Performance in salt vs. fresh water, a conundrum!

[jergofish]

I picked up my 215 with a Suzuki 175 from my dealer the end of May. I was able to get about 28 hours on the engine before heading down to Mexico for a month and a half. Running on California gas with ethanol in fresh water I was able to run at 5900 and close to 45mph.

Then we went to Mexico. The engine ran really rough and acted if it was running very rich when it was warming up. Pemex pumps pure gasoline, not gasohol. In the salt I was only able to get to 5400 and about 38 mph. There were some other differences in humidity (20% higher) and water temperature (10 degrees higher). I was worried since I had just had my 20 hour check up and I was afraid that the dealer had screwed it up. My mileage was off as well. Where I was able to run 3400 rpm @ 5 gph in NorCal, I was running 6 gph @ 3400 rpm in Mexico

I'm now back in NorCal and just added 23 gallons of gasohol, mixing it with the 15 gallons of Mexican Pemex still in the tank. I can see my performance figures rising again. I was able to run 5800 rpm and got close to 40 mph. My gph have dropped as well. I expect that when I completely purge the Mexican gasoline from the system my numbers will match those of before I left.

Now it seems that all of this is backwards! I would think that in denser saltwater, I would float higher and the prop would have more to push against, therefore I should have been able to go faster, not slower. The increased humidity would have allowed for more water vapor, causing greater combustion force as well.

As to the gasoline vs. gasohol, I would also think that the gasoline would outperform the gasohol but again, the facts seem to point to the opposite.

Does anyone have a clue why the numbers change for fresh and salt and why the opposite of what might be expected occurs?

[blakinsmith]

Jergofish........I've done quite a bit of fishing around Loreto - Catalina, Monserate Islands, etc - and had my 210 down there in March. Perhaps it was the hot mexican sun, cervezas, and other-worldly experience of spending an extended time in Baja which make your recollection a bit fuzzy?!?!?!

Just kidding. I don't have a clue - next time I go I will check my perf #s. My only real thoughts are perhaps you had the boat loaded a bit more - fish, ice, people, gas, or trimmed a little different due to seas or wind, or maybe you've had some water seep into some of the inner hull foam and add weight.

Sound like you are enjoying your boat........good luck in your detective work......"Bite Me" Barry