Safe to go WOT?

B

brstephe

New Member
Jan 27, 2011
33
Atlanta, Lanier
Boat Info
2004 Sundeck 220
Engines
5.0 MPI BravoIII
Don't know if this belongs here or Gas/Engine. Don't see this specific question on search. Wondering if I'm OK to open up the engine to see what it will do. How long to sustain or when to back off? I'm so used to babying it and so far always had others onboard to tube... roughly 3k to plane and sometimes "fast" is 3.5k rpms. I think I recall this being nothing more than about 20-25mph. Wondering what thresholds I should look out for with WOT, i.e. will engine rev and blow at some point or just run max rpms sustained? Am I running a danger of trying to get it up to X rpm?

Typical 260hp 5.0 MPI BIII setup on a 220SD. Factory pitch I'm sure. What to expect for rpm and mph too?
 
Specs say WOT is 4,400 - 4,800 RPM. While running around at wot all the time is not recommended, there is nothing wrong with winding it up every once in awhile to see what she'll do. Just watch the tach, and pull back if it looks to be edging above 4,800. With your boat/motor setup I would suspect WOT will put you in the low 40s for mph.
 
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I run my boat up to WOT twice a season for just a couple minutes - typically after I add fresh fuel in the spring/summer and then toward the end of the season. Then at WOT I watch the RPM's to see if my engines are synced and then I watch that the oil pressure is holding. Last season - I never opened the boat up. But - my boats have always needed to be between 3200 and 3600 rpm's minimum to stay on plane. I try to keep the boat running at around 75% of WOT for cruising on plane, when getting on plane - the engines will hit about 4000 rpm's and then I pull back to about 3650 to 3750 rpms - my boat runs WOT at 5000 RPMs. Then when I idle around - I like to be at about 1600 rpm's. When I owned my 2 previous boats WOT was around 4400 rpms and I would cruise at 3200 rpm's. I opened the smaller boats up a few more (5) times a season - but still not for a long duration. I also watch the temp gauge and water pressure gauge. I can display all of my gauges on my GPS.
 
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When you open it up trim it out as far as you can before it ventilates. Watch your gauges max rpm for 5.0mpi is 5000 rpm. When I plane off I often will go wide open to jump on plane then back off to 3000 rpm.
 
I thought a blowout was what happens when you get the mechanics bill. Requires changing the drawers? And sometimes makes you palpitate.

Good input folks. I just didn't want to introduce too much excessive wear or tear if winding it up. The 4800rpm is a good guide. What would happen if you just hammer down and left it.... would you over rev and blow something or is the engine/rpm regulated in some way? Not that I'm trying to be a racer, inquiring minds just wonder.
 
I don't know about 2004 models but my 2010 4.3mpi has an overspeed limiter which will not allow the engine to rev past 4950 rpm's. At that point you can feel the engine hesitate and an alarm sounds. On the 5.0mpi this may happen at a higher rpm as the engine is rated at 4600-5000 instead of 4400-4800.
 
You may never hit the rev limiter. The main thing as you put the hammer down is to watch the gauges and see how your boat reacts. Every boat is different and going full throttle for a period of time is not going to hurt anything as long as oil/water pressure are OK and you don;t over rev the motor. My last boat (bought new) had a 200HP outboard and after 12 years and probably 1400+ hours it ran like new. Nothing other than normal service was done to it and I ran it full throttle and trimmed up probably 50% of the time.
 
brstephe said:
Don't know if this belongs here or Gas/Engine. Don't see this specific question on search. Wondering if I'm OK to open up the engine to see what it will do.
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Wow, I full throttled my boat on the first two trips out to see how it did and felt to me, and to show off to my passengers. :smt001

Guys have already told you what to look for. Have fun! I don't go past crusing RPM's much really (3600rpm) as I hate to actually see the fuel gauge moving downward that fast, but this past weekend I went up to 4200rpm for a few minutes to get ahead of a boat that was parallel to me for several miles and the river was beginning to pinch in. It was fun as he was in a smaller bowrider and I disappeared in front of him. :smt001 Engines purred like a young kitten...
 
I second Gunns statement. I forgot to add that in our boats we don't run full throttle too much because it hurts to actually watch the speedo go to 48MPH and actually seeing the fuel gauge moving towards empty.
 
My days boat when he had it a 1986 Arrow Glass Bow Rider with an OMC 135 had a rev limiter. Besides, you would more than likely float the valves before you did damage.
 
Bucit said:
I second Gunns statement. I forgot to add that in our boats we don't run full throttle too much because it hurts to actually watch the speedo go to 48MPH and actually seeing the fuel gauge moving towards empty.
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so which guage wins the race ???
 
Bucit said:
I second Gunns statement. I forgot to add that in our boats we don't run full throttle too much because it hurts to actually watch the speedo go to 48MPH and actually seeing the fuel gauge moving towards empty.
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You can run 48mph??
 
Bucit said:
45-48 depending on weight and sea conditions.
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I must definetly have something wrong! My boat won't plane loaded without full tabs, everyone elses will....my boat tops out about 42, and that's with a bottom with no bottom paint and looks like new, and everyone has more topend:huh: You have me curious now:smt101:smt021

Edit: I should add that she runs perfectly when she runs!
 
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I have a problem getting on plane too with a full laod of full, water, heavy passengers and full coolers. I notice when I hammer down that the port motor lags behind by 300-500 rpms until it hits around 3200rpm's and then it catches up. I'm sure this is hindering the planning but I'm not going to do a tune up until next year when I replace the risers and manifolds.
 
Bucit said:
I have a problem getting on plane too with a full laod of full, water, heavy passengers and full coolers. I notice when I hammer down that the port motor lags behind by 300-500 rpms until it hits around 3200rpm's and then it catches up. I'm sure this is hindering the planning but I'm not going to do a tune up until next year when I replace the risers and manifolds.
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Hate to keep up the hijack...lol My port is the same, it has a new tune up!!
 
MaddyDean said:
float the valve???
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When an engine is over-reved, the camshafts are spinning fast enough that the valves overcome the pull of the valve springs and "float" off the camshaft (or rocker or whaever). In a non-interference engine it isn't necessarily a catastrophe. In an interference engine (meaning the pistons occupy the same space at the top of the bore as the valves do when they are open), it is bad news bears as it can lead to bending a valve/snapping the head off, and the ensuing carnage.
 
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