Recommended rpm

[kraetzer]

I have a 200 merc optimax and if I run it at the recommended rpm (~5000 to 6000) I get around 50mph out of it. I can rev it up to over 7000 and get about 65mph. How limited should you run your engine in the high rpm's or should you do it at all?
Thanks,

[gt1984]

Your prop is to small. What are you running? You should be able to go WOT and be at around 5800rpm.

[chf8500]

Need to know a bit more info, 7K should scatter your 200 bad, sounds like maybe a wrong setting on your tach. 65mph on most 200 hp motor/boat combos comes around 5800 rpm with a 24/25p prop. check the little rotary screw on the back of your tach, probably on the wrong pulse

[kraetzer]

I'm running a 24p fury. I also didn't notice the high rpm's before so it could have something to do with the screw chf8500 mentioned. What pulse should it be and is this a easy fix?
Thanks for all the help,

[gt1984]

Did you figure it out? If it is not the guage, let me know. I have some other suggestions that will get it fixed.

[kraetzer]

Not yet. I crawled under the console but I'm not sure how I could change the gauge. I also just saw that the rpm shows 1000 right now (on the trailer ). Do I have to look for a screw with which I can adjust the needle or is it something like setting it to a different gear?
Thanks again,

[gt1984]

First, don't adjust anything. Do you have a set of rabbit ears? Place them over the water intake of the lower end, turn the water on and turn your motor on. Keep it at idle. The RPMs should be around 600-800. If that is the case, then it is set correctly and when turned off just rests at the 1000 mark. If it shows 1700 at idle, then it needs to have the screw adjusted so that idle speed is around 600-800. This probably is it for when you adjust it down puts WOT at 6000. You need to change your prop to a 25 and that will cause it to come down another 200-300 RPM's and put you at 5700-5800. It will also increase your top end speed several mph. Give me your specs and I can help you fine tune it.

Height - Center of prop in relation to pad. (i.e. 3" under)
Jackplate setback
Brand and model of boat

[drew]

If your speed is accurate (GPS) you should be turning 5400rpm at 65mph with a 24" prop and a 1.87 final drive. The only way you could spin 7K would be if you had your engine set too high. The tachometer screws usually don't turn or come out of adjustment on their own. I have seen tachs that read incorrectly because they had built up some corrosion on the switch contacts. Remove the mounting bracket from the tach and slip it out of the dash. Then rotate the screw back forth a few times and return it to the original position. This will clean off the contacts. BTW The tach if set incorrectly will be off by a percent not a constant. 5400/7000 is 23% at idle it will read 23% high, 900X1.23 =1100rpm.

[gabuelhaj]

Loose battery terminal lugs will cause false tach readings. Make sure your battery terminal lugs are tight in addition to jarring the screw setting on the back of the tack. On this screw setting, only go back and forth a couple of times and NOT all away around. I think it needs to be set to 6P so make a note of its current position before touching it.

Good luck!

[kraetzer]

Thanks for all the pointers. Will be on the water on Saturday checking everything out.
Thanks,

[kraetzer]

I checked my battery lugs and all of them were tight. Idle shows 1200-1300 rpm. I don't have a jackplate and run the 200 merc optimax on my nitro z-8. What's the best way to measure prop to pad?
Thx,

[mr.bass91]

If the tach readings were normal until recently it sounds like the connections on the back of your tach to me. I have had the same issue. Once in awhile my tach will read like 500 over. I tap on the gauge a little and it goes right down to where it should be. The connections for electronics in boats get corroded easily.

[gt1984]

If you do not have a jackplate, the prop/pad measurement is irrelevent as your motor is fixed to the transom. All you can do is trim to maximize rpm/mph. Prop size can change top end and holeshot approximatly 200 rpm. If you run a 24 and change to a 25, your rpms will go down 200 or so and your top end will increase as long as it still gets you out of the hole. Also, some hulls respond better with a 4 blade then a 3 blade and will also change the rpm and performance by another 150 rpm.