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Need Help - Only getting 4100 RPM @ WOT
Posted: Mon May 21, 2018 9:05 am
by andymul87
Hi All and thanks in advance for your help!
I just repowered from a 2008 F115TLR to a 2011 F150TLR. First time on the water was this past Saturday and I was only getting 4100 RPM at WOT. The 115 was getting about 5000 WOT with a Solas 13.5" 15P SS prop. The 150 has a Solas aluminum 14.5" 19P. I know I need to move down in pitch, but pitch wont get me the 1700 RPM I need, will it? What else should I look into? I'm definitely calling the dealership today to see if they know what's up. What questions should I be asking them?
Let me know if I'm leaving out any details necessary.
I'm pushing a 2008 South Bay 825CLR with two toons.
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Mon May 21, 2018 11:41 am
by Soonertoon
You have waaaaay to much pitch on that prop. You should be in the 51 to 6K range at WOT. Id drop to a 14 P to start.
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Tue May 22, 2018 2:05 am
by wwind3
Interesting.... the 115 rpm's are low too. What boat are these motors on? A pontoon is a lot like pushing a dumpster thru the water. Is yours a tritoon? If your props are working that hard all the time you will probably spin out your hubs in short order.. Mercs usually run in the high 5000's. My 90 redlines at 5850 approx. Good luck.
Oh--make sure motor isn't set too deep in the water. Cavitation plate should be even with bottom of center mounting pod.
btw--I'm running a 13 x 16 pitch on mine- I had it repitched to 17 and lost about 350 rpm's and some speed-so I switched it back. I am running a 3 blade prop....
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Tue May 22, 2018 9:16 am
by FLOUNDERPOUNDER225
Agree with Soonertoon, 14.5 X 14 pitch..
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Tue May 22, 2018 10:46 am
by andymul87
I talked with my dealer yesterday and they suggested I try this prop
https://www.overtons.com/product/details?i=322500
Any thoughts on this suggestion?
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Tue May 22, 2018 1:38 pm
by Soonertoon
Well, it will give you another 1800 revs or should anyway. Depending on the blade profile , cup. etc it may work fine. Only way to know is to try it. I also agree that you need to check the motor position. If shes too low in the water she will struggle as well.
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Tue May 22, 2018 3:58 pm
by Bamaman
Didn't you say you have a two toon boat? Do you have lifting strakes? Is your boat rated for a 150 hp motor?
Most twin toon boats without strakes are 115 hp rated. Due to their being displacement hulls, they can only get up to about 30 mph--and they just won't go much faster. And they are hard to get to the OEM redline. If you do not have lifting strakes, you might want to consider adding them.
My 24 foot Bennington tritoon has a F150 Yamaha and it runs a Reliance 15 pitch prop @ 6000 rpms and 40 mph. A comparable Mercury motor might run an Enertia 14 or 15 pitch prop due to their slightly different lower unit gear ratio.I
Good luck in getting your boat to 100% of its potential.
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Tue May 22, 2018 6:48 pm
by FLOUNDERPOUNDER225
13 pitch with a 150 4 stroke, no way, you’ll lose speed and over rev.
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Tue May 22, 2018 7:11 pm
by andymul87
Bamaman wrote: ↑Tue May 22, 2018 3:58 pm
Didn't you say you have a two toon boat? Do you have lifting strakes? Is your boat rated for a 150 hp motor?
Most twin toon boats without strakes are 115 hp rated. Due to their being displacement hulls, they can only get up to about 30 mph--and they just won't go much faster. And they are hard to get to the OEM redline. If you do not have lifting strakes, you might want to consider adding them.
My 24 foot Bennington tritoon has a F150 Yamaha and it runs a Reliance 15 pitch prop @ 6000 rpms and 40 mph. A comparable Mercury motor might run an Enertia 14 or 15 pitch prop due to their slightly different lower unit gear ratio.I
Good luck in getting your boat to 100% of its potential.
Yes, two toons, no strakes.. It’s rated for a 150. How much performance would strakes add?
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Tue May 22, 2018 7:21 pm
by andymul87
wwind3 wrote: ↑Tue May 22, 2018 2:05 am
Interesting.... the 115 rpm's are low too. What boat are these motors on? A pontoon is a lot like pushing a dumpster thru the water. Is yours a tritoon? If your props are working that hard all the time you will probably spin out your hubs in short order.. Mercs usually run in the high 5000's. My 90 redlines at 5850 approx. Good luck.
