Engine cutting out

[diggerglp]

Once again I come to the experts on this forum for help. I have a 2000 21V with 350 Mercruiser Tour Ski engine. Just had it tuned after buying it and took it out Sunday (ice just off the lakes). Motor ran well at all speeds except at WOT and then it would cut out. It has new plugs but I know the plug wires were not changed out so thinking this may be the problem at high RPM.
I don't think they changed out the fuel filter so that might be a possibility too. Maybe the gas but I did add conditioner for the winter and added new gas. So any ideas would be appreciated.
And I can't locate the fuel filter - can you direct me to its location.
Thanks for the help.
65 (woo hoo) here today so going to take it out again and see what happens.

[chpthril]

What was the RPM at WOT when it was cutting out? Wrong prop to have it hitting the rev limiter.

[boatwakes]

Fuel filter is located at the actual front of the engine, port side of the boat right next to and slightly above the raw water pump. It may be covered by a black plastic housing. Remove that stupid thing and leave it off after you change the fuel filter.
What kind of cutting out do you mean? Like CHP said, rev limiter is possible but backfiring, chugging, popping and snapping, noise descriptions please, if any.

[diggerglp]

WOT was 5000 RPM with a Acme 537 prop.
The cutting out is like it loses power for a second and then kicks back in but will continue to do this off and on until I back off the throttle. After backing off the throttle just a bit it runs great. So clue me in on what the rev limiter is and does?
Also today I was getting a high pitched buzzing sound occasionally when I was idling around. Would stay on for a while and then go off. Any help on what this is, I am thinking a warning buzzer but it is not very loud and nothing looked like it was overheated, low oil, etc so not sure what it is for.
Thanks again for your help.

[boatwakes]

This is from the Mercruiser book:
Over-speed control
"The ignition module will prevent the engine speed from exceeding a preset limit by stopping the spark. The over-speed limit is set slightly higher than the top end of the rpm range. For example, if the recommended range is 4600-5000 rpm, the overspeed limit would be set at 5100 rpm. When rpm reaches the limit, spark is turned off until the engine rpm drops down to a RESET rpm, which would be approximately 4750 rpm for this example. At this point, spark comes back on."
This is the rev-limiter, designed to save your engine if you launch the boat and the prop gets out of the water while under load. Your WOT seems slightly high too. I would just recommend you stay out of the top end of the throttle range.
The high pitched buzzing was most likely the fuel pump, located on the starboard side down by the stringer. You can thank the Democrats and their ethanol blended fuel for that as you replace said $485 part when it fails.

[chpthril]

When it starts cutting out, does it seem rhythmic? I agree with boatwakes, 5K is a bit high. I guess I should I asked before, but what was the boat speed at WOT? If you are able to get over 40 MPH before hitting WOT, and the suspected rev limiter, im not sure I would worry too much about re-prop'ing unless you're a foot'r or you dont like the hole-shot or it struggles to hold speed when loaded up with ballast.

Do you know the drive-train ratio? Who put the 537 on?

[diggerglp]

The cutting out is pretty rhythmic. The boat speed at WOT is 48 mph at 5000 rpm. How would I check to find out the drive train ratio. The marina where I had it serviced put the prop on. When I bought the boat it had a 4 blade SS (couldn't read the numbers to see what size it was) that was dinged up pretty good so that's why I got the new prop and was told by the dealer I got it from that the 537 was the recommended prop for this boat and engine.
My daughter will use the boat for slamon skiing, wakeboarding and wake surfing and it has ballasts installed but haven't used it for this yet so can't comment on hole shot or how it handles with ballast loaded. It does seem to jump out of the hole though without any skiers, etc.
So it sounds like the rev limiter is going off above the 5000 rpm and we should stay below that. Are we OK with this prop? The boat will be going to Montana and used at about 6500 ft elevation.
Again thanks for your inputs.

[whitlock87]

at what max rpm will it run with no issue?
if around 3000, then i would look at a fule flow issue.

[boatwakes]

Digger, your requirements of the boat will dictate if the prop is the right one for you. If you want more speed, you can do one of two things: reprop with something that has another inch of pitch in it or rework the prop that's on the boat to put more cup or another inch of pitch. The rule of thumb is: every inch of pitch pulls about 150-200 rpm off the top end and every inch of diameter is equal to 1.5-2" of pitch. From the WOT numbers you're showing, you could use 1-2" of pitch increase or just another inch of diameter and no pitch. But, you're taking it up to 6500' so altitude will now be a huge variable. I would suggest you stick with the prop on the boat for now and see what WOT is at altitude and then pull some skiers, pull some boarders, experiment with weighting and find out what the boat does first. Then determine if you want it to do anything different and if so, go from there. -Good luck.

[diggerglp]

Thanks BW for all the info. Think I will stay with the 537 and let my daughter try it out in Montana before we do any changing. Will just tell her to keep it below the rev limiter which is plenty of speed.
Side note, I was in CA for 37 years up in the Antelope Valley. Coached and taught at Palmdale HS. My son went to LB State. Bought my Skeeter at the Long Beach boat show.
Fished and boated at Pyramid and up at Nacimiento a lot.
Thanks again, Digger