A.V plate is 4.5in below hull...help!

[ross patti]

Hi folks,<br /> Got a 14.5ft open aluminium runabout with a 1976 35hp Johnson.I went the long way around fixing a condenser,now it runs sweet.<br /> The motor is a 35RL76 model. Ithink RL stands for really long !!.From the AV plate to the gear lever it is 24 inches.This results in the AV plate being 4.5 inches below the bottom of the hull.<br /> I have been reading some postings arguing the plate should be 1 or 2 inches above the hull.So my 35 is sitting 6 inches from ideal position?.<br /> At WOT,the boat gets to about 22mph.The hull rides well,planes easily and handles the water well.<br /> However,the back of the boat does look like it's bogging down a bit.The spray doesn't seem to deflect cleanly from the transom,it seems to want to regurgitate around the transom ? [hard to explain ]<br /> It pulls out of the hole easily.I tried a set of fins and pulled them straight off after one trip.The nose would not get out of the water.It was like putting a motor on a shipping container !!!!. That's why I unbolted 'em and called them boomerangs !!!<br /> To raise the 35 up 5 inches means some welding work,which I'll happily do {what,not spend more money on the boat??...you people are sick !}<br /> What changes should I expect?<br /> Am I strangling my rig as is ?? <br /> Will I see an improvement if I get the plate to only level with the hull ? <br /> Why are Patty & Selma so much like our wive's sisters ?????<br /> Any help on the above topics would be gratefully accepted.<br /> Thanks in advance.....

 

[Silvertip]

Re: A.V plate is 4.5in below hull...help!

Take another measurement. Check the distance between the AV plate and the top of the transom bracket (where it sits on the transom). For your boat, this should probably be 15 inches (short shaft). I think you have a long shaft engine (20 inch shaft) on a short shaft transom. Raising the engine even a couple of inches would help a little.

 

[JB]

Re: A.V plate is 4.5in below hull...help!

Rather than modify your transom I would convert the engine to short shaft, Rosco.<br /><br />twincityoutboard.com probably has the necessary parts.<br /><br />Good luck.

 

[mjbrueck]

Re: A.V plate is 4.5in below hull...help!

I know what you mean about the water coming off the transom. I have a friend that runs a 20" shaft on a 15" transom. The boat has more of a "peacock" tail than a rooster tail.<br /><br />If you can build up the transom, that would be the way to go. If you don't want to do that, you can buy a fixed jack plate fairly cheap (a search on iboats will give you several choices).<br /><br />Mounted the right height, you should gain several mph.<br /><br />If your boat is flat-bottomed, you should probably plan on even or just above the bottom of the boat. On deeper V's, you can get away with higher mounting. The higher you mount the engine, the faster you can go, but too high and you'll ventilate in turns or when it gets choppy. <br /><br />And lastly, my sister-in-law looks like Patty & Selma combined, but I don't know why.

 

[phatmanmike]

Re: A.V plate is 4.5in below hull...help!

jack plate !<br /><br />this way you dont need to modify motor in any way!

 

[Solittle]

Re: A.V plate is 4.5in below hull...help!

Not a good comparison but I run a 9.9 long shaft on a 13' short shaft transom tinny and have no problems and don't plan to change it.

 

[ross patti]

Re: A.V plate is 4.5in below hull...help!

Thanks for the replies...<br /> I took the measurement to the transom bracket,and it is 22 inches.It's way long !!<br /> Everyone seems to steer around modifying the transom.As soon as someone explains exactly what a jack plate does,I just might fetch me one.Or twr the whole damn set.<br /> From the bottom of my hull to the top of the transom is 18 inches. I imagine this jack plate will raise the motor the 4 odd inches I need.{and let's face it guys,most of us need another 4 odd inches !!!<br /> So ,am I right in thinking that raising the motor 4 or 5 inches will give it another 3 or 4 mph ?...'Cause the faster we go,the cooler we look,and the longer we fish !!!!!<br /> If anything is to be gained by seeing the motor/transom set-up,your all welcome to come to sunny Australia and have a look-see.<br /> Or,I could post a photo on this site.<br /> Thanks for the help,take care

 

[ross patti]

Re: A.V plate is 4.5in below hull...help!

Hold the phone !!!!<br /> I just went to iboats and found the jack plates were pretty much how I imagined them.<br /> I really think that they will work.<br /> Even the "engine elevator "would do the trick.<br /> I might even custom make a compromise version that has the best of both types. <br /> Your thoughts will be gratefully accepted.

 

[KCLOST]

Re: A.V plate is 4.5in below hull...help!

Is this a tiller motor?<br /><br />If so, consider that in adding a jack-plate which will move the motor further back... Go with a short setback plate if that is a factor for you.

 

[ross patti]

Re: A.V plate is 4.5in below hull...help!

No,KCLOST,it is a forward steer/control.<br /> Should I still go for minimum setback ??<br /> What effect does the setback have ?<br /> When the boat is on the plane,how close to the surface can the top of the prop. get,before it cavitates ?<br /> If I get the AV plate to 2" above the low point of the hull,the prop. will be approx.6" below the surface. Should this be deep enough to stop any cavitation ??<br /> Thanks again...

