new nissan 5hp fourstroke---rejet? PLEASE HELP!

[porta-homer]

Hello-<br />I am new to the board, and brand new to motors. I have a 12' folding porta-bote and bought a 2004 nissan 5hp 4 stroke for it in January, they shipped it to me here in Utah, straight from the factory in Texas. The first time I took it out it would kill whenever I put the throttle to the slowest speed. The closest nissan dealer is 80 miles away, so I took it to our local mercury dealer and he adjusted the idle speed to match the elevation of 4500 ft. I also called the nissan factory, and they were very helpfull and said that I needed to rejet the carb. to match the elevation also. The mercury dealer told me he he wasn't allowed to do this because of emissions rescrictions he is under. I took it out again yesterday to continue the break-in, and put it up to full throtle and was surprised at the lack of power. There was no difference in the power between 3/4 throttle and full throttle. Our boat weighs 100lbs and there was about 400 lbs of people/gear and the fastest we could go was a little over 8mp, not even on a plane. So, what should I do? Call nissan and see if they can send me a rejet kit; will that solve the problem? How can I find out how to rejet it myself? Is it bad to run the motor without rejeting it? Thanks in advance, any advice is much appreciated!

 

[clanton]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

Call Nissan, they should have a chart that tell you jet size for elevation, and have the Jets. If not file a complaint with the EPA.

 

[DJ]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

Rejetting will help with the runability, but it will not turn it into a speedster.<br /><br />Any four stroke (non turbcharged or supercharged) engine is going to lose a lot of its potential at 4500 feet.

 

[porta-homer]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

Thanks!<br />So are the jets the reason it runs the same speed at 3/4 throttle as it does at full throttle? Will re-jetting fix that problem?

 

[clanton]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

It will help.

 

[DJ]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

porta-homer,<br /><br />Yes, it's just running out of breath. Not unlike me at 4500 feet.

 

[porta-homer]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

Well, I called my closest nissan dealer to order a rejet kit and he said that rejetting it wouldn't help and he thought it needed a smaller lower pitch prop. Now I am really confused!

 

[LubeDude]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

4 strokes arnt as suceptable to elevation changes as 2 cycles are, however they are effected. You actually need smaller jets, the next size down should be Ok. Also the prop pitch needs to be changed also. Difficult to tell what pitch though when you do not know the RPM you are currently running.

 

[porta-homer]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

Took the boat out again today and hooked ut a tach. The motor is only getting 2500 rpm at full throttle with just me in the boat, which was 11mph and barely on a plane. When two are in the boat we got 2230 rpm, 8mph and no plane. Nissan factory said I didn't need to rejet, but needed a lower pitch prop. I am at an 8 right now, will lower pitch get me to 5500 rpm?

 

[T S N]

Re: new nissan 5hp fourstroke---rejet? PLEASE HELP!

I just tested a porta-bote last week.<br />It was a 12 foot about 2 years old<br />I tested with a 5 hp honda 4 stroke.<br />Top speed, at sea level,with 3 gallons of fuel,me at 195 lb and boat only reach 13.5 gps mph.<br />I noticed the transome would flex some and push the front of the boat down,maybe causing some speed loss.<br />My top speed with wife in the boat with me was 8.5 or so.<br />I dont know if this info will help you, but I thought you might like to hear of another persons experience with porta-bote.