woodguru Loc: El Dorado Ca

Okay, so I noticed a problem right off, I think I said something. The prop was cavitating under a couple of conditions. It would take almost no trim without the prop catching air and increasing the RPM's.

4000rpm and a turn under power would cavitate and the rpm would surge by 1000rpm

Going over easy wake would cavitate the prop with a surge of increased rpm

Worst of all was the way it was so hard to turn to the left, easier to the right, it was hard enough I didn't want my wife to try to drive it.

So the engine was mounted one bolt hole position higher than the lowest setting, so the dealer lifted the engine and put it in the lowest hole...

Much much better...steered easier although still not like it should be, indicating the propeller still needs to be deeper in the water.

Still cavitates although I can trim it a touch better

If I'm cruising at 3500/4000rpm and hit the throttle it jumps to 5500 rpm as it cavitates, and settles in at the 5300rpm that it seems to be electronically limited to no matter what size prop I try (another issue they are going to adjust for me). The engine runs really strong and has great acceleration, but it should not cavitate like it does.

So straight up, this 20 inch shaft outboard is flat out not the right motor for this boat. The 25 inch shaft could be set about two inches higher and get the prop three inches deeper in the water, which would be very close to just right.

On one hand I could probably live with how it performs, but not right is not right and not getting the full trim ability and prop depth so it isn't over revving under different circumstances isn't acceptable. I have noticed that other manufacturers often equip this 18 foot sized boat that has a 20-1/2 inch transom height with 25 inch shafts.

I'm wanting to hear some perspective over whether this is worth going after the dealership, Mercury will give me a really good under wholesale price on the longer shaft extension, which would be somewhere around $3500 at full price.

woodguru Loc: El Dorado Ca

This could be a marketing nightmare for Lowe if it widely got out that there was a serious performance issue with the short shaft motor these have been sold with...which makes them a candidate for making this right.

FishermanLeeSonoma

Definitely go after dealership for selling you the wrong set up. Sounds pretty shady. Might contact other dealerships and mechanics for some more information.

Lowescatfish18 Loc: Wesley Chaple florida

ok i really must of miss your 1st pose i have a 18ft lowe catfish model with a 115 murcuy i did have a issue with
jumping up out of the hole it use to raise bow up and never get on plane so i change the prop to ss 3blade and now
it jumps up with no issue and run around 45 miles per hour around 5500 rpm. if i try to push harder the bow starts to bounce up and down the only way i can go faster is put water in the front live well so the weight helps it stay on to
plane but the gas use is not worth it. this is a 2018 model.if this helps let me know i'll go out to the barn and get the
prop size cost last year was 300:00 dollars.




tight lines

Fredfish Loc: Prospect CT.

The anticavitation plate should be just below the bottom of the boat. If you lower the prop 3"deeper in the water, you'll be dragging more of the leg in the water, cutting your speed and fuel economy at all RPMs. That's why Jack Plates were invented, to fine tune the prop depth, for minimum drag /maximum speed. The transom height for a long shaft motor (20") should be 19"-20". The 20.5" transom is part of the problem.

nutz4fish Loc: Colchester, CT

wg.... Now, you're getting to what can be accomplished via the dealer with manufacturer's support and encouragement. And THEIR $$s . I understand little about gas propelled boats, but it sounds to me like Fred is onto something. Bad initial transom design ? And filling the live well to keep the bow down ! I Had a 9.5 hp Johnson on a small pond boat, and that's it for me except for electric trolling motors. BassTender is the biggest craft I've owned. But... I bought plenty of gas,bait, & lunches to pay my way & not be a total freeloader. Saved a bundle on taxes, bigger tow vehicles, higher registration fees and such, that others had to pay, leaving plenty to buy the beer after the fishing was over for the day or night too. Win/Win. ( unless I'm giving myself too much credit ). Good Luck Man, don't let 'em wear ya down...

DocB Loc: Bama

Fred, it's been awhile, (my ranger seems to be set up well from the dealership) but if I remember correctly, when we set up a jack plate, we used to start with the cavitation plate 3 inches below the running pad and adjust from there... My last boat I took to the lake and moved the motor in 1/2 inch increments until I found the optimum settings for both of the props I had for the boat.. If his cavitation plate is not somewhere just below the running pad, or bottom of the boat, he needs to either look at a longer shaft, or he may be able to drop his motor with a jack plate.... The steering problem should correct itself when he gets the hight of the motor right, and is able to get the proper lift on his hull...
Doc

Fredfish Loc: Prospect CT.

Hi Doc. The few guys I know with jack plates on their boats, run chopper style props, and low water pickups. They run with their cavitation plates higher than the bottom of the pad, once they're up on plane.

DocB Loc: Bama

Fred, when you get the motor at the right hight, when you trim the motor up the cavitation plate will be at or just above the water level... What I was talking about is your starting point for your set up.... With the boat on the trailer, adjust the tongue jack till the boat is pretty well level, with a straight edge, set the height of the motor where the cavitation plate is 3 inches below the pad with as much adjustment as possible both up and down... This is your starting point for a manual jack plate... From here you have to run the boat and make small adjustments up and down till you find the optimal hight for the motor with the prop you are running. It usually takes several trailerings and adjustments to find the optimal hight, when you do, I recommend scribing a mark on the jack plate in case you move the motor at a later time... There maybe an easier way, but this is how we set them up for a good balance between hole shot and top end. With power jack plates, I must say I have never set one up, and have little experience running them.... I haven't ran a chopper in years, my Dad ran a 2 blade chopper years ago, and I remember the set up being very touchy, I run 3 blades, I am more than happy to give up a few miles per hour to get out of the hole in shallow water...
Doc

Fredfish Loc: Prospect CT.

The guys I know have the powered ones, and after they're up on the pad they run 1 of the 3 blades out of the water. That's why they have the low water pickups. They get another 5+mph top end that way.
If my next boat has or needs one, I'll learn to tune it then. Thanks for the information, I'll save it for the future.

DocB Loc: Bama

Fred, I out grew my "need for speed" years ago when I found a stump trying to get out of the hole on a shallow flat... I was lucky, all I did was take a couple of inches off an ear of my prop, (and da*m near soil my pants)... But you are absolutely correct, about running as high as you can on top end, the more foot and prop you have out of the water, the less drag you have... And the less drag, the more speed you have... I'm not an expert on setting them up, this is just the process I was taught years ago, and once again, this process might not be the easiest, or even the best, but it does work for an "all around" set up... Doc

Fredfish Loc: Prospect CT.

Thanks again Doc, I'm trying to outgrow it too, but I'm not there yet.

DocB Loc: Bama

Wg, I know Fred and I got off on a side discussion on your post (and Fred has a very valid point about how drag effects your top end), I hope our discussion gives you some ideas to look at... You mentioned Mercury offering an extended shaft at about $3500. If you can't get the dealership to help you get it right, I would suggest looking at a manual jack plate to drop your motor where it needs to be... Make sure and do some measuring to make sure the mounting holes will allow you to get the motor down to the proper height... If you can get your motor where you need it, it would be way cheaper than the 3500, (probably less than $500), and could help the performance of your rig... Just a humble suggestion... Doc

DocB Loc: Bama

Fred, good discussion, that's what I like about this forum, and why I come back...
Doc

Whitey Loc: Southeast ohio

Is this a NEW boat if so they would be making it right. I'm sure you payed dearly so make them make it right. Dealership an Lowe's need to be talked to about this