What does the in the seat feel of a blowout feel like or being close to it.
At higher speeds and tweaking trim and engine height for top speed I feel like the stern gets slippery or skates around in short quick movements. I don't want to be pushing the limits into a bad situation.
Hull: 07 TR-20XHP
225 PROXS
gen1 tm
1B380805
Sounds like crabbing. Blowout is sudden. You won't be guessing if it happened or not. Sudden bow drop and hopefully you don't make a quick right turn.
Crabbing is caused by the prop losing bite, then regaining it. Lower your prop or have it worked...possibly both.
"Better to remain silent and be thought a fool than to speak out and remove all doubt."
PTP was likely too high.
What you are feeling sounds like you are approaching the boundary. At true blowout, two things happen. First the prop loses bite, and second the bow drops. Now you have a serious problem. When the prop loses bite, it is STILL spinning. Clockwise looking from the rear. Imagine you removed the prop, put a 14" diameter wheel on it, and set it on the ground in the parking lot. Rear end is going to to the right quickly and violently. That hurts. Second, a boat on the ragged edge of the performance curve is always crabbing down the line of travel because that circular prop rotation turns into an angular component to the thrust line. As a result, you have to steer to the opposite direction to go straight. So the centerline of the boat is slightly off the direction of travel, and when you drop the bow, you get what used to be called a "bat-turn" (as in the old BatMan TV/comic book days). Either of those two things is highly problematic because either results in a sharp turn. Which usually results in an ejection if you are not ready, or lots of bruises if you are ready. If you feel that loose feeling when trimming an Allison, for example, you better get the trim back down a touch about 2 seconds ago, that "waggle" is a warning of pending disaster.
2008 Bass Cat Pantera Classic
2014 Mercury Pro XS 200
Great advice....Originally Posted by OldTimer57
Indeed great advice.
I calibrated my JP gauge in relation to what PTP height is and put them in my phone to reference. I have found that between 12 and 13 on my gauge is 3 and 2 3/4 respectively. It seems to like the 13 at 2 3/4. I have seen no drop in WP at that height. I feel like I am close to getting all she has. Like said wanting to learn ( the good way ) what to expect as to not cross the line. My question is. If the prop is losing bite would not my Rs go up and down as it loses and bites again? I turned 76 mph and still had nearly 200 rpms before I got 6k. The 26 tempest may be just a bit big. I have not at all felt like it was getting too loose to be in danger yet. So in conclusion this crabbing im feeling is not something loose or broken. Just a characteristic of having it on the pad and pouring it to it.
Your NOT going to blowout at a PTP of 2.75"-3.00".
So from all íve seen in the past I can trim and raise engine height until a drop in water pressure is seen? Safely.
I would not say "never" to the blowout at 2 3/4. I had a 92 astro with a "warmed up" 2.5 liter that would break 90. And I blew that sumbitch out at 92 mph and my entire right side was black from banging into the side of the boat. And I was somewhere in that 2-3" range when it happened. A left-hand turn to end all left-hand turns. Did it once in that boat and twice in an alley XR. That was my lifetime quota for such things. A lot about what can happen depends on the boat, motor, prop, lower unit, bottom of pad, phase of the moon, color of the hull, etc...
Edit: That 2.5 did NOT have a CLE gear case. Makes it MUCH easier to blow it out at those speeds, something I did not know at the time. Something I won't ever forget either...
Last edited by OldTimer57; 11-08-2017 at 09:49 PM.
2008 Bass Cat Pantera Classic
2014 Mercury Pro XS 200
I stand by my "never" comment for the OP @ 2.75"- 3" PTP for his Triton Hull......
His speed can't get much higher than 76 MPH, maybe 77 for his hull.
His 3"- 2.75" PTP is TYPICAL for alot of TRITON owners.
He's running a large diameter Tempest Prop.
@ those PTP Heights the prop is well into the water.
He has a Torquemaster Gearcase.
He's never going to hit 80 MPH, unless he's on a highway.
Last edited by Savage; 11-09-2017 at 06:29 AM.
You raise it until you.....
Lose safe Water Pressure.
Stop seeing a MPH increase, but RPM's continue to Rise.
Your prop will definitely be slipping at any setting higher than a 2" PTP.
Last edited by Savage; 11-09-2017 at 06:33 AM.
Thank you very much gentleman. No substitute for experience. I'd rather learn from past experience than my own. Lol. I feel good about it and like said. I was trying to see if she'd do 80 but doubt it will. Definitely not properly set up for all around performance. I do get curious when fuel gets low and I have a light load. All said and done will probably go back to a 25 for best all around. With air temps cooling I'll probably try to find those 200 rpms and stay below that 2" but im satisfied.
Would not disagree with that unless he has modded the motor. My XR6 would never blow out in stock form either. But once I cranked it up with dual plug high compression heads, 7 petal reed intake, really big carbs, etc, I learned all about blowout and why that small gear case was not what was needed at those speeds.
2008 Bass Cat Pantera Classic
2014 Mercury Pro XS 200
Your just getting the hull loose which means fast but I don't think you'll hit 80 with a 26" prop.
I agree- not likely this setup is ever going to see the 80 MPH mark.
That being said... I've learned to be careful about saying "never". Especially since I saw it happen once.
If there's an abnormality in the gearcase (leading edge damage, or trailing edge of cambered skeg improperly machined) it CAN occur.
Best advice I have to offer the OP is: Don't let your hands and feet write checks your backside can't cash. If you feel UNCOMFORTABLE, you need to back off a bit, and give yourself some more seat time.
Every different boat has some different handling characteristics, and it's never wise to push the limits of your experience.
Just the honest opinion of someone who's used up his two "free passes".
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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