260hp I/o expectations

reelapeelin said:
Spare...do they make the electronic (Petronix?) ignition for this motor...that might help him out some here...
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Reel yes they do I converted mine over this year to the pertronics distributor and haven't had a problem since.
My old one fried and when I checked into it there was only 52 of the electronic ignition systems left in the world so that is why I converted mine over.
 
Well I think I have it dialed in better now. I found that part of the old pointer was broken so I was using the wrong notch as a reference it looked to be a aftermarket deal. I used some msd timing tape and centered it to tdc. Runs like a champ now still getting right at 40mph which is fine. Thanks everything guys its much appreciated. What is this patronix conversion? I know about their points conversion thing but these already are breakerless ign correct? Are you doing away with the thunderbolt module all together? Is there any issues with the thunderbolt IV? Anything else I should look at doing as far as reliability is concerned?
 
1224bret said:
Well I think I have it dialed in better now. I found that part of the old pointer was broken so I was using the wrong notch as a reference it looked to be a aftermarket deal. I used some msd timing tape and centered it to tdc. Runs like a champ now still getting right at 40mph which is fine. Thanks everything guys its much appreciated. What is this patronix conversion? I know about their points conversion thing but these already are breakerless ign correct? Are you doing away with the thunderbolt module all together? Is there any issues with the thunderbolt IV? Anything else I should look at doing as far as reliability is concerned?
Click to expand...

Mine was very simple; pull the old distributor and drop in the new one and connect the wires.
 
So you keep the thunderbolt module with the new dizzy? Is the patronix unit a marine unit? Or is it just a self contained 1 wire distributor style?
 
Pertronix isn't going to be any better than the Thunderbolt, a pertronix is great if you are replacing points, but its not needed for the Thunderbolt . If something goes wrong with teh Thunderbolt, a pertronix distributor may be a cheaper alternative, but I prefer the Thunderbolt as it has an electronic curve, rather than mechanical. Keep the set up you have, check your total timing to make sure its coming all teh way in. The V6 boxes are the hot tip on v8s as the timing comes in faster, but I doubt you would be able to tell a differnce
 
Ok one last question regarding the performance of my v. I just ran the numbers on my prop and it is a Michigan wheel aluminium 17p. I'm getting 40mph at 43-4400 rpm doe that sound right? I know when I first made this post a few of you guys said it should be turning a 19-21 pitch. If I want to go stainless I know they normally recommend dropping a few inches off the pitch which would put me at a 15? Sounds awful short on prop for a 260hp inboard to me but I'm not used to the weight of these boats. What are you guys with the v8's running as far as pitch?
 
are you running ALL fresh gas yet?
have you done a compression test?
you only drop pitch when going from 3 blade to 4... from al to ss you will likely stay the same

You want to sort out any and all engine issues before messing w props

Also are you trimming up for max speed?


My 28'er has old school 14.5x17" al props on twin 260's and runs 48 mph
 
Well just as an update I finally had some time to get some work done on the boat. Put fresh fuel in, the 17p aluminum was pretty beat up so I installed a 19p mirage, I'm now getting 41-42mph at 4200 rpm which was with 4 people and a dog in the boat no issue getting on plane. I'm pretty happy with the performance of the boat now I'm right on par with garagenc's numbers. Boat cruises great at around 30mph. So much smoother now with the mirage prop. We spent several hours cruising around lake Kissimmee yesterday afternoon and I'm really digging the way these hulls ride and perform!
 
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