Getting her dialed in

[Hez]

1990 Ranger - 374v
1996 Mariner 175 hp Magnum EFI (OG360900)
5" manual jackplate
Hot Foot
Mercury Tempest 25p prop (older A45 model - lighter weight compared to the Plus)
2 vent plugs



Ok, here's the deal:

When I got the boat she was 5" below pad, but blowing out on the hole shot when going over about 4000 RPMs - especially noticeable with another person and full tank of fuel.

I ordered plugs, and it was suggested that I raise the motor to 3" below pad.

Plugs came in today and I put 1 in and raised the motor to 3.25 below pad then went to the lake to test drive it.

With 1 plug, I still blew out in the hole shot after 4000 RPMs so I put another plug in. 2 plugs did much better.

Top End:
Top speed was about 55 at 5200 RPM. Light chop - 95 degrees

The boat seemed to be slower. Not much slower, and obviously it reacted different to being trimmed. I think before, when I trimmed up at speed - it would give the boat more lift. Now, it didn't seem to lift the boat as good (or as high) at speed - and the ride was rougher.

I think I should lower the motor on the jackplate about an inch (halfway between where it was before) and see how that does. Maybe the 5" below pad is best for this setup?

My water pressure was good - it just doesn't seem to have the lift - which is creating more drag and slowing the hull down.

Any advice or suggestions are welcome.

[turfy49431]

Rpm's are still low. Raise it a quarter inch to 3" like sugguested and try it again
If you go lower with the motor, its going to chine walk like a SOB

[Hez]

Rpm's are still low. Raise it a quarter inch to 3" like sugguested and try it again
If you go lower with the motor, its going to chine walk like a SOB

My RPMs are "low" because of the Hot Foot WOT adjustment. That was going to be the last thing I "fine tuned" after I got my P2P measurement and Prop plugs installed.

Before I raised the motor (5" prop to pad)I was doing about 61 at 5200 RPM...in those same conditions. I did Chine walk a little...but it lifted the boat out of the water and ran faster.

Prop to pad is now at 3" below pad. Just went and made a quick run - still the same. Loss of speed and digs in the water compared to before.

So my question still stands - is it possible that this particular setup performs better with the motor deeper?

Going to raise it back up to 4" and go run it again....maybe fish for a few hours this time. Will update when I return.

[Hez]

Update: 4" below pad - she is running much better . Has better lift like before, top speed is about 60 at 5200 RPM.

Now I will adjust the WOT screw on the hot foot to gain a few more RPM.

Does this his sound about right?

[mdtritn21]

You had the motor too high prop to pad and that's why it was turning the same rpm's but slowing down. Maximum height on that combo would probably be 3 1/2" below pad. From the low rpm's I'd say you need new plugs, your tach checked because it's reading low and if you have not upgraded your fuel system do all the things in this thread. http://www.bbcboards.net/showthread.php?t=22490

[Hez]

You had the motor too high prop to pad and that's why it was turning the same rpm's but slowing down. Maximum height on that combo would probably be 3 1/2" below pad. From the low rpm's I'd say you need new plugs, your tach checked because it's reading low and if you have not upgraded your fuel system do all the things in this thread. http://www.bbcboards.net/showthread.php?t=22490

Yeah, it was definitely too high. I agree with that, but I was just following advice I received here. Just part of the process.

You are right about new plugs, in fact I just went and got some. I've only had the boat 2 months, so it's at least a peace of mind thing.

Probably a good idea also to have the tach checked - it never really crossed my mind that it could be wrong. That will be high in priority on the list of things to do now.

Thanks for the input.

[mdtritn21]

The fuel lines and cleaning the fuel system are just important as the plugs.

[Hez]

The fuel lines and cleaning the fuel system are just important as the plugs.

All pretty new fuel lines. In fact, I just replaced the Fuel Selector switch and cut one of the short hoses between the switch and the tank to see what the inside looked like. It was super clean. Non Ethanol is what most people run in their boats around here and it's what I run in mine.

[mdtritn21]

It's the gray lines from the bulb to the motor that are the main problem. Look at the lettering and see what color it is, red and orange lettering needs to be replaced with line marked with blue or black lettering.