Anti-cavitation plate

[jimmyz1]

I have a 25 hp 1972 evinrude on a 14' 1958 crestliner that is in great shape. The one thing though on the boat is the transom is very low. Like you have to be careful when sutting down or using revese not to suck one in from the stern.

My question is should the anti cavitation plate be even with the bottom of the boat when the boat is on the trailer. Seems like when boat is in water motor is very low in water. Motor is a short shaft. Owners manual just says when running the cavitation plate should be parallel to the boat. If the motor is sitting to low on transom could it lead to less performance? When on trailer the cavitation plate is about 1 1/2 inches below the bottom of boat.

Thanks for any input or thoughts.

 

[GreatRiverDucker]

Re: Anti-cavitation plate

yes the anti cav plate should be within an inch either way of the bottom of the boat, I've used a thin piece of wood between the transom and the motor to raise the motor 3/4" or so hope that helps
btw is it a sportster I have one and if I could keep it running it would be a sweet motor

 

[F_R]

Re: Anti-cavitation plate

For best performance, raise it as high as you can without getting cavitation/ventilation/sucking air. Do it by temporarrrily putting sticks of wood on top of the transom to jack it up. You will know when you get it too high. The 25 lower unit design is not the world's most efficient and the anti-cavitation plate will need to be around an inch below the bottom on most boats.

 

[jimmyz1]

Re: Anti-cavitation plate

Thanks for the input. Yes it is a sportster. Mine does run sweet and idle's great, but has a lack of power I think. I use it for duck hunting and maybe I'm just loaded heavier than I think. Thanks.

 

[MikDee]

Re: Anti-cavitation plate

"Sportwin" you mean right?

 

[F_R]

Re: Anti-cavitation plate

The 25 was a Sportster. Sportwin was 10/9.5/9.9hps

 

[BoatBuoy]

Re: Anti-cavitation plate

The other posters are heading you in the right direction. However, the anti-ventilation plate has nothing to do with the height of the transom above the water when sitting still. That is determined solely by weight at the back of the boat.

 

[jimmyz1]

Re: Anti-cavitation plate

Well the transom sits low cause almost all my weight is at the back of boat. I try to put decoys and other gear up front but it still sits low cause I have to drive boat from back seat. That's why I think I need to raise motor a little cause with the weight in the back of boat I think the motor is staying deeper than it should. I could be all wrong.

It just driving me crazy that this motor isn't pushing the boat as fast as I think it should be. I know there is no fast screw on the carb. and it is set. Could there be a problem here. I've had carb. off and completely cleaned out. Looks good. My friend has a 25hp johnson on a 16ft. jon boat for duck hunting and he could drive circles around me if he wanted.

 

[GreatRiverDucker]

Re: Anti-cavitation plate

have you checked compression? what about the plugs, do they both look ok? let us know.

 

[jimmyz1]

Re: Anti-cavitation plate

Brand new plugs, gapped properly. Compression test no. The motor does run absoulutly great. Starts easy, idles low great, sounds great when opened up, doen't have a miss in it. Could it run good with bad compression? Just seems like it should and like it wants to go faster. If it could be compression would it run way slower than it should?

I think I'm getting to the point of taking it someplace but duck season opened yesterday so I don't want to be without it. Spare motor is a 10hp 1956 sportwin that runs great but isn't enough motor now. I added a cabelas blind to the boat and that's the reason I went up to a 25hp motor.

Thanks!

 

[GreatRiverDucker]

Re: Anti-cavitation plate

Sounds like a nice setup, where do you hunt ducks? I'm in northern MN. Yes, if it has low comp it might run alright except with less power. Buy a comp tester at advanced auto or similar store $20-30. Ideal is like 110+ psi per cyl if it is significantly less than that you may have a blown head gasket?
Btw my 25 would push my 14' starcraft with blind and two guys pretty well, say maybe 20mph(when it was healthy)?

 

[GreatRiverDucker]

Re: Anti-cavitation plate

Plugs should be champion J4C or equiv

 

[F_R]

Re: Anti-cavitation plate

There is nothing wrong with the carb, or the rest of the motor if it runs as good as you say it does. Play with the height and trim if you want to, but don't fix something that ain't broke. It really does sound like a weight problem from here.

 

[MikDee]

Re: Anti-cavitation plate

Sportster, Ok,,, Is your timing advance working?

 

[jimmyz1]

Re: Anti-cavitation plate

Sounds like a nice setup, where do you hunt ducks? I'm in northern MN.

Southeastern michigan. Right over the MI -OH line. I live in Ohio. I'm about 15 minutes from MI. A lot of my hunting is from Erie MI to Monroe MI. Mostly marshes right off lake erie. Not that the water gets real big but it's nice to have a little extral power in Maumee Bay when u need it. Can get a bit swelly in there with east winds. Mostly it's protected from lake erie by woodtick peninsula. I usually stay on the inside of that and there are other islands and marsh land. It butts right to Erie gun club which is a private marsh that is big and been there forever and they take care of it really well with ton of good eating vegitaion for the waterfowl.

I may check the compression but think I am going to leave well enough alone and be happy it's running good.

Thanks for all the replies.

 

[60 grit sandpaper]

Re: Anti-cavitation plate

why not check RPM's

 

[GreatRiverDucker]

Re: Anti-cavitation plate

hey jimmy you say that you think that it's not giving you all that it should. Like I said before my 25 would push my 14' about 20 mph or so which was pretty good, it was a little slow up to plane but then it scooted right along. As for the weight issue, is your tank as far forward as it can go? Are you getting it up on plane? I think it should be able to push you pretty well, depending on how heavy your set up is? Maybe one of the experts can tell you how to set up a tach to check your rpms? And I don't think that it could hurt to find out the comp, if you find out it is low then that might be the issue.

 

[GreatRiverDucker]

Re: Anti-cavitation plate

Oh hey I just thought of something. Have you looked inside the cylinders, through the spark plug holes, is there a lot of carbon built up? If so you should do a decarb - check the FAQ, you should probably do it anyway.

 

[jimmyz1]

Re: Anti-cavitation plate

I'll check that out and probably do it. I went hunting today just me and the dog. It ran great. Started on second pull. I was happy with the speed I was going. She planed out great and cruised great. Maybe just hitting the weight a little much. Next time someone else is with me I'm going to put them in the middle of the boat instead of the bow. I think with decoys and person up on front seat the boat is plowing to much causing more restriction for the motor. Thanks

 

[iwombat]

Re: Anti-cavitation plate

might want to set your tilt pin a hole or two out if you think it's plowing in the front.