PRO XS V8 4 STROKE TRIM/TILT

[JAZII]

SN# 3B040668

Question for owners of Pro XS V8 4 stroke engines with the old trilobe style pin.

Does your trim/tilt bleed down to the trim rods if you are in the tilt section while power loading your boat on the trailer?


My 250 Pro XS V8 4 stroke does not bleed down to the trim rods if I have it in the tilt mode and power load.

Why am I asking this question? My threaded pin fell out on a 180 mile round trip tournament about 20 miles from the ramp. Before I realized something was wrong, I was able to OVER TRIM into the tilt range with no trim feed back to the engine PCM. At some point my trim flashed from 0.0 to 15 on SC Tach and engine went into guardian mode hard then right back to 6000 rpm in a flash. My boat did a slight bow hook when it went into guardian then almost jrked the wheel out of my hands when the rpm jumped right back to 6000 rpm.

[fishnfireman]

Good question !
One I can't answer till next week.. Leave my boat at lake Amistad in the winter.

[thommo59]

Yes mine will lower until it hits the trim rams, this is normal. Your situation is different because of that pin issue

[JAZII]

I know the old style trim/tilt bleed down through valving in the unit itselft, nothing to do with the pin.

I was able to trim into the tilt range under full load on plane at 78-81 mph. My boat normally only runs to 76 with the new 4 stroke best ever.

The valving in the trim/tilt unit should never let you over trim into the tilt range under full load. I was asking the question as to find out if anything changed in the trim/tilt with the redesign and threaded pin.

Yes mine will lower until it hits the trim rams, this is normal. Your situation is different because of that pin issue

[Jasonrs]

Mine will only trim to the top of the rods under load. Its around 7 on my smartcraft for my particular setup (edit: i have the threaded style pin)

[JAZII]

your smart craft guage needs to be calibrated. It should read 10 at max trim.

Mine will only trim to the top of the rods under load. Its around 7 on my smartcraft for my particular setup (edit: i have the threaded style pin)

[Jasonrs]

your smart craft guage needs to be calibrated. It should read 10 at max trim.

Good to know, thank you!

[JAZII]

I have confirmed my tilt will not bleed down to the trim rods when power loading. I could push the truck up the ramp if I stay in the throttle without it bleeding down out of the tilt.

Just to be clear. I have the new design threaded pin. No idea if anything was also a running design change with tilt/trim unit for production of my engine. With proper sensor feed back, under on plane running load, it will not go into tilt(this is proper operation).

[EuropeanAM]

Pin design does not affect this topic.

You essentially have a system that has (due to threaded pin failure) bypassed the sensor input information to the PCM. This the PCM may permit normal RPM's to be applied, even if the prop was completely out of the water (this would not normally occur).

"Push truck up ramp" is really a pretty broad scenario. <EDIT: Over-Trim RPM limitation is fully and solely ELECTRONIC (and controlled by the PCM)>

Trimming that far up with most bassboats (at high speed) would usually result in handling difficulties, drastic increase in prop slip (or complete prop blowout).

Need to address the obvious problem (with your dealer) first.

[JAZII]

Don,

My threaded trim pin has been replaced. My trim/tilt readings are correct on my SC tach and dash guage. Trim/tilt has been reset with G3 Mercury computer.

My tilt will not bleed down under any RPM and I have not seen any RPM limit up to 4000 RPM while power loading TRYING TO MAKE IT BLEED DOWN.
Set at 15 tilt range and floor the hot foot tilt will not bleed down to trim rods, SC Tach tilt will stay right at 15, realistically push the truck up the ramp if truch driver doesn't stand on the brake.

My engine WILL NOT over trim into the tilt range while on plane or starting from 0 trim. (proper operation)
But at idle, set trim/tilt to 15 and punch throttle, no bleed down and no rpm limit observed.

Not looking for a debate, looking for info if anything was changed in the trim/tilt at the time of the threaded pin change.
The operation of this SN# 3B040668 engine trim/tilt is acting different than any other Mercury engine trim/tilt I have ever owned.

Most dealers are swamped around here, also very limited experiance with them working on the high performance boat/4 stroke.
If they can't make money, they have no time to investigate anything any further than hourly Mercury rate.

Thanks for your dedicated time to this forum.

Pin design does not affect this topic.

You essentially have a system that has (due to threaded pin failure) bypassed the sensor input information to the PCM. This the PCM may permit normal RPM's to be applied, even if the prop was completely out of the water (this would not normally occur).

