louder but not faster HELP PLEASE

[joeyd50]

18.5' Bassboat, 1974 Evinrue 115HP, 13-3/4X 15 Aluminum prop, The boats gets on plane supper quick and at about 1/2 throttle it will cruise on plane at about 20mph if I go WOT it just makes more noise but doesn't go any faster, every now and then it seems to kick in, sound better and begins to pick up speed and then gets louder and slows down. It also sounds like a slight miss when its running loud. Plugs are good, compressing good.
Thanks
Joe

 

[Bifflefan]

Re: louder but not faster HELP PLEASE

Spun prop hub???

 

[ezeke]

Re: louder but not faster HELP PLEASE

Remove the ignition coils and thoroughly clean the ground where they connect. If the ignition coils are cracked, distorted, discolored or melted, they should be replaced.

Check the ground connections for the rack that holds the coils and powerpack; the rack has rubber mounting grommets and a good ground connection sometimes is lost. Check the grounding straps for good connections.

The easiest way to locate the ignition problems is to run with an inductive timing light - you can read each cylinder across the wole RPM range with a helper to drive the boat.

Check that your propeller is not losing bite at speed - you may have cavitation or ventilation.

 

[lmuss53]

Re: louder but not faster HELP PLEASE

It sounds like the prop is letting go of the water. Try trimming it down into the water a little more. Don't run it that way, it will tear the motor up. Think of it as running your car wide open with the clutch slipping. If you don't have tilt and trim try letting the motor down another hole on the trim pin. There is also a chance that the prop hub is spinning in the prop, but that is unusual unless you hit something.

 

[Craig-]

Re: louder but not faster HELP PLEASE

every now and then it seems to kick in, sound better and begins to pick up speed and then gets louder and slows down.

Thanks
Joe

Is it gaining rpms at this point?

 

[G DANE]

Re: louder but not faster HELP PLEASE

You do not mention how heavy your boat is, but it seems to me a 115 on a 18,5' boat should be able to turn a 17 or even 19 inch pitch propeller. What are your maximum rpm s.

 

[bilbo1usa]

Re: louder but not faster HELP PLEASE

It sounds like a spun prop. I had the same issue, especially when my prop was going bad, but not entirely damaged; fine at lower RPM, then at WOT the RPM would raise, but the boat wouldn't go any faster.

An easy way to test: when the boat is out of the water, put it in gear and try to turn the prop. As your prop might be only slightly spun, it may take a little muscle to turn it. Look at the propeller shaft. If the prop shaft isn't turning and the prop spins a little, your prop's hub is spun.

Don't confuse that movement with you turning the motor and prop shaft from the prop. Make sure the prop shaft is not turning if the prop is.

FYI propellers have a rubber hub inside that acts as sort of a shock absorber. This rubber can break away from the metal hub that contacts your propeller shaft, and the shaft will spin, but not the prop.

It's the easiest thing to check.

If that isn't it, then try the other suggestions, they're all good ideas as well.

Bill

 

[samo_ott]

Re: louder but not faster HELP PLEASE

Spun prop or dropping a cylinder. An easy way to check for a spun prop is to remove it and draw a line across the hub on the inside. Then replace and run it. Then remove it and check the line. If it has moved, it's spun.

 

[joeyd50]

Re: louder but not faster HELP PLEASE

WOW, thanks for all the suggestions, I'm going to try a new SS 13 X 19 prop, the boat according to the manual is 1200lbs, I'll move the trim pin down and try it, I'll try these before we get into the money items.
Thanks Again
Joe

 

[ezeke]

Re: louder but not faster HELP PLEASE

You don't have to remove the propeller to check if it is spun, just scribe a line across the hubs, using the cotter pin as a pointer. If the line moves while running the bushing has slipped.

 

[joeyd50]

Re: louder but not faster HELP PLEASE

I had a 85hp Johnson on this boat with a 13 X19 prop that I busted up, I got this 13-3/4 X 15 for $10.00 at a yard sale, it push my boat around 30mph. The 115 Evinrude was my sons motor, I have a SS 13 X 19 I'm going to try. According to Michigan Wheel it should have a 13 X 19
Joe

 

[Craig-]

Re: louder but not faster HELP PLEASE

I rpms gain with no increase in speed, motor is spinning up, prop isn't. Which is the louder you hear. Do you have tach gauge?

 

[joeyd50]

Re: louder but not faster HELP PLEASE

I rpms gain with no increase in speed, motor is spinning up, prop isn't. Which is the louder you hear. Do you have tach gauge?

I do have a Tach but I don't remember looking at it, my bad, I will look next time.
Joe