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| Allison 13r T750 or T850?? http://hpbc.ca/viewtopic.php?f=18&t=70 |
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| Author: | wildcatt [ April 7th, 2013, 8:03 am ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Looks Sweet Dave!!!!! |
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| Author: | LittleCharger [ April 7th, 2013, 8:56 am ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Awesome Dave Really looks good! |
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| Author: | tunnelv [ April 7th, 2013, 11:57 am ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Looking Really good Dave! |
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| Author: | WalkWithMax [ May 4th, 2013, 8:43 pm ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Well, I got my Geiger Tech steering bars on and went out for a ride in the "weapon of mass T750 distruction". Its kinda like a 56'er that only runs on two cylinders!!  At first, I ran it with the air box off. I was very dissapointed at the speed and it was sputtering at top end. I put the air box back on, gained some speed and the sputtering went away. (I guess those OMC engineers knew what they were doing??) It was a great day for a ride!! ...next stop, T Party! |
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| Author: | Hounddog [ May 5th, 2013, 9:35 am ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Dave, you may need to go up a jet size on that motor. Check with LC to see what jets he was running. Both the 2 cylinder 45 cubic inch and 3 cylinder 56'r like fuel. The OMC 49 generally runs a little better with the stock jet and some a jet size smaller. Also check the carb gaskets. Any air leak there will cause the same problem. Its better to run a bit fat on the jetting initially. IF? you're running larger jets now then that can cause the same problem. If the powerhead is run in, put a small prop on it and see what rpm it will turn before it goes flat. If it is a 100 block with a good crank it should run low 7000's and make power up to the limit. Some 45's go flat sooner. It doesn't mean the powerhead is no good, it means you have to prop the boat different. |
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| Author: | WalkWithMax [ May 5th, 2013, 6:55 pm ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Thanks for your reply Don! The motor is a used, but clean 100 block(not a fresh rebuild) with 145lbs of compression and it has stock jets. Why would the problem go away when I put the airbox back on? I gained 5 mph after putting the air box back on! lol! I checked the plugs and they were a dark tan colour. "My" 56'er ran sweet with the air box on too!? Oh ya, the gear case I got from you 2 years ago works great too! 
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| Author: | idvette [ May 5th, 2013, 7:52 pm ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
By the sounds of things you may be leaning out, carbs can't add enough fuel for the amount of air you're sucking in. The air box offers a bit of a buffer, the motor can only ingest what the air box can allow. Pull that off and you've lost a restriction, now you're limited by the size of your carb Venturi... Find some fatter jets and try them one step at a time. |
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| Author: | jake@elsey.ca [ May 5th, 2013, 11:47 pm ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Definitely leave the air box on. 5mph right?? |
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| Author: | Hounddog [ May 6th, 2013, 8:43 am ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Dave pleased to hear about the gearcase. If the motor is running good, then it may not be too lean. Odd that the air box makes that big a difference. Sounds like you solved the air leak when you added the air box. |
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| Author: | WalkWithMax [ May 6th, 2013, 9:14 am ] |
| Post subject: | Re: Allison 13r T750 or T850?? |
Thanks guys for your responses. The motor runs great and the plugs are a nice brown colour! (I love the colour brown when associated with boats! lol!) I may go up one jet size to be on the safe side though. Thanks, Dave. |
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