"Push truck up ramp" is really a pretty broad scenario. In order for the relief mechanisms to function, high-thrust of 2800+ RPM's, with a good bite of the prop in the water would have to occur.

Trimming that far up with most bassboats (at high speed) would usually result in handling difficulties, drastic increase in prop slip (or complete prop blowout).

Need to address the obvious problem (with your dealer) first.

[Blue Steel]

Don,

My threaded trim pin has been replaced. My trim/tilt readings are correct on my SC tach and dash guage. Trim/tilt has been reset with G3 Mercury computer.

My tilt will not bleed down under any RPM and I have not seen any RPM limit up to 4000 RPM while power loading TRYING TO MAKE IT BLEED DOWN.
Set at 15 tilt range and floor the hot foot tilt will not bleed down to trim rods, SC Tach tilt will stay right at 15, realistically push the truck up the ramp if truch driver doesn't stand on the brake.

My engine WILL NOT over trim into the tilt range while on plane or starting from 0 trim. (proper operation)
But at idle, set trim/tilt to 15 and punch throttle, no bleed down and no rpm limit observed.

Not looking for a debate, looking for info if anything was changed in the trim/tilt at the time of the threaded pin change.
The operation of this SN# 3B040668 engine trim/tilt is acting different than any other Mercury engine trim/tilt I have ever owned.

Most dealers are swamped around here, also very limited experiance with them working on the high performance boat/4 stroke.
If they can't make money, they have no time to investigate anything any further than hourly Mercury rate.

Thanks for your dedicated time to this forum.

Thanx Jazz for pursuing this issue.

[EuropeanAM]

Don,

My threaded trim pin has been replaced. My trim/tilt readings are correct on my SC tach and dash guage. Trim/tilt has been reset with G3 Mercury computer.

My tilt will not bleed down under any RPM and I have not seen any RPM limit up to 4000 RPM while power loading TRYING TO MAKE IT BLEED DOWN.
Set at 15 tilt range and floor the hot foot tilt will not bleed down to trim rods, SC Tach tilt will stay right at 15, realistically push the truck up the ramp if truch driver doesn't stand on the brake.

My engine WILL NOT over trim into the tilt range while on plane or starting from 0 trim. (proper operation)
But at idle, set trim/tilt to 15 and punch throttle, no bleed down and no rpm limit observed.

Not looking for a debate, looking for info if anything was changed in the trim/tilt at the time of the threaded pin change.
The operation of this SN# 3B040668 engine trim/tilt is acting different than any other Mercury engine trim/tilt I have ever owned.

Most dealers are swamped around here, also very limited experiance with them working on the high performance boat/4 stroke.
If they can't make money, they have no time to investigate anything any further than hourly Mercury rate.

Thanks for your dedicated time to this forum.

Page 5B-6 of the Service Manual for your engine states:

The trim cylinders position the outboard at the desired trim angle in the 20 degree maximum trim range. The system will not
allow the outboard to be trimmed above the 20 degree trim range when the engine RPM is above approximately 2000 RPM.

The outboard can be trimmed above the 20 degree maximum trim angle for shallow water operation by keeping the engine
RPM below 2000. If the RPM increases over 2000, if the propeller is deep enough, propeller thrust will cause the trim system to
return the outboard to the 20 degree maximum trim position.

However: Further reading reveals a different indication made later, on Page# 2B-13:

When the engine is running above 2000 RPM,
trim angle is limited to 20 degrees by the trim angle sensor and the PCM.

This last statement IS CORRECT.

Unlike previous Optimax and 2-stroke models, there is NO RELIEF VALVE in the Port-Side Trim Ram. It was that relief valve that performed the "hydraulic limit" feature on previous (legacy) V6 2-Stroke, 3-Ram systems.

The 4-Stroke CMS Trim System relies specifically on inputs from the Trim Position Sensor, combined with the TRIM LIMIT set in the engine's PCM to determine the maximum permitted position. If that position is exceeded, the PCM will limit engine RPM's.

While the manual "seems" to provide conflicting info, reading it at written face value (without assumption that it's "the same as other systems" seems to clear much of this up). And yes: I learned something new today as well!

Final Note: The hydraulic relief measures for trail-out and or contact with an underwater object are still in place. These are separately relieved via the center TILT cylinder's relief valves.