tedburg

I have an old Atlas Van Line 40 size hydro that I built back in 1980 during the time ash from Mount St Helens was falling out of the sky. It has an OPS 40 with a tuned pipe.
I was never able to get the engine to run correctly. I'm sure after all the reading I have done on the forums that I had it much too lean before launching and it was
starved for fuel when under load. I was also running 10% nitro fuel and I am not sure if this is even close to being correct for this vintage OPS 40. What percentage fuel
should I use for this engine and where should I set my pipe lenth. Also how rich should the engine be running out of the water before launch. I am experienced with aircraft
model engines, but don't know how many clicks or turns rich a marine engine should be before launch. The boat was well stored and engine loaded with oil.
Thank for any advice you can give
Ted

ken webb

I have and OPS 40 from the same era. OPS gives no needle valve settings in their owners manual. The only fuel they reference is 75/25 methanol and castor oil. Pipe length is listed at 33cm from glowplug centerline to end of pipie. We use to use 40% nitro back in the day. Hope this helps a little.

jetpack

My Feedback: (1)

Here's some OPS reference I've collected that could help. Click for full size and then save them to your desktop. From there you can enlarge them even more to read, I know the one is hard to see.

Start with the engine rich enough to want to die on shore at idle without blipping the throttle to keep it cleared out and go in with the needle from there if necessary. It should almost want to bog out and die, but recovers and revs out when you blip it. A good saying I came across stated a rich boat will return to shore, and a lean one won't.

After you find your needle setting range and its running ok then you can go back and adjust your throttle trim or lengths for a running idle in the water, and brake to kill it.

tedburg

Thanks Ken and Jetpack That gives me a great starting point