View Full Version : Outboard rigging question

10-25-2005, 03:45 AM
I've noticed on my new ride it seems a bit butt heavy. It also tends to porpoise quit a lot. If I trim up the motor at all it's pretty much unbearable. So I started looking and noticed that someone had set the motor up one hole (about 1 1/2") above the lowest setting on the off shore mount. The marks are there where it was mounted lower at some time. Would this cause the problem? Wouldn't lowering the motor also help it to plane faster?
Also, when looking at the lower "fin" on the motor wouldn't it need to be at or below the flat bottom of the boat? It has a flat spot on the last couple of feet of the hull..I think they call this a delta pad, thats the part I'm refering to.
If anyone wants to offer any advise or input before I go and hoist/move a 580 lb. motor, I'd be grateful.

10-25-2005, 05:26 AM
You don't mention what type of boat you have. Is it an Alumaweld? When the motor is fully trimmed, a vertical or past vertical position would give you better out of the hole power and yes, plane faster. The delta pad as you refer to it, is usually more important on a jet drive boat to smooth out the turbulence as it passes the turbine.

10-25-2005, 06:11 AM
I had a bass boat that porpoised at high speeds when I trimmed the motor up for maximum speed. Am not sure if you have the same exact problem. The simplest solution for me was to forego some speed and not trim the motor up quite as high. Choice of correct prop affects porpoising as well. Props that better support a lifted bow diminish porpoising and make the boat more driveable. On my boat that meant using a 4 blade prop rather then a 3 blade. Adding a fin to your cavitation plate(like a Doel-fin) often completely eliminates porpoising and improves holeshot. These are all solutions I've experienced.

High speed porpoising can be dangerous. The boat is unstable. The ideas I mentioned might work for you. I would recommend that you talk to some experts. If it was me, I'd call Phil's Propellor in Redding and desccribe the problem. They have a lot of experience dealing with these types of problems and are usually willing to give free, expert advice. Good Luck.. Larry

10-25-2005, 09:21 AM
You have a North River, right? You need trim tabs. I think that Vance would have to agree. They have very nice riding hulls but they do tend to porpoise. Tabs will solve your problem. You can't quite fix the problem by trimming the engine alone.

As far as your motor height goes, the bottom of the cavitation plate should be about level with lowest point of the transom on most modified V hulls. But as long as your prop is not ventilating, you should be OK.

10-25-2005, 03:01 PM
Talked to Vance today, He suggested a smaller prop to utilize the hp. like fish4fun mentioned. I do have trim tabs however, upon doing some research today, I don't think that they are installed properly. When pushed all the way down they are basically straight out from the hull. I believe this should be the postition when fully retracted thereby pushing down below hull level when activated. Does that sound right? If so, I'll have to move the mounting postition of the piston to a lower place on the transom. RATS!!! holes in the transom now :-/.
Yes Doc, it is a NR, 21' with off shore bracket and 200 Yamaha. If I can get the porpoising problem solved, it will be fantastic.
Oh, and its not from over trimming, it does it even with the motor trimmed full down. With only a small amount of trim up (about 1/4 on the gage) it starts getting out of control. Not a nice feeling! :o

10-25-2005, 03:09 PM
When pushed all the way down they are basically straight out from the hull. I believe this should be the position when fully retracted thereby pushing down below hull level when activated. Does that sound right?

I think that's your problem. Mickey's 20 ft will porpoise unless he uses the trim tabs. They should be able to extend down past the bottom of the transom when fully deployed.

10-25-2005, 03:21 PM
Actually mine will porpoise when trimming the motor for max' speed, I just don't trim the motor so much and it cuts down a couple of MPH but whats the difference when your doing 45 or 43? OK, I know it's 2 MPH ;D If I use my trim tabs to stop the porpoising it feels like I put on a break or something, so I trim the motor all the way for max speed and take it down a little for the better ride, trim tabs work great when you have 3 guys on the boat and it doesn't want to ride straight, down a little on the light side and it rides level ;)

10-25-2005, 06:45 PM
Hey Doc and Mickey,
Thanks for the input.
I took a look at the setup. I can turn the tab bracket, the triangular one that is actually mounted on the tab, 180 degrees and it will effectivly lengthen the rod so that the geometry is very close to the correct position. The only down fall is that instead of pushing the tab at the end, it's pushing it at about 2" from the end. Those tabs look plenty strong so it should be o.k. With that position, the tab is just slightly upward from the hull at full retraction. Should give about 15 degree (estimated) at full throw. I just have to drill two extra holes in the mounting tab to reattatch the now reversed mounting bracket. I like that a LOT better than having to move the arm down the transom and have a bunch of holes to patch below the water line! :'( I'll have to get that all done and take it for a test ride this weekend.

10-25-2005, 08:52 PM
Did you get a warrantee with that boat? You problem seems like something a dealer should be fixing. Kind of make you wonder why the original owner got rid of the boat. Boats should not porpoise. It's dangerous and I would consider the condition to be a safety related defect.

Vance Staplin
10-26-2005, 04:46 AM
Hi Guy's,

I stumbled onto this post this morning. I did speak with Trout Chaser about this issue. I'm positive this is just an elevation/prop issue. This is an older model used boat that did not have factory installed trim tabs. Someone installed those trim tabs after the boat was originally purchased.

Trout Chaser came across this problem up at Pyamid lake last weekend. I'm certain that a prop set up for elevation will eliminate his problem.


10-26-2005, 05:23 AM
He can still re-install his trim tabs so they will be functional ;) Just make sure you seal the holes really good, they are below the water line.

10-27-2005, 05:21 AM
Apparently in '04 the trim tabs were not standard equipment, so we don't know who installed them for sure. I have bought a 17p prop. (was buying it anyway for altitude/backup prop) I will try and run that. If it help a lot, I'll probably try the 4 blade model in 17 or 18 as suggested by Vance and fish4fun.
Also I'm sure the trim tabs will work much better when they are actually running in the water! ::)

Thanks every one for all the help. Hopefully I'll get to try these changes out this weekend. Maybe run it up to Donner for a test run. Of course, I'll have to test out the trolling motor for a few hours too!!! ;D

10-27-2005, 05:48 AM
Hope it all works out. A few of us are going out to Folsom tomorrow. You might try chasing some kings and the drive isn't quite as long. But then Donner's prettier.

10-27-2005, 05:16 PM
Sent you a PM.

11-30-2005, 11:59 AM
I've had a couple of friends with heavy motors and kickers mounted on off-shore platforms experiencing the same problem. It almost seems like the offshore platform/bracket with an outboard on it throws the balance of the boat out of wack with a cantalever ??? 'leveraging' effect making it stern heavy. If you think about it, there is no hull under the bracket/platform to support the weight of the motor. I believe they sorta remedied it with trim tabs, lowering the motors, and redistributing weight (ie, batteries, gear, anchors, passengers) towards the bow.