Boat won't plane out

[metriccrescentwrench]

Re: Boat won't plane out

.... For instance the "spun hub" scenario you mentioned. I'm not exactly sure where to make these marks (what is considered the hub?) .....

In general there's a splined metal bushing that rides on the prop shaft. That splined metal bushing is inserted into a rubber "hub" which in turn is pressed into the center of the prop. You'd make a mark with a felt pen that goes from the splined bushing, across the rubber, and onto the actual prop. After running the boat for a little while you can check to see if any of the marks you made have moved in relation to each other, if they have then you have a "spun hub" and you'd either need to replace the prop or else have the current one repaired.

 

[Chinewalker]

Re: Boat won't plane out

Your 8hp Merc is likely very close in power to your older 10hp Evinrude due to rating changes that occurred in the 1980s. The 8 should plane the 12-footer off smartly and with little effort. That leads me to believe that you either have a motor issue (prop and spark issues as discussed above) or perhaps a bottom issue. Is the boat's bottom true? .ie, is the keel straight? Nothing dragging overboard? A severely warped bottom might have some effect on planing ability.

 

[Olias]

Re: Boat won't plane out

Great stuff to know guys thanks. I will both check the spark plugs and try running on one at a time etc. I will also look into the hub situation. As a matter of fact when I was out the other day i was in a particularly bad area of the lake that is absolutely choked with weeds and when puttering through at a reeeeal slow speed there was a couple times that the motor revved up but prop not moving or pushing the boat. I mean for a split second. I assumed that was some sort of built in operation that helps not striping gears, breaking shafts or what ever when it runs into a situation like that. Yes/No? I of course immediately cut the throttle each time it happened (like 3 times) and once out of that area there was no problems or repeats of that kind of action what so ever. Mind you, this was the 1st time I was in that area of the lake and this has not happened before. So everything I have described up to now has nothing to do with this. Thanks

-B-

 

[nyx2k]

Re: Boat won't plane out

really does sound like you have a spun hub to me

 

[metriccrescentwrench]

Re: Boat won't plane out

... I assumed that was some sort of built in operation that helps not striping gears, breaking shafts or what ever when it runs into a situation like that. Yes/No?

The only option available that helps with those things is the experience of the guy driving the boat. Outboard engines just aren't that sophisticated.

 

[Olias]

Re: Boat won't plane out

FWIW.....I removed the spark plugs to see what they look like. Not sure what they should look like but they look like they are in pretty "normal" condition to me. I tried to take a close up but it's still kind of hard to see details. Any opinions?

I have not had a chance to check for spark or compression yet. Probably won't get to do that for a few days until my son comes over to help.

-B-

 

[speed_demon]

Re: Boat won't plane out

My brother has a similar 12" hull with a 5hp Honda and he had the same problem. Get yourself a tiller extension and sit up front. It's just too much weight in the back of such a small boat.

 

[Chinewalker]

Re: Boat won't plane out

This boat should NOT need extensions, fins, tabs, etc. to plane off with an 8hp. As I said before, an 8hp should be plenty to get her up on step with a properly loaded boat without having the take extensive measures to achieve it. SOMETHING is wrong with either the motor, the set-up or the boat.

Thinking outside the box a bit - is it possible the foam flotation in the seats is saturated? Could be possible if the boat ever sat full of water. Have you weighed the boat?

 

[Sea Rider]

Re: Boat won't plane out

General wild guessing, it's no good, a precious boating time loss. Start with prop hub test, probably that's the culprit. Had same issue with a 5 HP prop, bought a new one, made all the difference. Standard prop hubs, not the repairable new ones, are rubber heat vulcanized, not pressed. Have a time period use, are not eternal.

Happy Boating

 

[Olias]

Re: Boat won't plane out

Hate to show my ignorance but I'm still so new to all of this that I really don't know, but...Is the "hub" that everyone's referring to built into the prop? So if I get a new prop just to be sure, will that take care of any possible spun hub problem? Or, is the hub a separate animal that the prop slips onto? If so, that's pretty expensive isn't it? You'd have to take that to a shop to have someone install/press on, right? If the hub IS built in then maybe I could get a real inexpensive one lke this one Solas Amita Aluminum Boat Propeller #1111-093-09 for Mercury 8 HP Outboard 1986 - 2005 2-Stroke, Includes Merc 8 - iboats right here at iBoats just for testing purposes.

-B-

 

[JB]

Re: Boat won't plane out

Have you tried a hydrofoil, Olias? In my experience they will allow planing quicker and at lower speed. I have used them on several boats and always been satisfied with the results.

First, of course, you need to verify that your outboard is making full power and has a correct prop.

Worth a try.

 

[metriccrescentwrench]

Re: Boat won't plane out

Hate to show my ignorance but I'm still so new to all of this that I really don't know, but...Is the "hub" that everyone's referring to built into the prop? So if I get a new prop just to be sure, will that take care of any possible spun hub problem? Or, is the hub a separate animal that the prop slips onto? If so, that pretty expensive isn't it? You'd have to take that to a shop to have someone install/press on, right? If the hub IS built in then maybe I could get a real inexpensive one lke this one Solas Amita Aluminum Boat Propeller #1111-093-09 for Mercury 8 HP Outboard 1986 - 2005 2-Stroke, Includes Merc 8 - iboats right here at iBoats just for testing purposes.

-B-

Yes, the hub is part of the prop, it's the section in the center that the prop shaft attaches to. But before you even spend the money on that prop you linked to you could very easily determine if that is in fact the problem. Put a mark on one side of the prop shaft, and put a mark on the prop itself (the outer part. Go for a ride and see if the marks have moved in relation to each other.

 

[Sea Rider]

Re: Boat won't plane out

If you place a new pressed hub it will probabably work ok at fast idle, slow displacement speeds, this is a short term paliative, that same hub will spin while giving juice to engine when trying to plane the boat at wot. That's the differeence between pressed and vulcanized hubs on standard props. Go for the prop test and if found deffective buy a Solas prop with same pitch. Good luck.

Happy Boating

 

[Olias]

Re: Boat won't plane out

Ok, will do guys. That is, I'll mark the prop and hub and check it out the next time I have the boat out. Thanks!

-B-

 

[greenbush future]

Re: Boat won't plane out

have you tuned your engine anytime recently? The plugs looked good in color, but running some sea-foam treatment through your engine may help you achieve better or higher RPM's. Cleans all the carbon off the insides of your combustion chamber. All my gas engines get treated once a year, then I add to the fuel tank too. You will get a ton of white smoke, but follow the directions to the tee! It will run much more smooth after treating it.
BTW I think your biggest issue is the prop spinning based on what was typed here.