Question about new motor

[beamishken]

Originally Posted by Pikey Dave

Is this going to be the issue though? If you're hitting 5500rpm, you're only 200 short of hitting the limiter, another 200rpm isn't going to get you the extra speed you're looking for.

It's not going to fix the problem but it's the first step, Assuming once the throttle is fixed the engine then hits the rev limiter because it's under propped he can start increasing the pitch until he gets the rpm back down to just under 5500rpm

[jeffstevens763@g]

dave is the linkage limited out of gear?

he's reaching 5200 rpm now at 32 mph with a 13 x 16 .3 ? prop. in post 6 the guy is getting 39 mph on a 13 x 19 at 5200 rpm same as he was getting with his 90.
could he possibly be running a 23 inch pitch or larger diameter.

just thoughts

[Pikey Dave]

Originally Posted by beamishken

It's not going to fix the problem but it's the first step, Assuming once the throttle is fixed the engine then hits the rev limiter because it's under propped he can start increasing the pitch until he gets the rpm back down to just under 5500rpm

Fair point[emoji106]

[Nos4r2]

I've just looked at the wiring diagramme for both motors.

Both the V4 115 and the 90hp IL3 run the revcounter from a separate 'lighting coil' that's not part of the charging circuit.

It's a green wire all the way back from the tacho to the flywheel.

The plot thickens.

[Nos4r2]

Wiring diagrammes attached.

Note that there's quite a few different diagrammes, but they all have the lighting coil connected to the tacho.

[office888]

Ideal prop should be 13x17 or 13x19

Max speed should be between 38 to 48 mph or so.

Sounds like a combination of a motor issue with not enough trim? If your outboard is on hole #2, you'll probably have to trim up 60-70% on the gauge to achieve maximum speed.

[Blue Man]

Thanks everyone for the replies. I'd like to resolve the throttle/carb issue before I evaluate anything else as that seems like the most obvious problem. Does anyone have any suggestions on why the carb butterflies would open all the way in reverse full throttle but not in forward?

Obviously, the cable goes in the same direction (pushes out from the controls) regardless of whether the controls are in forward gear or reverse gear. Why the difference in movement?

[beamishken]

Sensible approach re sorting the throttle first
I think I'd take a look at the helm end and be sure the cable is located in the correct position some helm units have various positions for cable location for different applications and it's possible it is set up incorrectly
The 90 may have tolerated a shorter throttle stroke where the 115 won't

[Blue Man]

I'll look for a web-based user manual.

Originally Posted by beamishken

Sensible approach re sorting the throttle first
I think I'd take a look at the helm end and be sure the cable is located in the correct position some helm units have various positions for cable location for different applications and it's possible it is set up incorrectly
The 90 may have tolerated a shorter throttle stroke where the 115 won't

[Davie]

The 75/80/85/90/115 all run 12 pole tacho so the gauge should be correct.

[cgoing]

Sounds like you will need to adjust cables which may bring you way up over max rpm then prop accordingly to get back in the range. The combination of the two SHOULD help your performance. I have a Nautica 18 with a Yamaha 4 stroke in my shop for retubing. I can check what it has fit a prop if you'd like.

[Blue Man]

That would be great Cgoing! Thanks

[cgoing]

13 x 19 aluminum on this one

[Blue Man]

Thanks for checking cgoing!

[cgoing]

No problem

[beerbelly]

iv a 130hp v4 yam 2 stroke on my rib hits 40 knots on billiard table flat water if I trim it right anything I can check on mine to help I think there basically the same motor as the 115

[Blue Man]

OK, so I figured out the problem. First I had previously reversed the forward/reverse and flipped my Yamaha 704 binnacle control to give me a few extra inches away from the steering wheel. The old motor had less range of motion in the throttle so I never had a problem, but the new motor has more range of motion. The original controls are set up to not allow you to go full throttle in reverse. Since I reversed the throttle control and it wasn't an issue on the old motor, I didn't know the limiter in the remote throttle control existed.

The fix was a simple as reversing two external screws in the exterior of the Yamaha 704 controls and I now have full throttle in forward gear and partial throttle in reverse. Thanks everyone for your assistance.