Boat will not get on plane.

[usnscc_johnson]

Trying to get some help. I'm new to this forum and new to the boating world. I have an 89 Bayliner Trophy 21'. It has a Ford 351 engine with a OMC outdrive. I had the boat out a few weeks back with just myself and one other person. I launched in a large river mouth the boat ran great against and with the current. No problems getting on step. Ran pretty easily about 25 MPR with Last weekend I launched out of a ocean harbor with little current and water like glass this particular day. A little more added weight. On the boat was three grown adults and 2 young children a little bit of fishing gear and about 25 gallons more of fuel. Not a crazy amount of additional weight. Yes I ran the rain water out prior to the launch. I insured the trim was ALL the way down. I could not get the boat to plane out or really get over about 8-9 MPR. Everyone moved toward the bow which helped a little to get the bow down but did not get me on step. In attempt to push it a little harder to get on plane I ran my RPM's up to around 5000 which caused my engine temp to get a little high. At slow speed the only issue I seemed to have was the steering would drift back and forth slightly causing me to constantly correct but I don't think the two are related. I'm thinking a spun prop. Is there any way to check with out the boat in the water. Visually doesn't look bad. OR is there anything I'm missing? What else could cause this? As I said I'm new to this. Thanks in advance.

 

[Chris1956]

If you ran the motor at 5000RPM, and she only moved 9MPH, you have either a spun prop or a bad engine coupler. You can add matching marks to the prop hub and prop and take her out again. If the marks do not line up, the hub is spun.

Of course, you could also use a known good prop and test it.

BTW - I doubt your redline on that motor is 5000RPM, so you might take it easy, so as not to damage the motor.

 

[usnscc_johnson]

Forgive me as I said still learning. Could you give me more info on the engine coupler? How can I trouble shoot that? As far as the spun prop idea I have made the marks unfortunately it's a task to get it in the water but I have a plan. That seems to be the only way to test it. My tach goes higher than 5000 but the numbers turn red above 4500 range. I did not run it for very long in the red. Also I did not noticeably hear the prop slip. Is that normal? Or would I likely hear it slip?

 

[Scott Danforth]

Your goung to have to pull the boat, then remove the drive to remove the motor to get to the coupler

 

[porscheguy]

Rule out the prop before losing sleep over the coupler.

 

[Faztbullet]

Prop...coupler...gears in upper drive need checked

 

[jimmbo]

WOT Rpm range is 3800 - 4200

 

[usnscc_johnson]

Thanks all. I will test the prop first. Hopefully I will not have to pick that motor out.

 

[usnscc_johnson]

So guys I took the boat out this morning. On a lake this time. Unfortunately about 250lb lighter. And to confuse me even more the boat got right up on plane no problem. Prop didn't slip any. I don't understand why I couldn't recreate the problems. Also while looking for a new prop, all the prop sites recommend a 14.25x17. Both the current outdrive and the spare I have has 15x15 on them? Could I get some opinions on this?

 

[Sea Rider]

On previous water test if load was badly distributed on deck, badly trimmed or a combination of both cases, combo will have hard time getting on plane.

Before going for a new prop, need to check if prop is doing its homework right, could have prop with issues, say on its way to become spun. If OK make 2 wot runs, as usually loaded and a solo run, report max rpm achieved on both cases to see if engine runs inside safe wot 3800-4200 rpm range as stated by Jimmbo.

What prop sites recommends is just a recommendation, say a prop starter, doesn't mean is the prop the combo needs, for that will need to dial one under trial and error that suits best your boating needs. A 17 pitch prop will lower actual wot rpm range achieved with a 15 pitch prop.

Happy Boating

 

[usnscc_johnson]

I will try this and report back. Thanks. This question seems crazy but would the ocean salt water with Alaska tide currant make a significant difference from a fresh water lake with almost no currant?

 

[AShipShow]

Coming from the restoration side of things and knowing what I know about older Bayliners, curious if you could measure the draft of the boat or get it weighed... Factory weight with standard engine (3.0L) for that boat is 3450lbs probably plus a couple hundred for the 351. Or, draft (exluding drive) is 1' 7".

Just wondering if its got an extra 800lbs of wet foam and wood under deck.

 

[jimmbo]

I will try this and report back. Thanks. This question seems crazy but would the ocean salt water with Alaska tide currant make a significant difference from a fresh water lake with almost no currant?

Salt Water is slightly more dense than Fresh Water, so the boat will float higher and could in theory cause less drag on the hull, however the higher density will make make for slightly more drag on the lower unit. The ocean is at sea level, but at what altitude is the fresh water lake? That could affect the power output of the engine.

A boats speed can be measured by its progress against the Water, the shoreline, the lake/river/ocean bottom/GPS and they may not all jive. A current, as you are concerned about will affect shoreline/bottom speed, but not the speed the boat is going in relation to the water