Motor experts, need help setting up

[willyworm]

I finally got the Nissan 40 3 cyl. on my new-to-me 16' Xpress. I'm ordering a tiny tach and will be playing with props to find the right fit, cause the one that came on it is simply not gonna cut it. But as far as setting the motor, should I raise it a notch? I think I read where D's Tees said the cavitation plate should even with the bottom of the boat? Look at the pic and tell me what ya"ll think. FYI, the motor has power tilt, and is mounted on a kick-up plate.









Haven't even had the boat on the water yet. Looking to do so soon, although I will probably miss the duck run due to work.

[Redleg Camo]

The height of the motor depends on what prop you're running and a few other variables.
I would start out even with the bottom and hopefully work your way up .

Sent from my galaxy s4 using Tapatalk 2

[willyworm]

Cool, thanks. Trashduck was telling me that depending on the weight and all, a 15 or 16 pitch would push the hull well. Prolly going with stainless.

[LabLuvR]

Looks right to me.

[Redleg Camo]

pretty sure that's a 1.85:1 lower gear. I think you'll be in the 13-14p range. I would try a powertec SCB3 14p to start. order from dansdiscountprops.com. you can exchange for 40.00. SCB will give you more bite when trimmed out. It will also allow you to raise the motor. higher motor = higher speed = higher RPM's.

[willyworm]

D, is there any way to determine for sure the gear ratio other than taking it apart?

[Redleg Camo]

D, is there any way to determine for sure the gear ratio other than taking it apart?

yea, i looked at the user manual online. gear is 13:24 or 1.85:1

[Redleg Camo]

is that a pull start motor? post a pic of the cowl.

[Rubberhead*]

...a 15 or 16 pitch would push the hull well. Prolly going with stainless.

That seems a little too tall. And, if you go SS, you need to drop down 1" of pitch - I'm thinking a 12" SS for that boat.

http://nissanmarine.com/accessories/prop_chart.html

[Redleg Camo]

That seems a little too tall. And, if you go SS, you need to drop down 1" of pitch - I'm thinking a 12" SS for that boat.

http://nissanmarine.com/accessories/prop_chart.html

i'm turning a 13p on my rig with about 35-40hp, same gearing. Being that he has set back and trim, i figured 14 would be a good start but i think that will be at the top of his range. also depends on what type of prop. a turbo hot shot or stiletto triad will turn rpm's, but has to be burried. aint but one way to find out...

[reeltight]

Yes...generally speaking the cavitation plate needs/should be centered with the bottom of the hull. off an inch here or there will only be determined by the pitch of the prop.

[Rubberhead*]

i'm turning a 13p on my rig with about 35-40hp, same gearing. Being that he has set back and trim, i figured 14 would be a good start but i think that will be at the top of his range. also depends on what type of prop. a turbo hot shot or stiletto triad will turn rpm's, but has to be burried. aint but one way to find out...

I honestly responded to willyworm's post before I read yours. I agree 100% with what you're saying for two reasons 1) you're probably right and 2) you've got way more experience than I do.

You're right about the only one way to do it too. I do prefer to start on the short side simply because the rev limiter will let you know if you're too short. If you get a tall prop and like it, you can never really be sure if a shorter prop will give you a better hole shot with the same top end.

[willyworm]

Sounds like my memory from the conversation with Trashduck is a little fuzzy. I'm sure he wouldn't steer me wrong.

D, it's electric start. It was on a pontoon previously and I converted to a tiller setup but kept the keyed ignition harness for the electric choke and convenience. That saved me from having to rig up a push button start and/or buying a few more parts. I found the tiller handle, bought the bracket for the throttle cables, a shift lever, and a few other odds and ends and viola. Hopefully I'll be on the water this weekend. Unfortunately, it'll be one day late for the duck run.

[willyworm]

I would try a powertec SCB3 14p to start. order from dansdiscountprops.com.

Look like all the Nissan Powertechs start with a N...

[willyworm]

Ok, so I followed D's Tees' advice and order a 14 pitch Powertech prop 3blade. I went out for a short ride and recognized an issue with the throttle cable where I wasn't getting all the way to WOT (keep in mind I converted this motor from a steering setup on a pontoon). I fixed that and took it for another ride. I only got to 26 mph, and when I trim it up to get some more speed the boat starts to bounce. Granted with the boat empty except for motor, gas and me, all the weight is in the back. When I take off I have to bury the motor with the electric trim to get it to plane off then raise it gain some speed once I get there.

Fwiw, I did not get an exact reading on the RPMs. According to the Tiny Tach, I was turning about 4500 at WOT and getting about 25 MPH. According to the owners manual I should be turning 5000 to 5700 at WOT.

Wrong pitch prop? Motor too low maybe? I have the motor mounted at the highest spot without having to drill some new holes in the kick up plate. Motor runs smooth but it feels like it's not giving as much as it can, like maybe there's a carb issue or something. Idles smooth as well.

[Redleg Camo]

you should be close if not dead on with the prop. sounds like you need to focus on the bottom of your boat and motor height. might need a little hook in the bottom and move a little weight up front. the boat is bouncing because you dont have anything holding the nose down. you can do that with hook or weight up front.

[Redleg Camo]

is the cav plate at least level with the bottom?

[willyworm]

I have raised the motor since those original photos were taken. Cav plate sits just above the bottom of the boat.

[willyworm]

Fwiw, I'm not 100% positive the tiny tach is accurate either.

[carolinaboy06]

You ought to be able to hear when it starts red lining. 1000 delta in rpms is noticeable by hearing.

Just for shits and giggles, have you checked the compression on the motor?