20XD w/300R Setup Help

[RGuthrie]

Barbarian - yes...trying to fix the hole shot blow out. Boat will push the boat out of the water like a rocket but as soon as the bow drops she starts spinning and I have to start patting the gas. I know I'm repeating myself but its like a dragster doing a burn out. If you lucky it will hook up and your gone. Once it hooks up everything else runs normal but haven't aired it out yet, just run her to 85 and back. My first Bullet was a 20XD that had a 280 and prop was a 29 spinelli, it would spin but always hooked up. This thing spins the 32 like I just lost the prop once the bow drops. I also want to add I have added 4 volleyballs in jackplate to compensate for the weight difference recommended by hydrodynamics.

[WVBullet]

I have a 300R 1.60 SM on a 21SDC. I’ve tried a foil, 2” less setback, wedges & a long barrel original bravo1 and none of these things helped the tail digging on holeshot. I caint figure it out. I had a 300XS 1.62 SM with a foil prior & the boat would fly out with very little bow rise & no tail digging.

Wow! You’ve tried quite a bit. What the heck makes this motor so much different from the XS?!? Especially you having a 21SDC, that longer bow only needed stern lift. Between the wedges and foil, that should have given you all the stern lift you needed. Is the power and torque that they claim they have really there in the low end? I don’t get it. I’ve contemplated changing out my 300xs for a 300r. I don’t own one yet, but I’d sure like to know what it’s going to take. I know you can’t have the best of both worlds with a beast holeshot and super topend, but I’d at least like a decent holeshot, then blow them away alittle ways down the lake/river.

[WVBullet]

Barbarian - yes...trying to fix the hole shot blow out. Boat will push the boat out of the water like a rocket but as soon as the bow drops she starts spinning and I have to start patting the gas. I know I'm repeating myself but its like a dragster doing a burn out. If you lucky it will hook up and your gone. Once it hooks up everything else runs normal but haven't aired it out yet, just run her to 85 and back. My first Bullet was a 20XD that had a 280 and prop was a 29 spinelli, it would spin but always hooked up. This thing spins the 32 like I just lost the prop once the bow drops. I also want to add I have added 4 volleyballs in jackplate to compensate for the weight difference recommended by hydrodynamics.

Well that answers one of post#22 questions. So blowout is your only issue? Comes out great and runs great, just blows out on roll over?

[clint21xd]

I have a 21rdc with 300R. Prop I'm running with good results so far is a PowerTech BRV 5 30 pitch. It is a 5 bladed Bravo copy and price is right at $700. So far I've been able to get right at 92 with 2 people, empty live wells and fully loaded. Hole shot isn't bad at all with minimal slip on break over.

[rocketmanjp]

Well that answers one of post#22 questions. So blowout is your only issue? Comes out great and runs great, just blows out on roll over?

I have a hydraulic plate. If I take off with it all the way down, motor @ 1/4" below, there is no blowout on breakover. If I take off with it 1+" above it will spin bad like this and very hard to feather it into biting. 29 Bravo1 with 4 PVS holes with large hole plugs. I just put small hole plugs in it to try next outing to see if that helps any taking off above pad.

[rocketmanjp]

I have a 21rdc with 300R. Prop I'm running with good results so far is a PowerTech BRV 5 30 pitch. It is a 5 bladed Bravo copy and price is right at $700. So far I've been able to get right at 92 with 2 people, empty live wells and fully loaded. Hole shot isn't bad at all with minimal slip on break over.

Didn't you have to get this prop worked on by Croxton to get it to perform like you wanted it to?

[clint21xd]

Didn't you have to get this prop worked on by Croxton to get it to perform like you wanted it to?

This prop is untouched.

[sowenssw]

I have a 20xdc with a 250R flashed to 325hp. When I bought the boat new in 2003 I had a 2.5 280hp on it, then went to a 250 Sport due to fuel availability. Since then added (2) 10' power poles and went to a 36v trolling motor, so I've been from super light to adding a lot of weight. I think there is only about ~12 pounds difference between the 250R and my old 250 Sport. The 280 always had hole shot issues even light, as did the 250 Sport (both had sport masters with 1:62's), I was never impressed with the hole shot on either engine, both ran out good once on plane and I wasn't running a super big prop on either engine either.

I'm in the early stages of setting up, so not sure where I'm going to end up. I only have a worked 27 hydro, with a full flare and long barrel so I naturally started with that, only 3/4" above pad, the hole shot is really good, but only running out in the mid 80's at 6300, (it will for sure turn to the limiter but I know the props too small so no need to push it hard) so I have some work to do. What I have noticed about the v8 4 stroke vs the 280 and the 250 Sport is, if I ease into the throttle really easy to get on plane the boat doesn't dig in, it just lays and rolls over nice and smooth and is on plane, if I hammer it like I used to the 2 stroke's the v8 digs a pretty good hole and has a hard time pulling out, that's just my personal observation though, I'm prob full of crap.

How I stumbled on to this is, during break-in I was messing around with it, and I eased into it and just held it at 1500 rpm and I couldn't believe it but the boat eased over on plane and laid down, it took it a minute but it really amazed me that it even got on plane and I never changed rpm's. So then I hammered it like I've always done and it dug such a hole it took longer for it to dig out. Not saying 1500 rpm is the deal, but maybe there is something to easing in to the v8's vs hammering it to get on plane???

I really think the v8's have a lot of potential, but I think we are going to have to be open minded and throw everything out the window that we learned setting up 2 strokes.

