Need Engine Help Quick!!
05-05-2004, 08:40 PM
#14
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Location: Kansas City, Missouri, USA
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Matt still has the boat and he's been more than helpful. That group over there is amazing. We are looking at the MSD box now because it has some technology in it that allows it to retard the timing depnding on the boost. We thought we had bypassed it by locking the timing at 34, but we may not have been totally successful. Does anyone have experience with this type of MSD boxes?
05-06-2004, 06:54 AM
#16
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MSD 6 BTM ? Boost timing master? It will retard timing regardless of what the distributer is doing. I have no first hand experience but the literature says it is adjustable from 0 to 3 degrees of retard for every pound of boost. Sounds like a great idea, set timing at 36 and have the box take out 1 degree for every pound of boost.
05-06-2004, 10:30 PM
#17
Motors are not very smart. 5 pounds of boost is 5 pounds of boost. On a 420 vs a 170 cfm there may be a slightly cooler intake air temp which would help HP.
Your jetting should be in the high 80's with 2 X 850 carbs, which is too much carb for your setup. But it will work, the venturi signal will be less than desirable since one 850 can support over 500 hp. Two are good over 1000hp. Stock 850's usually come with 80 jets, and this is most likely where your horsepower is lost. If its this lean you will kill the motor, especially at 34 degrees timing!
If the timing is locked at 34, this is too much, but Mercury seems to recommend 34. Maybe they can get away with it with a 7.5 CR. I would try 28-30.
John B
Your jetting should be in the high 80's with 2 X 850 carbs, which is too much carb for your setup. But it will work, the venturi signal will be less than desirable since one 850 can support over 500 hp. Two are good over 1000hp. Stock 850's usually come with 80 jets, and this is most likely where your horsepower is lost. If its this lean you will kill the motor, especially at 34 degrees timing!
If the timing is locked at 34, this is too much, but Mercury seems to recommend 34. Maybe they can get away with it with a 7.5 CR. I would try 28-30.
John B
05-06-2004, 10:37 PM
#18
Charter Member # 55
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What are some baseline stats???
What props, what rpm, and what speed did you normally get with the stock 525's???
Then using the same props, what happened????
You need to figure out some prop slip numbers to determine whether you lost HP with the engines or increased prop slip with the nosecones.
If the slip is the same, then the engines are down on power. If the slip is up then its the nosecones.
What props, what rpm, and what speed did you normally get with the stock 525's???
Then using the same props, what happened????
You need to figure out some prop slip numbers to determine whether you lost HP with the engines or increased prop slip with the nosecones.
If the slip is the same, then the engines are down on power. If the slip is up then its the nosecones.
