130 Johnson can't get over 5K RPM

[bowhunter71]

I have a 1995 Johnson 130 25 shaft that I bought used a few months ago.I mounted it on a Polar Kraft 2096XCC aluminum mod V boat that I am guessing weighs around 2300 lbs as it sits including the outboard.It runs great but I can not get it to go past 5K rpms.I have tried 3 different prop sizes and with all 3 it won't go past 5000 rpms.I do know that the lower is not the original it has a lower from a V6.So I know the gear ratio is off.It came with a 15X17 SS that will make it run about 5000 rpms at 39 MPH(GPS).I tried a aluminum 14.5X19 and it ran about 4300 rpms at 33mph (I think.I did not write it down).After trying the 19 pitch prop I raised the motor as high as I could with the factory mounting holes.Then I tried a aluminum 15.5X15 and got 5000 rpms at about 38 mph.I also tried a SS 15.5X14 and got 5000 rpms at about 35 mph.The tach is a brand new faria.I was wondering can I adjust the throttle stop a little to see if it helps or do you guys suggest something else.If you need more info let me know.
Thanks,Jeff

 

[muchco]

Re: 130 Johnson can't get over 5K RPM

Hi, it appears you may have an issue with your tach. Information I have shows that the stock gear ratio on your engine is 2.25:1. When you say that you know the gear case is not original and from a V6 do you know what it came off of? The 130 V4's do have the larger V6 style gear case with different gearing, most V6's are geared at 1.86:1. Below are the factory specs for your engine.

Motor Specs
Manufacturer: Johnson
Year: 1995
Horsepower: 130.0
Cylinders: 4
Type: 2 stroke
Gear Ratio: 2.25:1
Min WOT RPM: 5000
Max WOT RPM: 6000
Spline Count: 15

This being the case, if with the 17P prop your are running 39 mph (gps) this we know is correct, let's look at the two gearing scenario's.

(5000rpm/1.86*17*60)/5280/12= 43.3mph theoretical 39/43.3= 10% slip

(5000rpm/2.25*17*60)/5280/12= 35.7mph theoretical 39/35.7= -9% slip (not possible)

The key would be to figure out your gearing as negative slip is impossible and if you truly have V6 gearing at 1.86 with the 130 you are going to have to prop down to get the RPM up as the V4 is geared pretty tall with the 1.86 gears.

To check the gearing take the plugs out, put the engine in gear and turn the fly wheel by hand one complete reveloution and record the reveloutions of the prop. To accuratley diagnois your problem we need to know the correct gearing. If you have stock gearing I would suspect you have a tach issue and if you indeed have V6 gearing of 1.86:1 you will definetly have to prop down to get the RPM up. It also wouldn't hurt to check the compression on your engine to see if it's up to snuff. One other thing to keep in mind is that your Polar Craft most likely has a 20" transom and with the 25" leg you are not going to have a very efficent set up pending how the engine was mounted. 5" of drag you don't require if the engine is sitting right down on the transom.
I hope this helps let us know what you find out.

 

[bowhunter71]

Re: 130 Johnson can't get over 5K RPM

Thanks for the reply muchco.I wonder why my post was moved.I am not asking about props I was using them to show an example.I thought it was more of a throttle or carb adjustment.Anyhow I already checked the ratio it is 14:26.It should be 12:27.My boat has a 25" transom I wish it was a 20" would have been easier to find a used outboard around my area.My engine has just over 130 pounds of compression across all 4 cylinders.I was just thinking that maybe the engine was not adjusted to reach enough RPMs because with a 14 pitch it should have no problem reaching the max RPM.I will have to try to find another tach to make sure mine is working right.I don't think the engine sounds any different with the 14 pitch than it does with 17 pitch at full throttle.Again thanks for the reply.If you have any more ideas throw them at me.
Thanks,Jeff

 

[Dhadley]

Re: 130 Johnson can't get over 5K RPM

You're headed in the right direction. Verify the tach, make sure it's set on position 6 and check the sync-n-link to make sure the motor is doing all it can. Also make sure it's running on all 4 at or near wide open.

 

[bowhunter71]

Re: 130 Johnson can't get over 5K RPM

Dhadley I have the tach set on number 5 that is the highest setting.According to faria's web site that is where it should be set for a 12 pole charging system which there chart shows it as a 12 pole.Does that sound right?
Thanks,Jeff

 

[muchco]

Re: 130 Johnson can't get over 5K RPM

Bowhunter71, I believe that you are correct with the Faria's #5 tack setting as I see the same thing you do. Just a thought is that stock gearing for a 130 is 2.25 and you have speeded up the gearing by 20% to 1:86. I have seen alot of 130's like yours installed on similar applications in the stock mounting configuration and they have there butts full pulling a good 19 pitch prop. If you were to take the gearing change into account taking 20% of a 19 pitch puts you in that 15 pitch area. Would it be possible to post a picture of your boat and the way the engine is mounted. It would also be advisable to verify the tach reading. You motor appears to be healthy, and the link and sync won't hurt.

 

[hwsiii]

Re: 130 Johnson can't get over 5K RPM

Hunter, after running some numbers on your boat I am kind of at a loss for words a little bit. You definitely have a Tach that is not working correctly . It does not show an RPM increase from a 17" prop to a 14" prop. Theoretically it could be the motor possibly not opening the throttle all the way or other reasons. But that is why running the numbers matters some of the time when looking for problems. The following numbers prove it is the Tach because the tach shows them all at 5,000 RPM and yet the last two, the 15" and the 14" show a prop slip of 0% and 2% prop slip and that is impossible to have those speeds at 5,000 RPM. Your tach is just not showing the true RPM above 5,000.

Prop Slip

H

 

[Dhadley]

Re: 130 Johnson can't get over 5K RPM

I've never been a fan of the Faria tachs but unfortunately with T-flex getting out of the gauge business a lot of distributors are turning to Faria. We're probably going to see a lot of these issues in the future.

If you're sure the motor is running properly then I'd verify the tach. If the tach and motor are correct then look at pitch. But only after verifying the tach & motor.