New to this site but have had mudboats for several years.

Not sure if this has been covered much, but how much does weather impact your motor's performance? Lot of talk of speed on here, but never noticed others talk about season, temperature, or humidity when taking speed.

Background details:
I bought a new boat and engine last year after I took the time to figure out which rigs was best for me. I bought a 18x54 PD SBX with 36 hp EFI. Love the boat and motor. When loaded down with 3 people, two large ice chest for fish/drinks, bait tank, fishing gear, trolling motor, 2 bows, 2000 Honda genny, and 8 HPS 150 watt bow lights with rail. When load down, I could only go 17-18 mph. I expected more, but figured I overloaded it, in the hot, humid, summertime south Louisiana marsh. Figured I needed engine mods for heavy load.

Then in the winter with about the same load ( 3 guys with built in low profile blind with popup roof, guns, decoys, heaters etc), the boat did way over expectation. In the river it ran 24-26 mph in both directions of river. Great for a loaded fully decked out blind boat. My old boat would have been about 18-20 mph.

I never thought temperature and humidity would have that big of impact. Maybe the EFI is more sensitive to humidity or temp.

Anybody else see this amount of difference?

Temperature for sure has a big impact, air is thinner in cooler temps so the engine can breathe more of it. So to stay stoich it needs more fuel, and more air and fuel you get more power. Whether it is that noticeable on the water, I have no idea

your pushing a pretty big load - did you go with the PD E2 or just EFI?

My 35GTR with just PD EFI seemed to run about the same, reguardless of weather conditions

Google makes me feel like an idiot, I dont know where I got my theory from ha

New cam you say? This thread just got good....

What compression gauge are you using?
A nice Snap-On vs Harbor Freight Gauge can produce very different results. The important thing is that each cylinder is within 10% of each other. Also, on a 4-stroke a leak down test is much more beneficial for determining engine health over a compression test.

In regards to your speed differences in warm/humid temps vs cold temps.
I don't know anything about how the PD EFI system works, but the only thing I could see cuasing that big of a difference in performance is an overly rich condition in the warm weather. It could be in the base map or in a temperature compensation table within the ECM. If you get too rich you'll be getting an inefficient burn, won't allow it to rev out clean, etc. Maybe the colder temps are bringing your AFR back into a more acceptable range where it is producing good power.

Could someone please enlighten me on how cold thick oil would give differing compression test results?

A leak down test at different engine temps would indicate different things leaking if there's a suspected problem but unless that cold thick oil somehow ends up on top of the Pistons, I don't know how it would give you a higher compression reading. If anything, a cold engine will show less on a basic static compression test due to the pistons and rings being physically smaller and not sealing as well. The same engine would show slightly higher numbers after it's been ran and brought up to temp. I still fail to see what the oil temp and viscosity have to do with compression test readings.

DP...

welcome aboard!

viewtopic.php?f=7&t=59661

You sound awful upset about it I didn't intend to hurt your feelings as it has appeared I have... The last part of that post wasn't entirely directed at you as you have taken it. It's more of an observation over several different forums I'm a part of spanning several hobbies. A few of which involve different types of engines etc... Nice colors too. Nice touch.

The question has already been answered and it really has very little to do with what type of fuel delivery system you choose, or the fuel itself for that matter. It's all about air density, and available oxygen in a certain volume of air. A little investigation on Google would tell you all you needed to know on the subject. I never claimed to be an expert of anything. I get shit wrong every day just like anybody else. I was only validating my response with the fact that I do have practical experience with what I stated and I wasn't speaking from my rectum...

oh, and most definitely welcome to the site!!!!!! If you have a hard time with that response, you're going to have a fairly rough stay most likely. Not a lot of guys known to pull many punches around this place.

I'm still thinking it's not the standard minor changes from air density . I don't know all the sensors used to optimize the efi, but I believe it has exhaust temp sensor... I assume it uses others like a car efi...mass air flow meter? Which could be adjusted or calibrated with an inlet air temperature sensor. I haven't torn into it yet to screw it up.

I don't know, but suspect it's a sensor issue, or program issue.

Runs great in winter, kinda dogs in summer. Very big difference in performance. Since nobody else has the same issue, I suspect I have a calibration issue.

I'll have KP guys look at it when I get an e2 kit installed.

Could the issues be with load placement in the boat more than temperature/humidity differences? Just something else that will have a big effect on performance and speed. Kinda surprised no one else has brought that up.

A properly running engine in summer vs winter temps would absolutely not have that much of an effect on performance. I believe you are correct in the fact that there is an issue somewhere within the calibration or a sensor.

Does Pro-Drive run a closed-loop fuel system?
Typically there are compensations built into the calibration for temps. This would include engine temp, Intake Air Temp & possibly oil temps. Most sensors use a 5 volt reference to give the ECM feedback. A faulty ground wire somewhere could be causing the sensor to peg either high or low voltage, which in turn would be at the far range of the compensation tables for that sensor.

Say intake air temp map is from 0-120 degrees. Zero being a + 20% fuel increase, 120 being a -20% fuel increase. Sensor is defaulting to a "zero degree" reading, adding 20% fuel.

In the winter if you're running 40 degree air temp your compensation is not far off. In the summer if you're running 100 degree air temp, you compensation will be off by 30% or more to the rich side.

Just a possible example of what could be causing that great of a change. Have PD hook up to it and see what's going on.