Trying to figure out if my outboard is mounted too high. Currently have a 23p bravo lt on the boat that is getting up to 6300rpm with a 200HP L4 verado. Boat is only hitting 50mph, with a 2.08 gear ratio is calculated somewhere between a 23-25% slip rate. The boat also porpoises pretty badly without a hydrofoil on it. I don’t have any cavitation. Pretty sure it’s mounted too high just want confirmation basically.
If you have a jackplate, lower the motor a half inch and run it. If it improves keep adjusting until you find the sweet spot.
Is this trimmed all the way up? Does it improve if you trim down? Sounds more like a way out-of-spec prop to me to give you results that are that bad. What kind of boat is it?
2011 Skeeter ZX225
225 Yamaha HPDI Series 2
Minn Kota Ultrex 112 52"
Console: HDS 16 Carbon
Bow: HDS 12 Carbon, Solix 12 G2, Mega 360, Garmin 106 SV, LVS 34
It’s a Tracker Targa 1900 deep V walleye boat. Those numbers are with the motor fully trimmed out. Trimming in doesn’t really seem to change much. Boat is on a manual jack plate. Previous prop I had on it was a 21 Pitch Rev 4 that ran 51MPH at roughly 6200 RPMOriginally Posted by DrewFlu33
If it's porpoising I'd say it is to high.
Mercury 250 proxs 2B115089
Have you measured prop to pad for reference?
2006 Triton TR-21 XD, Mercury 225 Pro XS, S/N 1B287870
And trimmed up too much. The engine could *both* be mounted too high and trimmed too much. If it’s mounted too high, you might not see any [or little] difference in performance between full and half trim. And burying the engine at zero trim might give you a solid hookup on the prop, but with no leverage angle might not raise the bow enough to increase speed. This is why both engine height and trim angle are important to optimum high speed performance. I have no experience with a Bravo on a deep V boat, but bow lift is more difficult to obtain than on a typical bass boat, so a prop with very good lift is also important.
John Clark — Findlay, Ohio
Tayzak15,
This is very good advice and easy for you to measure. There is a sticky in 1 of the forums which shows how to do it, which is basically placing your boat on a flat area and level the keel or pad. Take the measurement from keel/pad to ground. Level your motor anti cavitation plate, and measure from center of prop to ground. Now, take the first measure and subtract the second which result is the center of prop to keel/pad measure. Good starting point is 3.5" and adjust 1/4" at the time to get to your best performance measurement.
BTW, make sure that your prop has been blueprinted and balanced for best results
does it make a difference If my motor is on a setback transom and on a 8 inch jackplate?
Too high usually results in low water pressure, prop letting go in turns, or lack of bow lift are usually the telltale signs.
Sometimes porpoising is caused by too much bow lift and dropping the motor will give it more bite and make it worse. That deep v isn't going to run like a pad hull, carrying the nose high. If you have a jackplate, I'd definitely try moving the motor up and down. Might be the wrong prop altogether, or just need some additional cup.
No, my motor is on a 10" JP that is set at 2 7/8" P to P. Follow that steps I wrote for you and you should have your P to P measurement.
BTW, your RPM seem to be inline with what Mercury calls for your motor 5600-6400 so your prop pitch is fine at 62-6300, but the prop specs could be off if it has never been blueprinted and balanced.
Im turning 6300 RPM, but my slip rate is almost 25% which seems like a lot! The prop did have some dings and was sent in for repair this spring.
I am sure that is just paper calculation, but it would improve if you send your prop to Mark Croxton for tune based on current running numbers and P to P.
Last boat I was in with a Verado mounted too high blew out & flipped. One thing I do remember is a very high rooster tale
That is incompetent operator over trimming to the point that the motor was into tilt mode. Best thing for your motor is that owner learns how to operate not only the boat but the gauges in the boat telling him what is going on during operation. How many times people ask about bringing up a JP, but their water gauge don't work or don't have 1.
The Targa most of these board visitors can't help you with. The best answer is some slippage and the engine could be mounted too high, which would give you excess steering torque even on a Targa.
Yeah I kind of figured. I just know there’s a lot of traffic on this site so doesn’t hurt to ask. I dropped my motor about an inch and going to try running a 21pitch bravo FS a friend is lending to me rather than the 23pitch bravo LT. Hopefully I see some improvement at least in the prop slip percentages.
That’s a pretty good speed from a 4 cylinder verado and a 19’ deep v.
Thats your opinion without actually being there. I have pictures of how the motor was trimmed. Heavy motor with built in setback jackplate factory mounted incorrectly = bad newsThat is incompetent operator over trimming to the point that the motor was into tilt mode. Best thing for your motor is that owner learns how to operate not only the boat but the gauges in the boat telling him what is going on during operation. How many times people ask about bringing up a JP, but their water gauge don't work or don't have 1.
So, are you saying that because it is a aluminium Targa and my fiberglass Viper Cobra, there is no correlation on how to find the best operational performance by using the keel/pad to prop shaft measurement to achieve it and eliminate variables by starting fresh at a commonly suggested 3.5" making corrections 1/4" watching water pressure and RPM/speed??
Targa has a 35* deadrise at bow and 20* at transom. My Cobra 201DC has a 42* deadrise at bow and 26* wide V pad rear running 10" JP, that after much test and tune with a properly tuned prop, is set at 2 7/8" P to P, though I started at 3.5" as suggested by Larry Nickels. Though you will say that these 2 boat have little in common, the same hydrophysics apply giving them their individual limitations. Think of it this way, IMSA runs 3 or 4 very distinctive classes of race cars on the same road coarse, yet the same kinetic physics apply to all of them which give them their individual limitations. Hence, certain chassis setup geometry can be shared as a base median point when discussing car reaction in certain turns or race conditions.
BTW, I do agree with you that an engine set too high will give you a crap load of torque steer and bad characteristics.
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