Boat won't plane.

[Craig_B]

Source of the post Definatley going to start with the Tune Up route first. Probably never been done.
However. For my own knowlege, what is the best position for the stern drives and tabs when one wants the boat to plane?
Fully retracted then adjust if necessary? I am completely unfamiliar with their function, well not completely but assume I am

Thanks

Make sure new fuel filters are part of the tune up and when you take the old ones off, drain them into a glass container. What you see could possible be a real eye opener. Ask me how I know

OK I'll bite. How do you know?

[buster53]

Ok, my port engine was running very rough. Drained my filter and it was 90% water and a lot of trash. Ended up pumping out my tanks and it wasn't pretty...actually downright ugly.

[ColRon]

Source of the post For my own knowlege, what is the best position for the stern drives and tabs when one wants the boat to plane?
Fully retracted then adjust if necessary? I am completely unfamiliar with their function, well not completely but assume I am

Thanks

Craig, there are two schools of thought on trim tabs. Some like above, fully retracted then us to trim out after your up. Bennet, a major manufacturer of tabs, recommends to start out with them fully extended or in the down position. The thinking is that this reduces bow rise and helps bring the rear of the boat up quicker, therefore resulting in the boat getting on plane faster.

Now that said, which is the best way, I don’t know. I’ve tried both ways and while it does reduce the amount the bow will rise when coming up on plane, I can’t say that it makes it any quicker as I’ve never truly tested the theory. But by experimenting with both your drive trim and your trim tabs you can find what’s works best for your boat and improve your speed at a lower rpm

[Craig_B]

Update:

There is not enough summer left for me to F around with the performance issues so I had the mechanic at the marina have a look.
He discovered corrosion on the caps and rotors and indicated like many others here they should be replaced.
After they replaced those items he took it out on the lake and reported it got up on plane and reached 4200 RPM.

One weird thing he also noted was that both trim tabs where down. I put both of them up and shut off the breaker to keep them that way last time out.

How could they move to the down position on their own?

Any ideas??

Thanks.

[Viper]

Source of the post Update:...corrosion on the caps and rotors......After they replaced those items he took it out on the lake and reported it got up on plane and reached 4200 RPM....

Source of the post.... One weird thing he also noted was that both trim tabs where down. I put both of them up and shut off the breaker to keep them that way last time out.

How could they move to the down position on their own?....

They can't unless you have a switch or pump solenoid that's sticking. There's a spring in the actuators that returns them to the retracted position when you push the button to retract them. Are you sure what you were doing was retracting them and not the other way around? Does the switch panel have arrows on it or a graphic to indicate what each button does to the bow (lift or lower)?

[km1125]

Definitely check the switch panel orientation. Once after I had done some work on my dash I had trouble getting up on plane without plowing. Drove me crazy. Even had someone go under my boat to look at the shafts and props to see if something was wrong. Found out when I thought the tabs were up they were down because the switch had been flipped upside down (by ME!). Flipped it back the way it was supposed to be and everything was fine.

DOH!

[buster53]

As said above, are you sure you are operating the tabs correctly? Depending on how the switches are marked, sometimes you have to stop and think which way is up and which way is down.
My switches don't say tabs up or down, they say bow up or down, which by the way is the same...bow down = tabs down.

[Bandit]

3000 rpm at wot sounds too low for a gas engine. Check the Merc specs but I would expect 4000+ therefore items suggested by others such as distributor springs, timing , overwheeled, carbs gummed etc come to mind. Also, how old is the gas ?

[buster53]

Source of the post 3000 rpm at wot sounds too low for a gas engine. Check the Merc specs but I would expect 4000+ therefore items suggested by others such as distributor springs, timing , overwheeled, carbs gummed etc come to mind. Also, how old is the gas ?

The OP said, after the mechanic worked on the engines, test run got up to 4200.

[Craig_B]

I know the tabs where UP when I switched the breaker off. I was under the boat with my mask looking at them.
I wonder if maybe the breaker isn't actually hooked up to the tabs?
Either way I guess I am going to have to monitor them for a while.

Thanks everyone.