Repower Project:
New Wheels for Toy Boat 2

We decide to put a new motor on our project boat. Read about what went into the selection, and initial impressions on our new motor.

Toy Boat 2 with her new E-TEC 90 hit the water on December 12, 2005. We stayed inside San Diego bay for the most part to do some speed/fuel comsumption testing, then ran out to the 9 Mile Bank and Point Loma. Mostly, we were very impressed. Here are the results:

Test Conditions:

Weather: Air temp - low-mid 60s, light SE breeze less than 10 knots Water conditions: In bay - flat, strong outgoing tide Outside - small swell, light wind chop

Performance:

Recall that the motor was a direct swap for a carbureted 1991 Johnson V-4 90 HP 2-stroke that was in good condition. We were not expecting to see any significant change in speed, holeshot, etc., and that was the case. WOT RPM under full load was the same (5000 RPM with a 13.75 x 15" prop), top speed was right around 30 mph. We were using a Piranha composite prop, so we swapped the 13.75 x 15" blades out for 14 x 13" blades, which allowed the motor to spin up to the maximum Manufacturer's WOT setting (5,500 RPM). Holeshot improved noticeably, and max speed remained the same, so testing was done with this prop.

Click HERE for a Speed vs. RPM chart

Fuel Economy/Mileage:

Our fuel mileage went way up. Fully loaded, TB2 used to average 2.9 MPG at cruising speed. On Sunday, with a fully loaded hull, we averaged 4.1 MPG (41% increase ). We ran some fuel consumption tests at different RPM settings, and with a moderately loaded boat, TB2 achieved 4.9 MPG at cruising speed. Our previous best was 3.1 MPG (58% increase ).This is without significant trim adjustment, so we should be able to break 5 MPG after the motor loosens up a bit, and we have a better handle on trim. At trolling speeds, the mileage increase was huge. We recorded mileage as high as 15.6 MPG @ 3.9 mph to around 3 mpg @ 9 mph. This last value is slightly below planing speeds for TB2, and with the old motor, we were only getting 1.5 mpg @ 9 mph (a 100% increase )

Click HERE for a Fuel Burn vs. RPM chart

Click HERE for a MPG vs. RPM chart

Emissions / Oil Burn:

• We went 56 miles total miles on the first day. Checking the oil tank at the end of the day, it looked like the oil level was down about 1/3. But it is an odd-shaped tank (looks much skinnier at the top of the tank) and, we're embarassed to admit, we didn't know for sure that it was full when we started (doh!). The tank is 3 quarts, a rough estimate would indicate that the engine was running at an oil:gas ratio of something better than 1:80 .
  
  
• Our understanding is that the engine computer bumps up the oil:gas ratio during the first 50 hours, so oil consumption should get better with time .
  
  
• We did see some light white smoke after running the boat under load at higher RPMs, but when we shut off the motor, then restarted, it went away. We believe that the engine computer was adding some extra oil during these first hours when we were running for extended periods at higher RPM.

Sound/Noise:

• The motor is much quieter than our old carbureted 2-stroke. Not silent, but quiet.  We spoke to someone at the docks who thought it was a 4-stroke because of the low noise level and lack of smoke.
  
  
• At WOT the engine is quieter than before, but seems a little louder than 4-stroke motors that we have observed .
  
  
• The engine definitely has a different sound to it - a much lower frequency. Unfortunately, at idle, this actually caused some sort of harmonic in the hull, and we could hear something rattling. As soon as we increased throttle, it went away. So we've got a little investigation work to do.

Other Notes:

• The claimed "instant starting" is true. It always started on the first turn of the key, even cold.
  
  

So that’s about. Stay tuned to the Toy Boat 2 Scorecard for an ongoing report on performance and any issues!

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