Reply With Quotewell, considering we don't need the extra inertia of the flywheel for anything in a jetboat, the added weight and cost would probably be reasons enough not ro run a flywheel.
Just get a good SFI approved flexplate and you'll be fine.
Chris
it's been awhile since I've seen anything about the pro's and cons of each.
The reason I bring it up is I went out to fire up the engine and the starter kept disengaging. After a little investigation, I noticed the flex plate is warped. As soon as the starter rotates the flex plate to the warped side, it disengages.
is one better than the other?
well, considering we don't need the extra inertia of the flywheel for anything in a jetboat, the added weight and cost would probably be reasons enough not ro run a flywheel.
Just get a good SFI approved flexplate and you'll be fine.
Chris
straighten the flex plate. It's not hard.
Steve - What FlexPlate are you running?
Bear,
Although I can't remember the manufacturer, the flex plate I have is SFI approved. When I did the rebuild last year I purchased it from the machime shop.
At least I was told it was SFI approved.
The reason I asked was that we ran a FlexPlate up until the NJBA Summer Break of this passed year ... Then changed to an AL FlyWheel ... Added weight ... About 6 +/- Oz., no big deal since it's rotational mass ... Loss of maybe a fraction of a HP.
The reason we changed was we kept popping the Allan Head Bolts that held the Steel Starter Ring to the AL FlexPlate ... The manufacturer was kind enough to reinstall the Ring three times with no charge before we decided to go the FlyWheel route ... The manufacturer maintained that we had the starter misaligned, but, we Know that was Not The Case, so we changed over to the AL FlyWheel.
What we determined was happening was that the Allan Heads that held the Ring to the Al FlexPlate were spot welded to the heat treated Steel Starter Ring after being installed ... The spot welds crystalized and weakened the Allan Heads resulting in their popping off over a period of time ... Realize that the FlexPlate we were using was SFI Approved and has been used in Funny Cars ... The only difference is that in a Funny Car there is an Inertial Ring and Tq Converter where on a Jet Boat Installation, there is only the FlexPlate held on to the crank by a small mounting ring. What this allows (w/out an inertial ring to stabilize the plate) is the FlexPlate to FLEX like a drum head and work against the weakened Allan Heads ... This combined with the High Compression 'Ms. MoneyPenny' has led to the Allan Head Failures.
As a result of the above, I would recommend that FlexPlates Not Be Used On Jet Boat Motors ... Use an AL FlyWheel ... While the cost for a top end AL FlyWheel is on the order of about $125 more than a SFI FlexPlate, I believe it is well worth it given the damage and injuries that can result from a starter ring "Flying Off". Of course, one must make sure that the starter pinion is properly aligned and its clearance with respect to the starter ring is right.
Just conveying our experience with A FlexPlate on our Jet Boat. Note that while the FlexPlate we were using was a SFI Approved Plate, the particular case of its use in an 'UnBound State' on a High Compression Jet Boat was probably not taken into consideration ... I may be wrong, but, I think the SFI Approval only has to do with the RPMs that they can be Safely Spun At?
http://cgi.ebay.com/ebaymotors/ws/eB...category=33732
I asked Jack about this in the past. He said, early on, they used heavy flywheels way back in the racing days cause when the pump would unload (while racing) the engine would not spin up quite as fast. No rev limiters back then. He also says you tend to be a better reader of the water w/ experience. :boxed:
I use a steel flywheel, like someone would tool up aluminum for an olds, and dont notice any dif from previous boats with flexplate. It still revs easily , no heavy torque converter, and no flex or starting problems. In a continous high RPM use it may also help with crank harmonics like using a larger harmonic balancer.
We're running a Billet AL Flywheel, not a cast.
I run a reactor products (http://reactorproducts.com) flexplate, nice peice that can be had with or without SFI.
Not cheap, but it works.
Talk to Olan.
Brian
Posting Permissions