19' Maycraft CC (Porpoising help)

DesolateGreg

Newbie
Jun 22, 2020
19
134
38
whittier
Name
Greg
Boat
16' starcraft
Hi,
I recently purchased a 1999 19' Maycraft CC with a F115 yamaha. Took it out a couple times and it was ok but a little under powered IMO and did do some porpoising it was not as bad if passengers rode near the front of the boat. Was more annoying in smooth water it would porpoise even with the motor trimmed all the way down. In snotty water it actually worked really well just being a little underpowered it would struggle a little to get up on plane if you really had to slow down for something big.
Well a nice F150 yamaha popped up for sale , same year as my 115, low hours and it was too good to pass up so I swapped the 150 on the back. My under powered issue is now gone. The boat jams, gets up on plane and cruises at a much lower RPM now (3600 to 3800). But as you could imagine the porpoising issue has gotten a little worst. I have a few things running through my head on how to fix it:
Adding weight to the nose: There is a 40 gal bait tank behind the drivers helm which would be a nightmare to move up front plus i dont really want it up there. The batteries are under the console. I thought about just throwing some sand bags in the bow but there's probably a better way to fix this lol.
Next would be trim tabs or I have seen some motor mount wedge things. I have zero experience with either. My only issue with trims tabs is the big armar transducer I am going to have to re locate to mount them but I'm willing to figure it out to fix the boat.
Lastly some type of hydrofoil ?
I under stand this is not an exact science but if anyone has insight especially with these hulls specifically I would greatly appreciate it

boat2.jpg


boat.jpg
 
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alex88

Member
May 15, 2006
915
188
41
Oakland
Name
Alex
Boat
2003 Robalo R235
So I have been battling this issue with my 2003 Robalo that was repowered with a heavier 4 stroke. There are a couple things that have caused this.
1. Older outboards had more negative trim than new ones so older transoms have less angle to them. So an old straight transom with newer outboard doesnt trim in as much. So I added transom wedges to correct it, this helped.
2. The further down an outboard is mounted will cause porpoising as well, I had to play with motor height until I found the sweet spot
3. A 4 blade prop will give more stern lift than a foil will.
4. A hydrofoil will also help, Permatrim is the best on the market and the only one I’d use.

Give Ken at PropGods a call, he is flat out amazing at prop issues. Make sure you have engine info, WOT rpm and speed numbers so he can figure out what prop will be best. He will exchange a prop he sells you for a $35 fee and shipping if you aren’t happy, but he has been on the nose for the last two boats I’ve had.
 
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benrd81

Member
May 21, 2009
623
253
Lompoc, ca
Name
Ben
Boat
2660 Sailfish WAC Reellife
Its more than likely a combination of a heavy 4-stroke when the boat was meant for a 2-stroke and the transom angle. I battled this issue with mine (granted its a 26ft with twins) and have finally gotten it down.
Moving weight ahead will be the biggest thing however wedges and motor height will help as well. 4 blade props made a difference. I have yet to put perma trims on the big boat however it made a hell of a difference on the 12' with a 20hp honda.
 
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DesolateGreg

Newbie
Jun 22, 2020
19
134
38
whittier
Name
Greg
Boat
16' starcraft
A foil should help. A 4 blade prop will lift the stern giving you more balance. There’s a million threads on this issue.
So I have been battling this issue with my 2003 Robalo that was repowered with a heavier 4 stroke. There are a couple things that have caused this.
1. Older outboards had more negative trim than new ones so older transoms have less angle to them. So an old straight transom with newer outboard doesnt trim in as much. So I added transom wedges to correct it, this helped.
2. The further down an outboard is mounted will cause porpoising as well, I had to play with motor height until I found the sweet spot
3. A 4 blade prop will give more stern lift than a foil will.
4. A hydrofoil will also help, Permatrim is the best on the market and the only one I’d use.

Give Ken at PropGods a call, he is flat out amazing at prop issues. Make sure you have engine info, WOT rpm and speed numbers so he can figure out what prop will be best. He will exchange a prop he sells you for a $35 fee and shipping if you aren’t happy, but he has been on the nose for the last two boats I’ve had.

Much appreciated !
 
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DesolateGreg

Newbie
Jun 22, 2020
19
134
38
whittier
Name
Greg
Boat
16' starcraft
Its more than likely a combination of a heavy 4-stroke when the boat was meant for a 2-stroke and the transom angle. I battled this issue with mine (granted its a 26ft with twins) and have finally gotten it down.
Moving weight ahead will be the biggest thing however wedges and motor height will help as well. 4 blade props made a difference. I have yet to put perma trims on the big boat however it made a hell of a difference on the 12' with a 20hp honda.

THANK YOU SIR
 
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Danthefishman

Member
Oct 30, 2006
752
414
La Mesa
Name
Dan
Boat
Aquasport 215DC
I just had this conversation with a buddy who refuses to put a hydrofoil on his boat. I have out them on numerous boats over the years that were either underpowered or porpoised and they have always made a big positive difference. I agree that permatrim if the best one made as well. Trim tabs would be best, but more expensive and more work. If you love the boat and plan on keeping it a long time I'd go with trim tabs. If you're like me and want to improve it but may upgrade every couple years I'd put a permatrim on it.
 
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