Nice paint job.... Looks like one of m.... well nice paint job... LOL!
Sounds like the engines are too lean. If this is your first time using MAC engines they often sound to rich on the beach which makes one want to lean them down too much.
You may want to run with some lower pitch props. 5.2 to 5.6 1667s or H38s or maybe even stock with no pitch. I am not sure the holes in the cowl matter much. I have run with just one in the middle similar to what I see on yours.
Are those pipes the .90/1" pipes or the .67/.84 pipes. I tried the .67/.84 pipe on an .84 but it doesn't seem to be performing as of yet. It's awesome on a .67 but haven't found the combo for the .84. The Black AB pipes work well though. Just some things to consider.
But before you add to your already expensive investment because all of us who have run twins know that you have, try this. You may want to richen them up so more fuel gets to them. A flow meter is great once you have found your set-up. They help you maintain it in different weather conditions.
It will take trial and error to get it there. But try richening in the needle (you know... open the needle valve up so more fuel flows through). You can do this by starting one engine. Idle it... then give the engine full throttle briefly before the engine revs to high (you don't want to blow those motors that are almost extinct) if the engine revs to high open the valve up a little more. Do it until it is obvious that the engine is not reving anywhere near it's peak then shut that engine down. Start the other engine and repeat until you get the engine acheiving a similar rev as the first. Remember you don't want the engines to rev up much at all. Then start them both together. Adjust the needles so they sound like they are revving up to the same RPM. Remember... you don't want them to revv up much at all. After you have them running the same then launch the boat. The boat should keep running though not near it's top speed. The engines should trot along at a moderate RPM. Listen to see if the engines are running the same speed. If they are not... close up the needle valve slightly on the one that is coldest after you bring it in. Run the boat again and repeat until you get the engine running the same. The boat should be running with no problem.
Once the engines are running the same you can start screwing in the needle valve maybe an 1/8th of turn at a time. You better bring a lot of fuel as this is definitely the slow (yet cautious) road to the solution. Plus you don't want to run your engines to lean anyway from what Andy says it's easy to stick a piston on the twins although I have yet to do that on a MAC... but like I said you don't want to take a chance on destroying an engine especially hard to find/get ones.
Once you have the boat really humming I would suspect you would be running between 85 and 90mph. Once the boat starts singing pretty well then you can Flow it. Then try different props, and pipe lengths. The last twin I ran closest to your set-up was radared in a race one day at 87.
Hope this helps.
Hi many thanks to all riplys on my broblems , after all the riply on my twin 84 Mac SGX
i deed same canges.
1) Cange all fuel lines for beter fuel flow.
2) Re the props i deed cange to 1667 cut to 64 5.5 cup.
3) Cange to Mac Coy NC-9 Glow plugs are colder.
4) I deed order the Flow Meter too.
Hop by nest weekend i will try to make a beter run with the SGX.
Many thanks to all and keep on posting.
