Test prop

[alden135]

Good news:<br /><br />I just bought the proper test wheel for my j120tles<br /><br />So....... I need to make a test tank. How big does it have to be to work right? The motor is to big for a trash can I think.<br /><br />I suppose I could back it down the ramp, but I'm always doing this stuff alone.

 

[OBJ]

Re: Test prop

Shoot alden....just back it down the ramp. Then ya' don't have to worry about filling the tank and draining and stuff like that. Test tanks get pretty nasty after a while with carbon and oil stuff.<br /><br />Just leave the boat on the trailer and back it in so the lower unit is covered or to where the engine sets normally when afloat. Doing it from the ramp is a lot better since a lot of times you can't get the engine in the tank just right. Can be a pain. Wish I had a ramp outside my shop.......

 

[alden135]

Re: Test prop

I've never used a test prop before. Do they churn up the water a lot? I only ask because the ramp is pretty muddy at the bottom.

 

[OBJ]

Re: Test prop

Well.....yeah....they will. <br /><br />I run a 9.9 test prop on a 9.9 for the marina owner over on the river.....(he let's me launch for nothin' sometimes so I gotta' keep him happy...... ) and I run it up to WOT to make sure all was cool before I took the rig out. Churned the bottom up pretty good.<br /><br />But also, the farther out you get the rig and keep it higher off the bottom, the less churning you will make. I know some guys that will use there standard prop and just back the boat in and crank it up. Not real sure about that though. I like some load on the prop.

 

[ledgefinder]

Re: Test prop

I run a test prop, on a launching ramp, with 50-115hps. The test prop does churn up the water a bit, and because your boat will still be on the trailer, the prop only a foot or so above the ground. I'd try to find a paved, non-muddy ramp, if possible, or your cooling passages may get silted up.<br /><br />You want to strap the boat down tightly. The test prop is designed to generate as little thrust as possible, so it doesn't push the boat as much as a regular prop, but it still throws water pretty hard. <br /><br />You may be surprised how loud it is, sitting there stationary, at 5500 rpm WOT with the cover off. Those big 'chainsaw engines' really wail. I was testing a 115hp at a deserted backwoods reservior. Ran WOT for a couple minutes to check the cooling, then idled it. Just then a bald eagle hit a fish about 150 ft behind the boat - I don't know if the noise stunned the fish or what!

 

[OBJ]

Re: Test prop

It is amazing how much noise these things make. Usually your in front of the engine running away from the noise with a hood on the engine. Then when your stationary without the hood at WOT....wellllll....it's a tad LOUD!

 

[alden135]

Re: Test prop

ledgefinder, I haven't seen you around the boards much lately.

 

[mikeyzx2]

Re: Test prop

yeah I was over at my wrench's one day when he hooked up a Merc 90 to his dyno. that sucker was wound out, and big difference when standing next to it. LOUD.........I could imagine if it was a six cylinder instead of four.

 

[alden135]

Re: Test prop

Well I'm pretty happy I was able to find one for a reasonable price. At least now I'll be able to test things before I go through all the hassle of launch, drive 20 min in no wake zone to mooring, then out to bay later, only to find out it still isn't right.

 

[R.Johnson]

Re: Test prop

alden: Those tank's not only have to be big, they have to be baffled to work properly. One shop I was at, the tank was probably 6'X 6', and 4' deep. A V-4 makes one hellish blender.