Testing motor on the trailer at ramp

breausaw

Okay so I'm going to go test my motor out at the ramp without launching. I've never done this before so I guess my question is do I leave the straps on or take the straps off and just leave it attached at tthe bow.
I'm thinking of leaving the stern straps on to stabilize the boat because I'm going to put it in gear and run the motor up.
I'm heading there now.

Thanks

thataway · Posted: Thu Jun 23, 2016 12:39 pm Post subject:

Leave the stern straps attached, Only put the boat in far enough to bring water up to the "cavitation" plate on the lower unit. If you take the stern strap off, the stern may float and become uncentered on the trailer, Also when you put the motor in gear, it will push the boat forward on the trailer.

Be careful at the ramp--do not run the motor up too much--can cause damage at the end and side of the ramp.

tsturm

Hunkydory · Posted: Thu Jun 23, 2016 12:50 pm Post subject:

It's been no problem with straps left on for us. We do this routinely when leaving salt water, where the wash outs are busy or not available. On the remote ramps we have used, the boat didn't need to be very deep to have the motors immersed enough to be ran safely.

breausaw · Posted: Thu Jun 23, 2016 2:17 pm Post subject:

Left the straps on had no problem just had to keep pulling the truck forward every once in awhile because the tide was coming in; 40 foot tide today do the math.
Motor still has a problem found a certified verado tech taking the boat there Saturday, overheating problem describe in another thread.

breausaw · Posted: Thu Jun 23, 2016 2:34 pm Post subject:

Foggy

breausaw

Foggy · Posted: Fri Jun 24, 2016 7:34 am Post subject:

Larry H · Posted: Fri Jun 24, 2016 4:20 pm Post subject:

Here's my opinion as a retired OB mechanic.

Running in gear at high rpm's on the trailer (backed down a ramp) is not a good test of the cooling system, and not the best idea. Outboard motors are designed to produce high power and cool properly on a MOVING boat. The water flow from the hull onto and around the motor is important. A stationary motor is trying to suck the water from under the hull and trailer (where the water is shallow) to feed the prop and cooling intake. Without the moving boat feeding water to the prop, the prop is sucking water from the sides ahead of the motor. This can suck air down the hull from the chines and draw air into the water pump intake. The trailer bunks further screw up the water flow.

In addition, as mentioned, the prop wash can erode the lake bottom beyond the end of the ramp. If flushing salt from the motor, that salt goes into the lake, where it can cause problems for the fresh water ecosystem. In some areas, flushing salt into freshwater lakes is prohibited by law.

Running a motor (at idle speed), on the trailer, backed down the ramp, is a good way to check out the battery and starter, and to see if the water pump is pumping. It's not a good way to test for overheating.

Foggy · Posted: Fri Jun 24, 2016 6:11 pm Post subject:

Kushtaka · Posted: Fri Jun 24, 2016 9:21 pm Post subject:

I agree that this isn't a great way to test your motor but for another reason besides it not cooling well. Your prop boat is more akin to a car with a transmission and more importantly a torque converter that allows your engine to unload into the prop as the boat itself gains speed through the water (the torque converter being prop slip). Thus the boat is operating properly with the prop "gripping" smooth water and moving the boat, and can't really be done without the boat moving. That is why you have consistent speed through the water at certain rpms, just like a car does in any given gear.

Thus, on the trailer, your engine has no resistance on it and will gain rpm more quickly and will easily over rev.

Contrast this to a jet boat where rpm = only water volume, and the engine being able to unload normally on a boat at rest. The water being pumped is independent of speed.

As another caution, if your straps extend at an angle backwards from your trailer to their attachment point on your stern they will not keep your boat from moving forward if your bow slips off to one side or another. I've seen it happen. Ugly. Only went a foot or so, but it banged up the front of the boat nicely.