Help with what I think is porpoising on a 2010 Sylvan w/ Evinrude Etec 75

[trickynick]

What is happening is that I cannot trim the boat without it hopping in the water. When i begin to accelerate the motor is all the way down as the boat get on plane and i try to trim the motor the boat begins to hop violently at which point i have to trim all the way down to gain control. I just recently changed the prop to a 3 blade aluminum 13.5 x 15 it was a solace 12.75 x 17 4 blade aluminum prop. The Rpms with the motor all the way down were 5900-6000 WOT which I know are high for the motor but I would like to cure the hopping first and be able to trim the boat properly to see what the true RPMs are. The only thing I can think of is the height of the motor, it is at the second hole from the top, just not sure which way to go either lower it one hole down or raise it 2 holes up and I have been getting different opinions of which way to go from the marinas here in Ontario.

 

[southkogs]

Welcome aboard Nick:

What is the max HP your Sylvan is rated for? I'm assuming this is a bow rider? Maybe a little more boat information would help out.

 

[trickynick]

The max hp the boat is rated for is 90 HP. The center line is 16.5 beam 88. Aluminum boat. Not a bow rider. Took it out last night in a bay and found if someone sat in the front it trimmed fine so I'm thinking trim tabs but am open to any suggestions

 

[southkogs]

Tabs'll help I'm sure, but it may be a bit early to invest in those ...

If you're talking about the trim of the motor being set at the second stop from "ALL UP," then I would say drop it "ALL DOWN" and see what changes. If you've got power trim, then I would play with that. Sounds like you may just need to trim the motor out.

 

[garbageguy]

A couple pictures would help you get better information. Agree with the above, adjust down - and check weight distribution

 

[82rude]

If your etec is anything like mine the trim is very fast!Ifound on my boat that a couple of seconds was all it took for perfect trim. Any longer and id get porpoising then blow out next.Its the fastest trim ive ever used so it doesn't take much to trim perfectly just a tap or two.

 

[trickynick]

The problem is that with motor all the way down the second I attempt to trim up the boat begins to porpoise I then have to lower it back down to get a smooth ride but the steering tough

 

[trickynick]

I also tried to move the motor the highest up that the motor would go it was a better hole shot but the second the bow comes down and I start to trim the motor it starts to porpoise again but if one of us go to sit at the bow the problem goes away. I have in invested in the smart tabs hopefully going to try them out tonite. Will let everyone know how it goes. I thank everyone for there help

 

[trickynick]

Just a update. I purchased installed and tested the Nauticus smart Tabs today and all I have to say is WOW. On setting 3 the boat has almost no hull lift from the hole shot and it planes out beautifully and best of all the porpoising issue is gone. Thank you to everyone for your suggestions and I look forward to talking to you on iboats

 

[82rude]

great.they did the same for me years ago with a glass boat I had.still,you had a issue that shouldn't of been that horrible and I wonder what the root cause is ?on my boat it was the foam under the floor which was totally wet and added lots of weight to the boat.

 

[trickynick]

I think it was just weight distribution. The gas tank was closer to the back also from what I am reading sylvan and smoker crafts seem to have the problem.