Oh--make sure motor isn't set too deep in the water. Cavitation plate should be even with bottom of center mounting pod.
btw--I'm running a 13 x 16 pitch on mine- I had it repitched to 17 and lost about 350 rpm's and some speed-so I switched it back. I am running a 3 blade prop....
Is that too deep? I don’t think it looks like it. It was just installed at a dealership so I assume all is well.
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Wed May 23, 2018 2:54 am
by wwind3
looks OK... Is your boat a 26 foot with couches up front. If so---with only 2 toons instead of 3 you may have trouble getting the nose up when trimming..... if I run my 20 ft 90 trimmed down I lose a lot of rpms also.
--like I said--mine runs 27-28 GPS with a 16 in pitch SS prop at 5800 rpms. Strangely tho'--with a 16 in pitch aluminum prop it will run 28 or 29--which is weird..... Point being--there are a lot of variables at work here
Major point --if you make the prop work too hard like it is doing now--you will probably spin out the hub---esp if you pull skiers or tubes, etc. Watch out for prop slip--rpms go up but speed drops off.
Have enclosed pic of mine trimmed out at 27 GPS--still throws a lot of water- I also have underskinning which smooths the ride and helps speed a little. Getting some pics like this may help you figure out what is going on with your setup. I have the fishing model--so no couches up front. Good luck..
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Wed May 23, 2018 11:48 am
by Soonertoon
andymul87 wrote: ↑Tue May 22, 2018 7:21 pm
wwind3 wrote: ↑Tue May 22, 2018 2:05 am
Interesting.... the 115 rpm's are low too. What boat are these motors on? A pontoon is a lot like pushing a dumpster thru the water. Is yours a tritoon? If your props are working that hard all the time you will probably spin out your hubs in short order.. Mercs usually run in the high 5000's. My 90 redlines at 5850 approx. Good luck.
Oh--make sure motor isn't set too deep in the water. Cavitation plate should be even with bottom of center mounting pod.
btw--I'm running a 13 x 16 pitch on mine- I had it repitched to 17 and lost about 350 rpm's and some speed-so I switched it back. I am running a 3 blade prop....
Is that too deep? I don’t think it looks like it. It was just installed at a dealership so I assume all is well.
Id go up a hole. Had to do that on my boat. Made a lot of difference . If too high, drop back down. Takes 15 min to do.
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Thu May 24, 2018 7:36 am
by andymul87
wwind3 wrote: ↑Wed May 23, 2018 2:54 am
looks OK... Is your boat a 26 foot with couches up front. If so---with only 2 toons instead of 3 you may have trouble getting the nose up when trimming..... if I run my 20 ft 90 trimmed down I lose a lot of rpms also.
--like I said--mine runs 27-28 GPS with a 16 in pitch SS prop at 5800 rpms. Strangely tho'--with a 16 in pitch aluminum prop it will run 28 or 29--which is weird..... Point being--there are a lot of variables at work here
Major point --if you make the prop work too hard like it is doing now--you will probably spin out the hub---esp if you pull skiers or tubes, etc. Watch out for prop slip--rpms go up but speed drops off.
Have enclosed pic of mine trimmed out at 27 GPS--still throws a lot of water- I also have underskinning which smooths the ride and helps speed a little. Getting some pics like this may help you figure out what is going on with your setup. I have the fishing model--so no couches up front. Good luck..
13P prop is delivering today, so I'll be able to test her out this weekend. Not sure if I'll be able to get pics or not on the water. We'll see.
Here's they layout, couches don't make it all the way up, but the pair of captains chairs aren't light either.
I've never noticed much difference in performance while trimming. Maybe I've had the wrong prop all along even with the 115.
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Sat May 26, 2018 7:01 pm
by andymul87
UPDATE!!
Took her out in the river today with a full tank of gas, two people (including myself), and the new 15.6” 13P SS prop. WOT topped out at 5400 RPM trimmed up a bit with a top speed downstream of 30mph and 25ish upstream.
Next step I guess is to raise it up a hole, right?
Any other thoughts?
Re: Need Help - Only getting 4100 RPM @ WOT
Posted: Sat May 26, 2018 8:14 pm
by Rick McC.
^^^^ The pic you posted looks like it’s set up OK to me...