[sowenssw]

RGuthrie, how much space is between the prop and lower unit housing? I have less than 1/8", prob more like 3/32", if it has too much space its going to act just like PVS holes and could cause it to blow out. I know the v8's don't work well with PVS holes, I have all 8 of my PVS holes plugged solid. Just something to look at.

[River Rocket]

Sorry, XB21 Allison guy lurking in the Bullet forum.

It is so interesting how the different boats perform differently. I went 300XS to 300R. With the 1.62 XS I ran 8 open PVS holes on all props. Even the 26p I raced with when light. On the R it is the exact same. On my 300R 1.75 I run 8 open holes. I took my 32 Promax and hand drilled it out myself experimenting starting with 3/16" holes. When graphed out I could watch the holeshot get better as I moved up to 8 PVS holes. I race with my 28 Promax and even with the boat completely cleaned out of all my fishing gear I can't blow out a 28p Promax with 8 open PVS holes. It just pulls like a freight train.

Here is he 28 Promax in action blasting the limiter. As you can see it just digs in and goes. I mash the gas and never take my foot off.

[bamacj]

Comparing the two brands will be an interesting discussion, Ive compared props with Johnny's 2+2 and what worked good on his Allison worked as well on my SS. The props we tried reacted similar on both hulls. The promax put a kink in the plan. My 27pmax worked by Matt in longview TX ran great at 93 very close to the limiter, but hole shot was embarrassing. I could never get that dialed in. Put that 27 pmax on Joe Lee's Allison and it was a beast out the hole. So far I've had 3 pmax props on my Bullet, none have had any kind of holeshot.

[River Rocket]

Agree. It’s just crazy how the props can behave so different on some boats. I think that’s why we are all into this. It’s fun learning what makes them tick.

[alli ss]

If you cant just slap a 28 bravo on there and go run it pretty good something is wrong. Every other motor on the market is this way from a 225promax to a 300x to a 260. Im not saying that would be your end all prop but i havent seen anybody yet happy with their v8 merc without dumping a couple grand in a prop and usually a few of them. Something aint right. Ive been around forever just like AV and agree with him on this for sure.

[RGuthrie]

All holes are plugged and has exhaust seal ring so exhaust is going through the prop, not over it at all. I've raised the motor and it's now at 1 1/4" above pad. Hopefully weather will permit this weekend so I can do a little more testing and I'l post the results once I do. Who knows they may have made a mistake at the factory and put a 300R cowling on 450R... I'll post once I do some more testing and thanks again for all the help.

[sowenssw]

I agree with alli ss, back in the day, didn't matter if you had a 280, 250 Sport or 300x or xs, each had similar starting points and could work from there. The baselines for those engines didn't seem to change much. As I read about more and more v8''s on Bullets and Alli's, its crazy how everything differs from boat to boat, even Bullet to Bullet with the same motors are reacting completely different. Seems to be a lot more variables with the v8's

[falconpilot]

Local dealer having same problem with 21SST and 300R with 1.60’s...he solved all the problems by moving setback in to 4’” total..boat flies out of hole, light or loaded...

[WVBullet]

Local dealer having same problem with 21SST and 300R with 1.60’s...he solved all the problems by moving setback in to 4’” total..boat flies out of hole, light or loaded...

That’s interesting to know, Jim. My thinking with farther setback, based on fulcrum, would actually help better in the lift. Now as far as the OP’s roll over that may actually help.

[sowenssw]

Well....I tried a stock out of the box 28 Bravo last night on my 20XDC with my flashed 250R (325HP), full tank of fuel, live well full, tournament loaded, boat absolutely rips out of the hole, just a slight blow out when it breaks over but never stops pulling, from there it grabs both a$$ cheeks and rockets to 85+ better than my old modified 280 or my previous 250 Sport ever thought about. I can run a bigger pitch prop and gain top speed and give up some hole shot, which I plan to do. I think there is a better prop out there, and I need to come way up with the motor still, but it at least gave me a baseline, and heading in the right direction.

Still have the issue with it getting really loose when I start to slow down, I mean pucker up tight getting loose. Feels like its going into GC blow out. The Bravo is a 15-1/4" diameter prop, I'm thinking its going to take a larger diameter prop to help correct the GC blow out. Brian at Prop City in Oklahoma City is having a couple larger props cast and we are going to experiment.

I think I actually saw a small glimps of the potential of these engines....very impressive

[falconpilot]

I tried a 16" diameter 4 blade Hering on the 21SST and 300R that I had. It did not help..it was just too much diameter to get it out of hole....The flair on the barrel is of Bravo is what is creating the lift and cause your stern to be loose. My go to prop was a 32 Bravo XS that I cut the flair off of...think we took about a 1" on the back of prop..I could run that prop 2" + and it felt solid...It still wasn't great by any means getting out of the hole, but best combo I found for holeshot and top end - it'd run 92-94 with medium load..really hot weather..95 plus the holeshot got worse and top end with two was high 80's..The perfect prop would be a 15" ProMax if Mercury would ever make one..

[sowenssw]

Thank you for the input falconpilot, I'm betting you are spot on with the flare on the barrel causing it to get loose. The stern rides so much higher than what I'm used to I'm guessing because of the flair, so what you are saying makes sense. I'm only 3/4" above pad and I didn't get a chance this weekend to raise the motor any, so hoping to try that this week. I'm going to see if I can find a 30-32 bravo XS with the barrel cut off and try. Did the shorter barrel help your hole shot?