Question for Elvin;

[Salmon Tub]

Hi Elvin, I was wondering, when a shop is tuning a motor, do they use the OEM tach (dash gauge) or for accuracy purposes is it prefered to use one that either picks up electrical pulses (proximity) or one that uses a reflective sticker? I have a Nissan 90A and would like to use as accuarate a tach as possible for tuning. Any info is greatly appreciated. Thanks!

 

[TOHATSU GURU]

Re: Question for Elvin;

It really depends on the tech, dealership and engine model. As the average mechanic is much more concerned with getting done as quickly as possible rather than a more accurate reading from something they have to hook up.....Unless there is a reason to suspect the OEM tach, we have always used the factory guages. Are you setting the idle and concerned that you are too high or too low? Or, are you propping for WOT?

 

[Salmon Tub]

Re: Question for Elvin;

The situation is the following: The sticker on the side of the engine says: Idle 900rpm out of gear, and in gear idle: 750 or 700 rpm (I don't remeber). I have found that the engine is happiest at 800/600 rpm (out of gear/in gear) per the OEM gauge. If I raise it to 700+ in gear, then when I put her in idle, it goes up to about 1000 rpm (too high). Even setting it at 900 rpm per OEM gauge when out of gear seems high because it shifts hard at that speed and the tach drops down to just a hair above 600. If the gauge is off and shows less by say 100 rpm, then the 800/600 is about right. at 800/600 rpm, when flushing with earmuffs on land, the engine idles at about 1000-1100 rpm, I imagine the increase is due to lack of any exhaust backpressure. If the tach is correct, then I do not know what it could be as it is impossible to achieve the speeds on the sticker. BTW, I used to have a Tohatsu 40D on this boat. When I repowered, I used the Tohatsu gauges for a while, then after a year replaced all gauges and harness with the ones supplied with the 90A. The swap did not resolve the situation. How arbitrary are those speeds on the sticker, are they rock solid or for reference only. The timing is set at 5 ATDC at closed throttle as per sticker/book and carbs are synced and pilot screws adjusted. <br /><br />Also, being that this engine uses a CD Unit, is it true that they need at least 600 rpm to operate and give proper spark? <br /><br />Normally it would not matter so much, but I do alot of trolling at idle, and want to make sure that the engine is properly tuned for that speed. Thanks in advance for your help!

 

[TOHATSU GURU]

Re: Question for Elvin;

I'll look it up and post the specs in the morning. I remember it as 650 in gear....I think. With age, the engine may require a small increase in RPM. The trigger coils under the flywheel require at least 600 to maintain apulse to the CD. Basically though, just set the thing to 650ish and change out the plugs every 50 hours(idleing really loads them up). Burn one brand of oil only, dosen't matter too much what brand. I like Yamalube. Just remember that when you shift.....snap it in and out of gear.....do not gently put it in and out gear.

 

[TOHATSU GURU]

Re: Question for Elvin;

It is 550-750 in gear according to the specs. As you said it works well at 600, leave it there are maybe come up to 650. Your guage probably reads a little low. I spoke with the National Service Manager at Nissan/Tohatsu and he said 650-700 was where he would put it. But again, you don't screw with something that works.