More HP and prop blowout
 

So as my huge list of things to do with the boat dwindles down I have an issue that I have yet to address and need some opinions...

Boat is a 97 Nordic heat original 525 sc now has estimated 7?? horsepower

I have always ran a 28p bravo on this boat since I've owned it and all was fine with the world...not a single blowout in turns out of the hole nothing

I have since ran the boat with the same prop same drive same everything except the HP increase and it is blowing out BAD!! I can barely get it on plane and when I do a small touch of the steering wheel and boom it blows out and you have to start over again

I'm wanting to put a -2 lower on it as I have read several great accounts of it fixing the porpoise and picking up speed as these old non stepped heats have a deep X

So I'm left wondering...is my new found blowout problem caused by the increase in power? I have a labbed 30 that I plan on running but I can't figure why all of a sudden its blowing out and will the shorty lower make it worse??

I have 1.50 gears and I'm also considering a 1.36 shorty as I have also read that some with blowout issues had it cured by the gear change...

What is everyone's thoughts on all of this??

Thanks!

I checked all that....new HD coupler when motor went in but checked it anyway and it still looks new(not spun) and the hub is the metal hub with the rubber tips on it...also the HD version I believe and it as well looks new...If you baby the sh!t out of it I can get it on plane and it starts going ok but like I said if I just touch the wheel it wants to blow out....I could take turns at like 40 before the motor build without an issue...now I can't even turn when its on plane...I'm kinda stumped...everything is the same except the motor?? Could increasing the power cause the prop to blowout?? Like putting a blown big block in a pinto with 14" tires? lol

Thanks

One other variable is the weight of the engine...I'm sure I picked up some weight with the giant blower and such but I think that would help this situation specifically with more weight in the a$$end??

No sir...it does have a nosecone always has...no LWP just a nosecone

Yes it is a bravo and out of curiousity I tried that on both sides of the pin with no change...that was my first thought too hahaha

prop blows out while on plane? Is the drive at neutral when this happens?

No its when I come up on plane, while turning, and slightly when I trim it...mostly when trying to get on plane which I come up easy anyway because I have a bravo with power in front of it lol and it still does it

Did you add a drive shower by chance or relocate any existing drive shower?

no sir...same shower just extended it above the cav plate slightly to accommodate a larger max machine top cap on the upper but below the cav plate it is the same

I'd try a different prop as well, because that's quick and easy.

I'm thinking that's what the plan will be and see what happens...that is when all the ice is off the lakes lol

The labbed 30 I have is cupped a little I guess...I bought it used but that may help as well

I do also have a call into brett at bblades to get his take as well

You are late son..........see #11

Oooops, thanks dad..........didnt scan the thread

I had the same problem with a nose coned XR, switching to a SC housing was the cure.

I have added lots of HP many times in my boating life and have never changed the attitude of the boat. getting on plane was always better because of the higher torque.
didn't you ask this same question earlier?
Sounds to me like something external to the hull has changed,
going with a shorter drive will not help getting on plane.
any chance their is water under the floor in the bow?

Nothing in the bow I know that for sure as I replaced a lot of rotten wood so I know its dry lol...idk what the deal is...gonna try the prop when weather allows and go from there I suppose

Brett was able to fix some props for me on my old 35' Lightning. It was VERY difficult to get on plane with Bravo I 34* props. He worked on them and made them ALOT better.

Agree with tinkerer. Something has changed water flow across bottom of boat or around drive.Got to be frustrating

Sounds like one of two issues, either you are way underpropped for your new build, or the -2 is getting out of the water!

He hasn't put the -2 on yet.

idk, as others have stated it should get on plane with the original prop, has to be something else.

You say that you replaced a lot of wood.
Have you put a straight edge on the bottom of the boat.
Sounds like you may now have a hook in the bottom.
when people replace stringers with the boat on a trailer one of the problems they have is keeping the hull straight.

"Nothing in the bow I know that for sure as I replaced a lot of rotten wood"

What did you change when you did the rotted wood. A little bit of weight in the bow makes a huge difference.

OR

If the new power is a lot heavier, may try adding weight to the bow. Sounds ridiculous but maybe you took out too much weight. Throw 2 or 3 batteries in your cuddy.

Unless something is wrong with the prop - adding HP will not change the planing attitude of a boat unless weight has changed drastically.
Even if You changed from stock cast iron exhaust to headers and stock iron heads to aluminum ones I can't see that causing a boat to not get on plane.
If you went with an aftermarket heavy block it wouldn't add enough weight to make the boat stern heavy.
something has changed besides the HP

All the rotten wood was in the floors of the cockpit mainly...stringers were good was just the floor and 2 bulkheads...there was a small piece in the floor of the cabin that I replaced but went back with glassed marine plywood..the block is original just bored..the only weight gain in the rear is the blower and some accessories...now to be fair I was running it without the rear seat which is maybe 100-150 pounds I would guess but I can't imagine that would cause much of an issue?? Have to pull the boat off the trailer to do some trailer work so I will def check the bottom with a straight edge...hoping its just something with the prop but will def do some investigating! thanks guys!!

That's on the list if this 4 blade I have doesn't work...all the heat threads I see talk about the p5x being the prop of choice but those are all stepped hulls...mine is a "straight bottom" so may try one if all else fails..I am nursing an XR so the extra blade is a little scary hahaha

I have the same issue, rebuilt the motor picked up a bunch of horsepower and stock prop breaks out with anything over half throttle. Once on plane I can hammer it. Nothing else has changed I have found changing the prop does help. Just acquired a labbed 30P 4 blade that I will test when the ice melts. Adding cup will help the prop bite on launch.

You probably need a higher pitched prop. If you added 200hp and still have the same prop as b4 it would be like putting donut tires on a 1/4 mile drag car.

Agreed..and I'm planning on having to reprop but just for a shakedown kinda tuning cruise I left the original...and like I said it wouldn't grab for crap lol...I think first plan is to try my labbed 30 with a little extra cup and see if that remedies it

I'd try a set of unmolested 32p bravo 1s. I'd avoid using a 5 blade prop on a bravo drive high hp single engine boat.

I talked to brett yesterday from bblades and he has some ideas on things we can try...he agreed about the 5 blade on a bravo like you just said...gonna try a worked 4 blade first and see where that goes...he also said without actually being there his guess is the couple hundred pound weight difference from the rear seat and hatch being out could easily have caused my blowout issue..he did say too that if we do go with a 5 blade for cruise speed which I'm ultimately going to be after that his 5 speed or if I can find a p5x would be a better choice over a maximus or the like as they bite less and will be easier on my drive....I know I'm on borrowed time with the bravo and my power level obviously so she will get babied hardcore out of the hole and no hard holeshots from mid range etc. Hopefully I can get her to stay together until I can get an imco upper or something else equivalent