't necessarily mean the motor is going to rev much higher depending on the load.