 

[mjbrueck]

Re: A.V plate is 4.5in below hull...help!

The farther the setback, the higher you can raise your motor (The water is coming up past the back of the transom, so a 6" setback might mean you can operate the motor 1" higher than if the motor is mounted on the transom). As far as the point where your prop starts ventilating, that will have to be trial and error on your boat. Your guess of 2" above the bottom of the transom is going to be the general area.<br /><br />Since you're boat is remote, a larger setback shouldn't be a problem. For tiller boats, moving the engine weight too far back can cause balance problems.<br /><br />If speed is the main concern (and money is only a minor one), go with a jackplate with power trim. Trimming the motor out once on plane should buy you a few more mph.

 

[jtexas]

Re: A.V plate is 4.5in below hull...help!

Patty and Selma are so much like our wives' sisters because we are married to Marge.

 

[Nos4r2]

Re: A.V plate is 4.5in below hull...help!

Originally posted by jtexas:<br /> Patty and Selma are so much like our wives' sisters because we are married to Marge.

What, all of us?!

 

[ross patti]

Re: A.V plate is 4.5in below hull...help!

Hey MJ,jtexas and Nos4r2[you heller dude],<br /> Thanks for the tip on setback.After careful consultation with a couple of boating buddies,I think I'll go with a new plate basically mounted straight onto the transom.<br /> If I figure out how to attach a digital snap or two,then everyone can throw in their opinion .<br /> The more,the merrier !!!<br /> <br /> Now,if we are all married to Marge,that would make us all Homers.<br /> I'll have you know that I am not that simple.I have found ONLY 9 very definite,identical traits between me and Homer.It gets quite scary when you honestly count 'em.<br /> Back to the boat, I saw those fancy jack plates with the $400 price tag that are adjustable.While I want the speed,I don't need it at those bucks !.<br /> Thanks for hangin' in , guys<br /> I'll try to work out these photo's.Sorry,I'm borderline computer illiterate.But getting better.

 

[fireman57]

Re: A.V plate is 4.5in below hull...help!

Rosco good to hear that you are never satisfied and always wanting more from you boat. I made my own jackplate out of aluminum and used a 2x4 at the top for support and the extra 5 inches that I needed. Looked like hell but worked. You may be able to ebay one pretty reasonable. These guys are right. I like the jackplate with adjustable mounting holes. You will probably end up with the av plate about an inch above your bottom hull like I did. Keep going.

 

[ross patti]

Re: A.V plate is 4.5in below hull...help!

hey,guys...<br /> Good to see you back,fireman.<br /> I've been doing some serious ponderin' about this dilemna.I think I've found an answer,but to get the best input from y'all,I have got to pull my finger out and take some photo's,so you can see exactly what we're dealing with.<br /> While there are many good uses for a 2x4,my ego won't let my boat wear one.<br /> Technically speaking,does the problem get better the closer your AV plate gets to the desired position;or does the plate have to be above the keel before any improvement is possible ??? IE;will it improve a little if I get the AV plate to within say 1" ?<br /> Also , does raising the motor 5" have an impact on the steering cables,etc ??<br /> Some of the jack plates simply have mounting holes drilled. My motor only has 1 bolt hole on each side to mount it to the plate/transom. I would'nt feel too confident hanging the motor with just 2 bolts. At the moment,the screw in transom clamps are holding it all together,and I'm happy to keep it that way.{mmmm,2 fixing points no good compared to 2 fixing points. I think I need a beer}<br /> I'll take these photo's and post them hopefully tomorrow . till then,take care

 

[BillP]

Re: A.V plate is 4.5in below hull...help!

You want the cavitation plate clear of the boat bottom...at least 1/2". That's when you will eliminate major drag from the lower unit. Max speed is when the prop hub is only 1/2 in the water and you are propped right. I normally run boats at 2" above the bottom without a jp. First signs of being too high is cavitation in turns. If you want to run higher than 2" or so start looking at hyd jp systems and different props. The prop you use at 1/2"-2" elevation will likely be too small when raised to 5".

 

[Bear]

Re: A.V plate is 4.5in below hull...help!

Originally posted by rosco 11:<br /> The motor is a 35RL76 model. Ithink RL stands for really long !!.

<br />I think R stands for rope start and I know L stands for long shaft (20").

 

[ross patti]

Re: A.V plate is 4.5in below hull...help!

BillP,<br /> Thanks for your reply. I was with you till your last sentence. I need to raise my motor 5" to get the AV plate to 1" above the low point of the keel.I am not looking to raise it to 5" above the keel.I think at that height,the prop would have to be re-named to the fan.<br /> Bear,<br /> That whole RL business was supposed to be a funny.It will never happen again. Ironically,it is fitted with electric start,and the shaft length from AV to transom bracket is 22" ,so it still is really long.Hence my problem.<br /> Could someone please explain how to attach a photo to this posting ? This illiterate can't quite get a grasp of it. "a picture tells a thousand keystrokes "<br /> Thanks again,

 

[fireman57]

Re: A.V plate is 4.5in below hull...help!

Here you go Roscoe <br /><br /><br />

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