Help on set 91 Champion 186 DC Yamaha 175

Hey guys I am trying to help my brother out with setting up his boat that I just sold him. It had a 150 Yamaha on it and I ran it for 12 years and never changed a thing as it was previously Brent Chapman's boat. The 150 I had spun a bearing and we picked up a 175 Yamaha from reputable Yamaha rebuilder and we are going through the break in process and it won't get above 5300 rpms. My old 150 would turn 5700 to 5800 and before it gave out it was closer to 5400. I can tell you that the Yamaha 23m prop that is on it was beat up a little so I suspect that is the cause for the drop in rpms. Since I am pretty sure the motor is fine I want to start with the other items to begin to eliminate possibilities so he does not spend a bunch or time or money. My first question is what is the recommended pad vs. prop measurement, it has a 4" jackplate. Additional questions I have is what prop should be on this boat and what speeds are you guys getting? I think best I have seen is lower to mid 50's with either motor....given that we were only recently able to get an accurate reading on the speed. Thanks for your help!

Re checked the pad as the boat was not level when originally checked. It is at 4.25. This seems like a bit much and not sure this will give me the extra 500 rpms. Any help guys?

Bring her up to 3.5 below and see if that helps...but it does sound like you need a better prop!

Interesting...I was not aware that Brent Chapman had ever run a Champion. Cool!

We will get it moved to 3.5 and I think we just found a 23m that we can borrow so hopefully that will do the trick. I will report back once I have some more information. Brent had the boat 20+ years ago, rigged by Smithville marine, and I was the 3 owner as the 2nd didn't keep the boat very long. It has served me well for many years and I hated to give it up but I wanted something a little newer and hey it is staying in the family. Thanks for the help!

Hey guys I am trying to resolve an issue with a mid 90's 175 Yamaha that I am running on a 91 186 DC champion. The issue we are having is the motor has been rebuilt by a reputable rebuilder although they took a few different components to build this particular motor (i.e. Lu, intake, carbs, heads). I feel confident that they know what they are doing but we are not hitting the right RPS and we are trying to troubleshoot the issue. We are not getting the right RPM's at WOT, around 5200-5300, with a 23M Yamaha prop. The rebuilder originally wanted to drop the prop down in size but we would have to run a 20P and that doesn't seem right. They are thinking that we could try gears from my old 150 which are 2.02 vs. the 1.86 that I think all the 175 hp motors come with. Just curious if anyone with a similar setup as far as the hull and motor knows any information for the following for your set:

• Lower unit gear ratio
• Prop
• WOT rpm
• WOT speed .

Thanks in advance if you are able to help out.

Also I did get the prop to pad adjustment to 3.5 with not much of a change.

I imagine that perhaps Brent may have been on smithvilles pro staff before he went pro or perhaps he just had a champ as a federation guy. Smithville marine was a champ dealer for a few yrs. I purchased a new 181 through them back in 96. Good folks to deal with then and I'm sure they still are.

Don't know if this will help or not. I had a 1991 - 184 DC Super Champ with a 1990 150 H.P. Mariner Mag II. Motor was bolted directly to hull on the 3rd. hole. With a 22 pitch Predator prop, it turned 5,800 rpm and ran 66.2 mph (GPS).

Thought I knew how to run a boat until his one. Once I learned to drive with the chine walking, it was the best handling and setup boat I ever owned. Sure do miss it. I've moved on and 3 boats later I'm back to a Champ. 2000 - 223 DC-Elite. What a ride.

I did a motor swap on my 186 and my very reputable mechanic didn't recheck the throttle for full advancement at WOT. I was missing almost 25% of my throttle advancement. You might double check that. My motor is an Optimax but also has 1:86 gears and the 23" prop is great. My jack plate is 5.5" and I run 4" below pad for better water pressure. Water pressure was marginal (12 PSI) at WOT at 3 1/2" and I prefer the security to the top end speed.

For what its worth I have a 20p on my 184 with a 175 Mariner. Great holeshot and RPM's get up over 6k if you let it. I am looking to move to a bigger prop to keep the RPM's down.

As said check your throttle first. Not getting WFO is more common than you think.

Also different gear ratio on the 175 so that makes a difference.

Quote:

---

Originally Posted by pmgoffjr

As said check your throttle first. Not getting WFO is more common than you think.

Also different gear ratio on the 175 so that makes a difference.

---

Thanks guys. They have checked to ensure it is reaching WOT but unfortunately that wasn't it. I saw in the Champion setup page that the 150 on this boat would run a 23m in the second hole and the 175 recommended a 25HD in the 3rd hole. It makes sense that the ratio will make a difference I guess what I am trying to figure out is if the 175 ever came with a 2.02 or only the 1.86. If it only came with 1.86 I would need a 19-20P prop and that doesn't seem right based on most of the similar setups I am seeing. Am I thinking about this wrong?

You should be running a 25M prop at 5,600 rpms at 65 ish mph.

Thanks Pat. That is pretty close to what I think it should be doing but wanted to hear some other opinions and if others have setups that are similar. This will give us more reason to keep looking for the cause as we are not turning the right RPM's with the Yamaha 175 with 1.86 gears and a 23M. If we put the 25 on the current setup the numbers would be closer to 5000.

Can anyone confirm that the 175 should not have or need the 2.02 LU? I suspect that with the 2.02 it should have bigger than a 25p and it can't turn enough RPMs with the 23.

I can not confirm that a 2.6 175 never came out with 2.02 gears in it. I see that the LU was changed are you sure it has 1.86 gears?
I hope you find the issue, I would not settle on changing gears unless you find out that 1.86 is not in your current set up. Something does not add up here.

I am being told they are 1.86 but how can you check to be sure. Is it possible that they are even lower ratio like a 1.75?

The Pro V has the 2:00 gears, non pro V has 1:86
I'd do this:
Find a known good 23 M or Tempest, and go run it at 3 3/4" motor height. It should be 5,600+ rpms if it's not, then you have a motor issue and can stop thinking setup.

Thanks Pat. This is a bit of a hodgepodge motor so we are trying to make sure all the ratios are right so we can point it back to the motor. I may need to check if this is a pro v or not. Were they made the same year as maybe this is a pro v and it needs the 2.00


It it is a weird deal as they are saying it is putting out the right pressure at the prop for a 175 using some sort of hydraulic dyno. To me it sounds like it is not getting to full throttle but that has been physically checked but makes me wonder if there is some sort of air restriction as it has good hole shot and mid range but just doesn't reach top rpms.

Hard to diagnose over the internet, and hydraulic dyno's are a pretty good gauge of output, but not perfect. The dyno would be run at wide open, I'd like to see it run and compare to what it should be producing.

These are the results from the last lake test which was a bit windy thus some good chop/rollers:


1.86 Lower unit - 23M prop - 5300 rpm @ 59 mph
25 tempest prop - 5000 rpm @ 55 mph


2.0:1 Lower - 23M prop - 5700 rpm @ 58.5 mph
25 tempest prop - 5200 rpm @ 57 mph


Can anyone run these through the calculator to see how the numbers compare to others setups? Slip was around 5 I was told with the 23m....does that sound right?