porpoising bad
 

I have a 32 black thunder twin 502s at 3k rpms the boat starts porpoising at around t 3800 rpms the boat becomes unstable
and chine walking and it gets real loose like almost out of control. I have pulled the boat out of the water and checked the drives they are all the way down and equal. Manually checked the rams and made sure. Props are the same pitch so I am at a loss as to what would be causing this. Any Ideas as why this boat would porpoise at such a low rpm and what I can do to stop it.

Is this the black and white boat from the Ozarks area? The only other things to check is to see if one of the props hubs is slipping and or see if the drive ratios match. The boat itself should be a great running hull. If this is the black and white boat I would also look at the steering, I can’t remember what was wrong on it but the dealer pointed something out when we were looking at it.

Also check the prop rotation. Turning them in should get a little more speed but can make it a handfull to operate. Turning out is slower but it handles better. In most cases.

not doing anything crazy different with load, filling up fuel more, have boat loaded with more people or junk.

My boat tends to porpoise more when its loaded.

What props are on it?????? Do you have trim tabs?????

This is the boat from around the LOZ I know that the prop hubs aren't slipping because it doesn't rev up when pushing it over on plane and thats when there under there most stress. I believe I am rumming either 23p or 25p mirage ss props and they are both the same pitch. They have to be on the right way other wise the boat would go opposite of the direction that you want to go. Did that once so I am sure they are on the correct drive. I also have the big Kiekefer tabs. I can make the boat stop porpoising if I put some tabs down but when you start to go faster with tabs down the boat starts to get unstable. Alot of side to side motion. With no tabs I havent even put the coals to it yet because it really starts rocking from side to side almost like its about to break loose and come around on me.

Too much trim???

hot java

The drives are all of the way down and when out of the water I made sure that they were down as far as they could be by the distance left on the trim rams

Here are some pictures of the boat and drives. I was looking at that boat but couldn’t justify the price especially without the trailer. Hope you beat the guy up on price. Anyway if you want to know anything more about the boat, talk to
Coolerman
PF Marine

He was the original owner of the boat.


Good luck to you! Please post some pics and progress on the new forum restorations and upgrades.

http://s1136.photobucket.com/albums/...ack%20Thunder/

1987 pachanga
That is the same boat I beat the owner up pretty bad on the price because one of the motors and drives was sick and I already had a trailer so that really wasn't a factor for me. So you know the owner before the last owner? PF marine I cant find them in the phone book is that there full name? or do you have a numer for them. Any help would be appreciated.

PM sent!

not to be gay is this your first boat? Because if it is maybe your idea of is bad what is normal is skewed. Just wondering not putting anybody down. But I would say your props are about right or at least close enough where it shouldnt be the issue.

The only other things I can think of is your rams are going bad, they might not be bad to the point where you can manually push them up and but maybe under load they are giving some.

Anybody could a soft transom cause this potentially?

Also what kind of waves or weather you in because regardless of boat or lenth enough chop and speed its going to do it. Also sometimes in these boats faster is better. At least on my fountain it hates going 30-35 and its sweet spot is more in the 40 zone.

fixx
 

dude??? have you ever drivin a boat before?? not to be a smart azz of trying to cut you doen what so ever...it sounds like you not trimming the drives up after you get the boat on plane and the boat is what they call bow steering and goes in any direction with the waves..espically with those mirage + props which are bow lifting props which is most likely lifting the azz of the boat out of the water and with the trim all the way down is driving the nose too deep and the bow is running too wet..

after you get on plane trim that ***** up until it starts to porpose and bump it down until it stops porposing then hammer it and hang on..get back to us after doing this and let us know if it works for you..if youe really cautious have a friend that knows how to drive a twin engine boat teach you how to drive it...

+1 Mike. If i trim my 255 in"heavy bow"it darts around everywhere...like a top water bass lure.

Seriously...as soon as the bow falls get those drives about a third of the way our and set the tabs neutral...keep the bow out of the water so the boats leading edge is about 25% of the boats length out of the water. Try that and get back.

If that's not it you have some drive/engine placement dynamic issues.

This is not a put down at all...we just don't want you hurting yourself or anyone else.

Guys this isn't my 1st go fast boat. I just got out of it for awhile (kids) I actually had a twin to this boat just a couple yrs older and it was nothing like this. It was stable throughout the entire throttle range even when I was trimming it out hard for more speed. This one is so much more unstable and porpoises so bad that I was really concerned about dropping the hammer on it. Im going to try pushing the drives out and see if it will push past it. Every other boat that I have ever had if it starts porpoising pull the drive in and it will settle down if you want speed you push the drive out to get the bow to come up. Also though the chine walking starts to get really bad around 3800rpm which equals 50mph it really feels loose and I am comparing this to the last black thunder that I had. Any ideas why the chine walking at such low rpms. And by chine walking I mean alot of side to side motion.

the boat i just bought had the exact same symptoms.

it was air inthe steering system and it was lettign the drives moves around at will. was very dangerous. my bet is that somehow theres play in the steering.

check it out.

2ton
That would make sense even a small amount of back and forth would would act like chine walk at low rpm . I will check this weekend and see if anything is loose. Thanks

Sounds like your gimbals are worn out causing the drives to move side to side on their own

i had a friend that put a solas 4 blade on his boat and it would porpose so bad it felt like the boat was literly jumping 6-10' waves,,i put a 3 blade back on it and the problem went away..

I agree with the thoughts that either theres an issue with the steering or the gimbles. I doubt that chine walk is the issue at those speeds. Thats quite a heavy boat and not going fast enough to get loose in the rear. As for the porposing. I second the bow steering caused by the full trim in. I get a porpose sometimes around 100mph depending on water conditions and load on the boat. Hang on, trim it out and see if you can push through it. Your props aren't carrying the bow, either because of the over trim in or their just not the right props. Are you spinning in or out? Try switching them, I go with in on V's and out on cats but that a pretty narrow ass so out might work better for you till you get your sea feelings back. Just my 2ct's worth.

when pacahnga22 and i looked at that boat last year i swear they said it had some sort of steering issue. i dont think its the driver of the boat i am thinking that it has a gimble or steering issue going on. that boat is a big mofo, chine walking at 50 seems crazy. go back there and see if the pins are worn out or there is allot of play in the cable. sounds like its time for full hydraulic steering ;)

Thanks alot for all the input everyone I am going to pull boat out this weekend and check everything in the steering system. It could be anything from the rack to the gimbal housing being wore out at the pins possibly.
I checked the gimbal bearings and all was good there but didn't check the pins to make sure they were tight. It might even be the steering ram is loose or letting the drives move just ever so slightly. but at higher rpms it would act like chine walk 1/2"of slop either direction would really translate into alot of movement when you get all that weight shifting back and forth. Any way thanks for the input everyone more will follow next week after I check it this weekend.