Considering dyno-testing / procedures for marine engine?
 

I am toying around with spending the money and having my engine put on a dyno at the local shop before dropping it in the boat. The main reason for this is to hopefully hone in on my fuel and timing curves. I don't think he really has provisions for me to run my wet exhaust, since he uses a closed cooling system. Also, I'm not sure how I would run it with the Merc wiring harness and T-Bolt IV ignition system.

Has anyone else run their engines with the Merc ignition on a dyno? Did you just run a hot wire and ground to the appropriate pins on the harness? What about fuel pumps? I'm running an electric pump right now.

Any other things I need to consider?

If you want a baseline of what HP you engine is - do it.

If you arent running wet exhaust you are wasting your time tuning it... You might even be wasting your time tuning it on the dyno no matter what.

Yeah, thought about how the wet exhaust versus dry exhaust might affect carb settings. I am running Lightnings, which should get me more in the ballpark of what the dyno header produces in regards to back pressure. Maybe I need to just build a startup cart and spend the money for the dyno testing on a set of EGT gauges or something.

budman,the dyno will get you in the ballpark,but the best way to tune it in the boat is with a wideband 02 meter,i like the one FAST sells with dual sensors,one for each bank.they dont like any water on the sensor so they dont work with a wet exhaust.

Dyno'ing is nice to see what kind of HP your making, and also a good tool to give you a idea of what kind of ignition lead the engine likes. But, also tuning in the boat is really my first choice like Mike Tkach said. With a AFR meter.

The fuel curve can be quite different in the boat. ON the dyno, with good air, big dry dyno headers, you can tune for say 12.0 if that's your number. But once its in the boat and its 90*, with wet exhaust, flame arrestor, enclosed engine compartment, you may find the AFR's now in the low 11's or even 10's. So the dyno tune is no longer valid. Normally you wont blow it up, because rarely does the engine need more fuel in the boat then the dyno.

The AFR will not only tell you jetting and what not, it will also alert you to fuel supply issues if the fuel system cant keep up....or show that lean spot at part throttle you may not have seen on the dyno pulls.

So what kind of money are you talking about for one of those setups? I suppose the headers would have to have some type of bungs installed through the water jackets where the collector starts to get a reading. Might not be very conducive to my setup, since I will be running collectors that have silent choice built into them.

getting it to run should be nothing more than buying a harness pigtail and wiring it up appropriatly... about 20 bucks from any number of places. i think the dyno idea is a great one and should be SOP for any number of reasons , the tuning aspect not withstanding. you get to break it in and set it up properly the first time. you get to run it long enough to find out if there are any issues or leaks or wierdness and when you are done you get to change the oil and cut up the filter and confirm everything you need to confirm. if someone built the motor for you you get to sort any warrantee issues right off without any question of liability and when you are all said and done you get to put it in the boat and know what to expect when you turn the key and if you DON'T get what you expect, you know its an installation issue as opposed to something else. doing the dyno program is the best money you will ever spend.

On thunderbolt IV ignition all you need is the battery cables hooked and a jumper from + battery to + coil. Electric pump should be running through an oil pressure switch and relay so applying power to + coil will get the pump running also as soon as there is any oil pressure

We dyno tune everything for the reasons given above. Finding the engines potential power and matching twin engine packages is another plus.

Well, the twin engine thing is out the window for me since this is a single, but see where you're coming from. From the sound of things, I probably will have to do most of my tuning on the water anyway, so that normal benefit might not apply. I'm wondering if I might do better just to build myself a startup cart to run the engine before it gets dropped in. That would give me a lot of the benefits of the dyno, and I could use it for future builds. The warranty issue does not apply because I am building this thing myself.

I have one of those roll-around engine cradles available. I'm wondering if I could modify one of those to strengthen and stabilize it, and add a gauge panel and fuel delivery system to it.