Nissan/Tohatsu throttle cam removal/upgrade to 15hp, timing question, w/p questions, dead CDI tip

[Sea Rider]

Depending on the Tohatsu/nissan model, it's a cocktail combination of intake air restriction, cam shape, timing advance & carb sync.

Happy Boating

 

[glassmancanada]

Will make no difference if set at 0 or -3 deg as carb is still working on ralenti/idle, roller is not touching cam at extreme right end portion.
Happy Boating

Actually I took it out at 0 deg and the idle is way too high, had to dial it back to -2 deg to get it off the roller. If you check the pic the roller is acting on the cam @ 0 deg.

 

[glassmancanada]

I'm ordering fuel pump diaphragms now, took that apart and prev owner put silicone on the diaphragm and a piece got stuck in the needle valve opening in the carb. Engine would perform fine until float bowl ran out. Seems like I find and fix one problem then another comes up and so on........

 

[Sea Rider]

Actually I took it out at 0 deg and the idle is way too high, had to dial it back to -2 deg to get it off the roller. If you check the pic the roller is acting on the cam @ 0 deg.

Don't know why you like continuing messing with the whole engine if you haven't swapped 15 cam, right ? Forgot to mention that idle rpm must be slight decreased with carb's idle screw to lower engine's revs to a point that when lever is in forward gear while pushing combo engine doesn't die from low idle rpm. Check 15 cam pic, roller won't be even close touching roller at extreme right end of cam. Once cam is swapped probably will need to perform a new timing plate/carb sync.



Buy an indiction tach to set factory rpm while at neutral/foward, maximize prop, know rpm readings at different throttle settings and keep meterd worked hours.

If buying second hands OB's a complete check out must be done from prop to upper cowl to assure all systems works spot-on and not be left stranded in middle of your boating location.

Happy Boating

 

[glassmancanada]

Don't know why you like continuing messing with the whole engine if you haven't swapped 15 cam, right ?
Happy Boating

Because as I suspected I have fueling issues that need to be sorted before putting in the 15 cam. Silicone plugging the needle valve from the patch job on the fuel pump. So I will rebuild the pump and eliminate fuel starvation and then put on the 15 cam.

 

[glassmancanada]

Forgot to mention that idle rpm must be slight decreased with carb's idle screw to lower engine's revs to a point that when lever is in forward gear while pushing combo engine doesn't die from low idle rpm.

Do you mean the air/fuel mix screw or base idle screw?

Once cam is swapped probably will need to perform a new timing plate/carb sync.

Any details on how to perform this? I've got the fuel pump rebuilt and the 15 cam installed

 

[Sea Rider]

-Must turn ralenti idle screw some CCW turns to lover raised rpm if opting setting timing advance to 0 deg. Back it to a point that when engine is geared while pushing combo doesn't die and maintains good slow idle, adjsust as necessary for this not to happen.

- Throttle fully the grip, check if achieving carb's butterfly full stop at 180 deg, If not post a pic of carb's linkage to check that out.

Happy Boating

 

[glassmancanada]

- Throttle fully the grip, check if achieving carb's butterfly full stop at 180 deg, If not post a pic of carb's linkage to check that out.

Happy Boating

Got it on the first part thanks. Did this ^^ when the cam was installed

 

[Sea Rider]

If already there, when at full wot, check that you can turn freely the white roller pressed against cam with your fingers. You don't want an over actuation there as will wear plastic parts faster, worst if liking going full grip constantly.

Happy Boating