Cavitation plate - Page 2

Michael Vezzosi · #11 12-10-2003, 08:59 PM

Capt. Brad I can check my 79 20 MA tomorrow and reply on Saturday. New Johnson 175 in '99 and duplicated transom in y2k because motor was short shaft. Motor turns about 5600 trimmed up, but not sure of speed with GPS. I can tell you that I'm always in 278 feet of water at that speed though!?!?!?! Maybe I should drill MOOOORE holes in my beautiful factory hull to cure this, huh?

Briguy · #12 12-11-2003, 10:56 AM

More than likely you have a fowled plug. Spend 10 bucks at the local auto parts store for a new set and see how she goes. It probably wouldn't hurt to dump 20 gallons of 93 octane fuel in, replace your fuel water separator and add a can of carb cleaner, too. It's amazing, just dropping one cyl can really slow you down.

Briguy · #13 12-11-2003, 02:33 PM

Capt. Brad,

Watch out for Havoline oil. I had trouble with fouling plugs on that stuff. IF you have access to a glass beader that's the best way to clean plugs.

barnacle · #14 12-11-2003, 08:22 PM

I would call your mercury dealer and see if you can run the gapped plug. Some Johnson and Evinrudes call for the non-gapped plug but going over to the gapped plug they run so much better. Note you will not find this on paper and you need to be sure the dealer has a good background when it comes to service. If your transome is 27" and your not catching air and your staying cool then your not to highHow I like to check is go into a hard turn. If you rpms dont climb then you should be ok. If they do climb then chances are when you get into some seas you will slip like crazy.

TUGBOAT · #15 12-12-2003, 01:53 AM

Yep ! I think because the oil mixture was HIGH it fouled them even though it only takes bout 10-15 min.to get out the channel,Hooked it up & noticed the diff. I beleive I even cut the channel that day so maybe 8 min. running. Had NEW GAS,Plugs(NGK-no gap),water seperator,carbs were cleaned,everything was changed to new or cleaned . Hopefully this weekend it'll be checked pretty hard.From the keel to the top of the transom is approx.27"s Its a 25" shaft.
This is still bugging Me also.
Scream'n Reels' [img]images/icons/confused.gif[/img]

Michael Vezzosi · #16 12-13-2003, 12:14 PM

Capt. Brad, had a chance to check my cav plate and it appears to be very, very close to flush with keel. For whatever its worth...