97 z222 5.7L RPM advise
 

Can any one chime in on what they get for WOT with a 19P prop with similar boat please. 4100 is what I get 42mph. full fuel 4 adults and coolers.

Re: 97 z222 5.7L RPM advise
 

The 97 brochure states 46-52 MPH with the 5.7L. My 99 Z202 is supposedly about 1000 lbs lighter and does 55 MPH (4500 RPM) with one person aboard and full tank and 24" duo-props.

Re: 97 z222 5.7L RPM advise
 

First question might be where was your trim? You won't get full speed and RPM unless the trim is near optimal. But WOT RPM is supposed to be more like 45-4800 rpm with the correct pitch prop. A 19" is near the low wend so you shouldn't have much trouble reaching full RPM I think.

Re: 97 z222 5.7L RPM advise
 

Trim is right and played with. 19p is 4100rom 42mph. 17p is 4600rpm plus 45-46 mph. Any ideas. This was a windy day this week. 2 adults 1 child full tank of gas.

Re: 97 z222 5.7L RPM advise
 

The 5.7 should easily push your boat to 4800 RPM's with a 19" prop. Even with a full load of people and gas I would expect 4600-4700. There are so many variables when tuning a boat for speed. Most of those variables are either related to the hull and weight of the boat or they are related to how the engine is applying force or propulsion to the boat via the prop. With that said, the boat/hull and the engine performance are closely tied. By trimming the outdrive you are reducing wetted surface thus creating less drag on the boat which theoretically should increase speed.

As I'm sure you know, a smaller pitch prop has the same effect as a lower gear on a car. If you want to achieve a certain speed then math can be applied to determine what is needed to reach that speed. By using a 17" prop you are lowering the amount of power required to reach a certain RPM (4600 in this case). A 19" prop with a 1.47 gear ratio at 4100 RPM and a .15 slip differential should be about 42MPH which aligns with your findings. The fact that you're still not able to achieve max RPM's with a smaller prop is concerning. That engine should spin the crap out of a 17" prop.

There are a couple possibilities that are common for this scenario. The first is you have water in your hull. This can add an enormous amount of weight to the boat and cause performance issues such as you are describing. Check for soft spots in the floor or hull or go weigh the boat at a stockyard or city dump. This should tell you pretty quickly if there's unexpected weight. The second possibility is the engine is not able to apply sufficient power to reach max RPM's. I would start with a compression check and inspection of plugs etc. Either way it sounds like there is something significant going on with your rig.

If you were trying to eek out a couple more MPH then there are tweaks you could make to close the gap like trim tabs or shifting passengers to different parts of the boat. What you're describing is way out of spec for that engine and boat. The fact that you reached 4600 with the smaller prop pretty much eliminates some sort of restriction in the ignition system.

Re: 97 z222 5.7L RPM advise
 

Sorry, I didn't actually answer your original question. My 202 is about 300 lbs lighter than your 222 and I have the pre-vortec motor. Your boat should have the vortec version of the 5.7 which is about 20 to 30 more HP.

My boat does 49-50 with a 19" prop and around 52 with a 21" prop. As I mentioned in my first reply, your motor should have no problem pushing that 19" prop to max RPM. Even a 21" prop should work fine once you're on plane and at speed. I only use a 19" because we do so much skiing and wakeboarding and it gives me a better hole shot and better speed control for a big wake.

Re: 97 z222 5.7L RPM advise
 

Scottie,
The 97 brochure shows the 222 or Z222 weighing 3500 lbs. The 95 brochure shows your Z202 at 2800 lbs. That's a difference of 700 lbs, not 300 lbs. Where did you see the 300 lbs difference?

Re: 97 z222 5.7L RPM advise
 

Gary,
You're exactly right on the weights listed on the brochure. I was adding about 350 lbs to my boat because of the wakeboard tower, two heavy amps and some bigger than necessary sound system. Also I thought the listed weight for the 202 was with the 3.0 motor. Either way your point is well taken and I should have explained the weight difference.

Re: 97 z222 5.7L RPM advise
 

No soft spots in floor or hull that I'm aware of. No water in hull. I can get over 4600 with 17p. I read on this site flame arrestor can get plugged. Can that be? Should I run without it? Just to see. Motor runs starts great. I can do comp check. What should each cylinder be?

Re: 97 z222 5.7L RPM advise
 

Before you go to the trouble of a compression check.. which if low would indicate an unhealthy motor... I would clean the flame arrestor which could effect air flow and maybe replace the fuel filter. A lack of either air or fuel will bring the power down on ANY engine. Those are the simplest of things to look at and the easiest to remedy, and besides these are routine maintenance anyway.

When you have the flame arrestor off, also make sure if the throttle is set to WO you see the butterfly in there go WO. It could even be from movement in the linkage.

I've experienced power loss (not on my boat) from air restriction and low fuel flow/pressure or a not WO throttle butterfly. It will run fine for the most part until you ask for full WOT performance and then it may just feel a bit anemic and not able to achieve peak power.