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150 EFI WOT question

A

Airchair

Member
Hi guys, I have a question regarding WOT on my 07' 150 EFI. On the makers plate on the engine it says WOT should be 5850 rpm's. My question is where should the trim be to achieve these revs? With my motor trimmed all the way down, I only get around 5200 rmp at full throttle. Is this correct? Is there a general rule where manufacturers get the WOT revs with regards to trim setting? Regards Greg
 
Hi Greg. Your question is a tricky one as the ultimate WOT RPM is dependent on your overall setup. Engine trim is one factor as is engine height on the transom and the pitch and type of prop in use.

In my experience running any rig at full trim down at WOT will not allow the motor to run at it's maximum RPM and if it does you need a prop with more pitch.

On my boat I start out at full trim down and trim up when underway to a point where I feel a burst of additional speed while under maximum control (Too far up can cause the boat to chinewalk and porpoise and in extreme cases loose water pressure to the pump.
 
If your at WOT and full trim an FTB(full tilt boogie) and only turn 5200rpm you need to drop 1 prop size, if at WOT/FTB and over 6000 rpm need to go up a size as running a EFI over 6000rpm makes run on lean side with factory ECU...
 
Hi Keith, thanks for the reply. What gains would you expect to achieve from full down trim to maximum usable trim in the out position? Obviously you don't want to trim out too much due to what you wrote in your previous answer, but lets say from fully trimmed in to half trim? Would you expect to gain 500 revs? regards Greg
 
[QUOTEWhat gains would you expect to achieve from full down trim to maximum usable trim in the out position?][/QUOTE]
Engine RPM will increase and speed will increase as less wetted surface/friction....
but lets say from fully trimmed in to half trim? Would you expect to gain 500 revs?
Click to expand...
Depending on the boat type you should see a rpm increase. If this is a pontoon boat trim till engine is level as this is best attitude unless its a performance tri-toon.
 
Hi Greg. Apologies for the delayed reply. I'll have to look at it the next time out, but I do know although my throttle may be at WOT the motor will not achieve the maximum (ideal) RPM until I trim it up somewhat. At least halfway between fully down and too high. The other 50% of the trim up provides a "burst of speed" as it gains lift on the nose... hope this making some sense.

There is also a difference based on the load and balance in the boat. I generally floor it and then play with the trim until I see it reaching the max rpm's and speed.... Make sure you have a nice open piece of water as a 150 will be doing upwards of 50 MPH with little load at full chat..
 
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