Update - Might have to get a jack plate for set back

[OBT]

First post is here - http://www.bbcboards.net/showthread.php?t=926455

I need a diagnosis.

I'm still waiting for a 20 pitch stainless steel prop, and still considering the 4" manual jack plate (All I have room for in the garage) as a plan "B" if the new prop doesn't change things.

What I did do since I'm not doing much else while waiting, was to make a few more test runs, and make a video of it, this time with transducers folder up in case, as some one suggested, they were "messing up the water" ahead of the gear case. Turns out there was no difference.

It's 1:43 second long and shows the take off, the engine slip and kick out at around :32 sec as it climbs in speed (My old engine combo did this too) and then a couple of attempts to keep it trimmed at full rpm and speed. You'll see it begin to shake and lose its 'grip" (?) on the water and then me trimming it down a little to smooth it out. Doing that of course reduces speed and rpm. Again, my old engine combo did this too but not nearly as pronounced and with out th lose of speed or rpm. (That I ever noticed)

The only other thing I think I might try is removing some weight up front. I may just have to much tackle up there and perhaps that's setting things out of balance?

Please watch the video and let me know what you think. Thanks.

Two places to watch it... here https://www.facebook.com/mike.jacobs...2256448520506/ and here...

[Rip Bass]

That engine shaking is definitely prop cavitation. Hole shot didn’t look too bad though. What is the prop to pad height now? I looked through the old post and didn’t see it. On the old post,Mdtrtn21 suggested a Tempest prop but I don’t think they are made with a small hub to fit your engine but a Trophy should fit. Trophy has four blades and should have enough bite to lift the bow better than that Laser,if it comes to that. I would try a jack plate first because whatever prop you end up with you’ll still run better with a plate. It’d be nice if there was a dealer around there that would let you try different props.

[OBT]

That engine shaking is definitely prop cavitation. Hole shot didn’t look too bad though. What is the prop to pad height now? I looked through the old post and didn’t see it. On the old post,Mdtrtn21 suggested a Tempest prop but I don’t think they are made with a small hub to fit your engine but a Trophy should fit. Trophy has four blades and should have enough bite to lift the bow better than that Laser,if it comes to that. I would try a jack plate first because whatever prop you end up with you’ll still run better with a plate. It’d be nice if there was a dealer around there that would let you try different props.

4 3/4 in. below pad. Good suggestion with the Trophy though we're trying to get the rpms up closer to the high range, 6300, 4 blades might make that harder. Right now, I have a 20" Pitch coming in and I'm very close to biting the bullet and putting a jack plate on. A 4 in. because of the length of my garage. I have 10 1/2" clearance right now, so maybe I could go with a 5", but I'm not even sure if that's how it works! Does a four inch Jackplate only add another 4 inches to the over all length and a 5", 5 inches? If not I might be in trouble! I wish somebody could answer this one for me! I sure would sleep better tonight!

[alanhore]

If you get a 4" plate it should only add 4" to your total length.

[OBT]

Thanks, I know it was a stupid question, but I had to ask! It was asked along the lines of a "2X4" isn't really 2 by 4! And boy would I feel stupid if after all this is done, that I couldn't close the garage door!

[magfluker]

If you are heavy on tackle up front it will help moving some to the rear, balance is key. Soft plastics, jigs, weights are all in the back for me. It will help some. It will also put emphasis on having to raise the motor as well.

The higher the motor, the better the holeshot too.

[OBT]

Update. Looks like the problems are solved. (And adding a Jack Plate may not be an issue any more)

Made several runs today with the new 20" pitch Laser II pro and I think I've finally reached the top performance I'm going to get and I'm very happy with it!

Here it is:

A very Light chop on the water
1/2 tank of fuel.
"All" my normal 'too much" gear,
New 20" Pitch Laser II Stainless Steel prop, no jack plate
Engine mounted in 2nd hole now, down from third hole
WOT, Full up trim, RPM's 6350-6370, right in the top range that I wanted and a top speed of 51.6 mph.

The fastest that boat has gone since the first day I ran it, and at that time it was totally stripped of gear.

The Hole shot was down to 4 seconds,another improvement.

The WOT "stance" of the boat, in other words, bow lifted and boat fully running on pad felt "perfect"! Its a whole different boat and that engine is a freaking dream. Especially running at the top of it's rpm range.

If the rest of Mercury's FX four strokes run like this one, than they can consider it a Home Run. Its been a hectic couple of weeks playing around with the set-up, but I now declare it... dialed in. Thanks to everyone who helped me out!

[Buccaneer]

But, if you had a jack plate imagine what you could do. Endless possibilities.