Why the low power???

[BigBassin78]

I cant tell if I have an issue with my motor, or if it is with the setup of my boat. I have a 16ft Hurst fiberglass bass boat 78 model with a 78 Evinrude 115. It is a relatively light boat, I would guess that is is about 750-900 pounds dry, with me and my buddy, fishing gear, and fuel about 1100. When I am out by myself the boat pops up on plane without hesitation it will run about 50-52 at 5800 RPM. Add my buddy and a little more fuel and it wont plane or reach more than 3000RPM without him getting closer to the bow, it will run 47-48 at 5800 RPM. Here's the kicker, sometimes it will get up on plane without him moving towards the bow!! The motor seems strong and runs like a top, but why wont it plane sometimes with just a little more weight.

I just feel like 115 should be plenty to push my little 16 footer out of the water,

info: prop does not have stamp, so I do not know the prop specs. The motors standard prop size is 19" pitch by 13" diameter, Im sure the prop that is on there now is not anything higher than 19" pitch.

 

[BigBassin78]

Re: Why the low power???

thank you for any input!

 

[iwombat]

Re: Why the low power???

Well if you're running 5800 RPM at all you're propped right. You've got something robbing you of power. Could be a waterlogged boat. Do you have any way of checking the flotation foam under the deck? If not, weighing the whole rig at a weigh station my provide some insight.

Barring that a spark and compression test is probably in order. You might have a dead cylinder stealing torque from you.

 

[BigBassin78]

Re: Why the low power???

i have checked for water logging, all ok there. Have also checked spark, ok there too. cylinder compression is 123 123 125 124. Its the whole intermittent thing that has me scratching my noggin.

 

[BigBassin78]

Re: Why the low power???

Well, well, for some odd reason today I looked down the exhaust ports through the prop. Low and behold, A PROP SIZE STAMP. So, the prop reads, 21 X 12 3/4. My engine is rated for no more than a 19 X 13. I don't believe that the 1/4 inch drop in diameter warrants the 2 inch increase in pitch. This is why I am having an issue getting my boat on plane. It simply takes too long to plane. Granted, it is fun going 52mph on a 16 foot bass boat, but I thought it might be a little fast for a 115.

Weird thing is though is that I was still getting between 5600-6100 rpm depending on trim position with the boat being over propped, makes sense that it couldn't hit more than about 2900 until it hit its plane. I will report back when I get the "proper" prop..lol

why do people do this, over prop the engine that is.