1999 Nissan 8 HP Question

[Species]

Been a long time lurker and enjoyed reading, but finally have a question I want to ask.

I bought a 8HP 1999 Nissan outboard (2 stroke) and a used 12' porta-bote. I took the boat out on the lake and was able to get on plane just fine with me in the boat. When I put 2 more people in the boat I could not get it to plane and the RPMs were low. My engine has a 3 blade 8.5 pitch prop. My question is: would I notice much of a difference if I went to a 7 pitch prop? Would it be too big of a jump to go to a 4 blade 5 pitch prop?

I would like to be able to get the boat on plane with 3 people. The 8 HP motor is already more power than the boat is rated for (the weight is just right though). Do I have unrealistic expectations. Any thoughts you have would be appreciated.

 

[pvanv]

Re: 1999 Nissan 8 HP Question

Will a porta-bote plane with 3 big guys in it? Dunno, but I suppose it should. Small pitch differences make a big difference on small motors, especially when loaded down. 7 pitch would probably be a significant improvement. But check the WOT RPM with a tach. The HT 4-blade 7- and 5-pitch props are intended to push heavy loads, such as sailboats. Might work in your case when fully loaded, but also might over-rev when lightly loaded. The tach will tell you a lot. Perhaps ask this in the prop forum.

 

[Species]

Re: 1999 Nissan 8 HP Question

To help others I thought I would post a follow up....

After some experimentation with a GPS and family members I am fairly certain that you cannot get a porta-bote to plane with more than 1-2 adults despite what the mfg. states. With an 8hp engine (which is over what the mfg suggests) I can get myself on plane very easily with a top speed of about 14-15 MPH (275 pounds of persons, motor, and gear). Planing speed for the boat appears to be about 11 MPH as evidenced by the floor "sucking" down as the boat transition to a plane. Under a "full load" I am able to get about 10-11 MPH with about 600 pounds of persons, motor, and gear. I can get on plane with myself and one of my kids, but with me and my wife it just doesn't get there. Top speed seems to stay at around 10 MPH regardless of the additional weight I add above just me and my gear.

If you are looking for a boat that is fast the porta-bote is not it. But is is extremely stable, performs very well in rough water, folds up flat and lays up against the wall next to my car in the garage. Also, I put about 400 miles on the road with the porta-bote on top of my Honda Pilot and did not notice any drop in MPG. There are some real advantages to the boat - planing and speed are not among them.

As for the prop - I purchased both a 7 pitch prop and a 5 pitch (4 blade) prop and found the 7 pitch was a significant improvement and actually got me to the RPM's I needed. I ended up not even taking the 5 pitch out of the box. The change from 8.5 to 7 pitch was about 1,000 RPM's for this engine boat combo.