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Triming a pontoon

lakeliving

lakeliving

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Hi All, We had the boat out today and finally got some time on the motor so I figured I would give it some throttle. It seems there is some cavitation so here is my question. How do you properly trim a motor to avoid slip/cavitation on a pontoon? I did a search and didn't see anything. The boat is a 22 sslx (2) 25"toons with strakes. Thanks for the help!
 
Thanks Tom. So do you think the motor is mounted too high based on it slipping, getting air. Has anyone else come across this? I guess next time I have it out I'll have the wife give drive and try and take some pictures.
 
I couldn't say for sure. Cavitation is due to disturbed water, causing air bubbles around the prop for a variety of reasons. It just basically isn't getting traction at all times. I work through this stuff by eliminating things one by one and engine height is an easy one to see. You don't need to be WOT, just a nice cruise where it's planed out.
 
I'll take a photo next time we're out. I'll be pissed if this thing is not setup correctly.
 
lakeliving said:
I'll take a photo next time we're out. I'll be pissed if this thing is not setup correctly.
Click to expand...
I wouldn't be upset unless they did a lot of water testing on it (doubtful) or have put a lot of identical boats out there. That first setup of engine height and prop selection is really just a first pass, and the weight and distribution on the boats varies quite a lot depending on equipment. I think it's reasonable to need a bit of fine tuning.

I'm still checking my setup at 10 hours and will probably make a prop change at some point. I'd rather have at least 20 break in hours on it before I start worrying about it. At my insistance to get it delivered early, the dealer service guy water tested mine on a day that was rainy and 40 degrees, so I cut them a lot of slack.
 
Coming from a 40 HP pontoon with at least 1000 pounds less weight and no power trim, I had some confusing feelings driving this big rig for the first time. I probably was a little too proud and over-confident when the marine tech asked if I felt comfortable taking a loop while he waited at the launch and letting him know if I wanted him to get on board with me. After all, it was already 5pm on a Saturday, the weather sucked (I got mine the same day as you did Andy) and the dealer had rushed to meet my deadline. So, I did my loop, was a little intimidated, but I waved him off anyway. I definitely felt like the bow was a little high (which is to be expected I imagine) when taking off. Then, I still felt like the boat was plowing a little more than I thought it should when I was supposedly on plane. It was cold and windy/wavy, but it also felt like I was surging and bouncing a little more than I expected. I know it's going to take a little time to figure out my sequence of throttle and trimming but, like Andy, I couldn't help but to think maybe something was off. I'll be taking out again this weekend and will see how it feels. The tech told me that they have a template from the factory (Bennington or Evinrude?) that they place up against the transom and that's how they know where to mount the motor. If I'm still a little uncertain, I'll have to ask for someone from the dealership to take it for a ride. Lesson learned...take the test ride with someone who knows from the get-go.
 
Here is a photo with the motor down as far as it will go. Obviously I need to get it out on the water to see where the plate sits but maybe this will help until then. I notice the motor is as far down as it can go.
SAM_9033_zps127c7dd4.jpg
SAM_9030_zpsbfb1ba58.jpg
 
I don't think the engine pod is really a planing surface in the same way a middle tube would be, so it depends on where that is relative to the outside toons. You'd just need to see how deep the cav plate is when you're at a cruise speed with the trim mostly level (not tucked under, but not trimmed way out).

This is where we need someone like user "Ben & Suzy" or "CCanDo" to chime in. They have waaaay more expertise on this sort of thing.
 
I called the dealer on this as well and he said to start off with the motor all the way down. Then as your on the throttle start to trim up until you hit the sweet spot. Maybe I had the motor trimmed up to much when this happened? I'll still check it out next time on the boat. He also said that when you give it throttle, the motor wants to push down on the back of the boat while the lifting strakes are trying to raise it, thus working against each other. Makes sense I guess. He also verified that they have mounting instructions from Bennington on where to mount the motor. Hopefully this was the result of a newb behind the wheel!
 
Yes, could be over trimmed. I usually trim down somewhat for turning otherwise it'll slip.
 
Start in the trim down position, the trim up gradually as you give it throttle. Pontoons have a small trim range, triple tubes have a slightly bigger trim range, but not as big as a fiberglass boat. Find your sweet spot...you'll hear it and feel it kick out if you've trimmed too high. You may also want to trim down in a turn or when crossing a big wake. Sometimes people mistake cavitation with other issues. As a new boater, try trim first, then work with your dealer on the correct prop for your needs. There are LOTS of prop recommendations in this forum; propping is an art form. Good luck!
 
Thanks TB! I figured it was most likely a green horn at the wheel! I haven't built up the courage to try and pull it into the lift under power yet. One day!
 
I think you may have been a bit overzealous with the trim, that's all. The engine is already mounted in its lowest position, so too much engine height isn't an issue. Take TB's advice on the trim and get to know the characteristics of your boat. It should be just fine.
 
Wow, no wonder you have issues, the motors 1/2 way out of the water ...... :)
 
It is on a lift!!!! I guess looking back at the photos you can't tell.
 
Yeah, I was joking, but when I first saw the pic, I though you were trying to be funny, but then after reading, you were questioning the motor height. Then I saw transom way out of water and figured it out. Had me going for a second .....
 
Mine did the same thing. The dealer dropped it an inch, same problem. It actually ended up being an incorrect size/pitch prop issue. We went bigger and steeper, it got the boat into the sweet spot and stopped the slip.
 
I don't have the same model boat but I do have the same engine & twin tubes. I have found the trim range to be very small, roughly from all the way down up to 1/4 on the trim gauge (assuming all gauges are the same). I honestly keep it just a touch up from all the way down, I only get around 1/4 if I'm WOT in a straight line which for me is very rare. Our engine is mounted one hole higher than yours, do keep in mind different boat.
 
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