Building a test tank?

How big and what shape do i need to build a test tank to avoid the prop throwing all the water out? i want to be able to thoroughly test my engine and link and sync it while in the driveway. I was thinking 3 feet long, 1 foot wide and 1 to 2 foot deep, with a lid cut around the leg to try and keep the water in. sound about right? or does it have to be a lot bigger to replicate the true load? its for a mercury 70hp by the way.
thanks, peter

Re: Building a test tank?

Nautique93 said:

How big and what shape do i need to build a test tank to avoid the prop throwing all the water out? i want to be able to thoroughly test my engine and link and sync it while in the driveway. I was thinking 3 feet long, 1 foot wide and 1 to 2 foot deep, with a lid cut around the leg to try and keep the water in. sound about right? or does it have to be a lot bigger to replicate the true load? its for a mercury 70hp by the way.
thanks, peter

Click to expand...

The problem with a test tank is that all of the water in the tank becomes turbulent (full of air) and you won't be pumping water through your engine. You will overheat and damage your motor very quickly. The test tank you describe (6 cubic feet of water) might work for a small outboard, but it won't work for yours. If you want to run the motor while testing it in water, back your boat into the lake and leave it on the trailer. Just make sure your prop is clear and that your boat won't shift on the trailer while running.

Re: Building a test tank?

To simulate operating conditions for that 70 you will need about 1,000 gallons.

I used a 1Kgallon stock watering tank when I had several engines to test, but that water is of no use for anything else after a 2 stroke has puked in it for a while.

Really makes you a tree hugger to see what it can do.

Re: Building a test tank?

Could you run it on a hose while it is in the tank to make sure that it is getting enough water to cool it, and just use the water in the tank for resistance?

Re: Building a test tank?

SBTOM said:

Could you run it on a hose while it is in the tank to make sure that it is getting enough water to cool it, and just use the water in the tank for resistance?

Click to expand...

I tried that and still had problems with throwing water out of the tank and not being able to replenish it fast enough. As the water throws out, the prop has less resistance and will consequently speed up prop and engine rpms and it's almost impossible to get it back to normal without taking the engine out of gear. head to the ramp with your toolbox and save yourself a lot of grief.

Re: Building a test tank?

Yes, you can build a test tank or not.. Just go down to the local farm supply and get a pasture trough. I've got a 4'x2'x'2 one and I throw a piece of plywood and a brick over the back. Alternatively, Home Depot has large plastic bins that you can use but you have to reinforce the sides or they will split. A 2x4 on each side will do the trick.

YOU STILL NEED TO RUN THE MUFFS FOR WATER.

Sorry didn't mean to yell, just want to make sure you got that part. All the tank is for is to let you load the engine for short periods of time. FYI it will make your neighbors happy too. The noise of your repeated tune up attempts will be substantially decreased as well as the amount of smoke.

Re: Building a test tank?

I agree, you could build a tank, but I think its far better, and wiser to back the boat into a lake. As JB said that water, will become VERY poluted in a short time. Not something that should be dumped down the drain, or on a lawn.

Re: Building a test tank?

O.K. now you got me rolling. Wouldn't want to put it down the drain or on the lawn but it's fine to dump it in a resevoir, natural lake, watershed or the ocean.

We all need to take responsibility for the environment but I think your concern is a little absurd. FYI, take a little two cycle oil and pour it on you driveway. It'll evaporate in a day or two. I dump my tank water on my lawn and water my shrubs with it. Doesn't seem to affect them adversley at all but it does positively affect water waste.

As for letting it go down the drain, well your right. I also think we should put rain covers over all of our roadways so the rain doesn't wash all the road oil down the storm drains.. .NOT.

Nope, sorry, just can't find a way to agree with you on your statement.

Re: Building a test tank?

Leave the boat strapped to the trailer and do your testing at a launch ramp when its not too busy during the week. A lot less hassle, who wants a big tank of water in the yard?

Breeding mosquitoes?:redface:

Re: Building a test tank?

Thanks for the replies, i have considered doing it at the lake but it is an hour away, and trying to arrange my mechanic friend to be there at the same time is awkward. I will also be less rushed in the driveway and if i have to change parts, i dont have to tow it another 2 hours to test it again.
Reason for wanting to test it is i recently fitted a new stator which cured the high speed issues, worked for a couple of trips, but now it seems to have limitted power- only just gets on the plane, and the idle has also dropped enough that it stalls when going into gear without reving it first. I want to check i havent messed up the timing when i took the fly wheel off, but if it ran for a few hours fine i dont see how the timing could have changed suddenly. It will also be easier for me to eliminate the fuel system with out hanging off the back of the boat or wading about in the water.
So it sounds like as long as i run the engine on muffs, it wont overheat and the tank water should be able to create at least 50% of the load which will let me go through the fuel system at least, if it has enough load to stop the motor over revving i should be able to link and sync it. I will be starting another post regarding this as my manual isnt too clear.

Re: Building a test tank?

sschefer

Sorry to get you "rolling", I simply stated my oppinion on the test tank. However the point is valid. If you want to cart 1000 gallons of water, to disperse in a lake, fine . Most ppl wouldn't

Re: Building a test tank?

Fuzzytbay said:

sschefer

Sorry to get you "rolling", I simply stated my oppinion on the test tank. However the point is valid. If you want to cart 1000 gallons of water, to disperse in a lake, fine . Most ppl wouldn't

Click to expand...

LOL... I was rolling with laughter.. and 1,000 gals would be quite a bit to haul and a pretty darn big test tank considering the size of a 55 gal drum. The test tank would only hold about 35 gals of water. Plenty to do the job.

Re: Building a test tank?

I have often thought of buying a generator from Northern Tool and making an adapter from the prop shaft to the generator. Then make a load bank of light bulbs or resistance heaters to load the generator down. It would take quite a load for a 70 HP engine, though. You could just about power your entire house with something like that! Especially if you had a big 5 ton heat pump/air conditioner.