1994 115 Johnson operating temp, thermostat id, tacho operation

just curious of what operating temp this motor should run at, what temp should the thermostats being opening at. I want to test the thermostats, the current thermostats have 143 stamped on the bottom of them.
Finally I replaced the reg/rect as the tach was intermittent, after R&R of reg/rect tach is now smooth and constant but at about 5600 to 5700 drops out. That is I mean the needle drops to zero as if theres no signal... strange.
I have an OMC manual for the motor but it does not mention thermostat temp, but it does mention the power pack haveing a built in feature that limited revving to 5800 to guard against wrong prop fitted, bad cavitation, unusuall light boat loads. I wonder if this is whats going on. The motor seems to rev past past 5800 but very rarely would I let it get there as factory max rpm is 5500

thanks to all who respond with ideas on these questions

Dean Cameron

Re: 1994 115 Johnson operating temp, thermostat id, tacho operation

Your temp should be 140-150 degrees. Easy way to check is to get an IR Temperature gun. Harbor Freight has them for cheap.

When the tach drops to zero, is the motor dropping as well? Reg/rect is a common tach problem, maybe you have a loose connection somewhere.

Re: 1994 115 Johnson operating temp, thermostat id, tacho operation

The recommended operating range for that engine is between 4500 and 5500. Best to stay at the very top end of that range, or 5500-5700 for optimum perf and fuel economy. The power pack will limit spark beyond 5800, but that is on the ignition side of the engine. The tach is driven from pulses on the charging side-the two issues are not related.

Re: 1994 115 Johnson operating temp, thermostat id, tacho operation

DargelJohn said:

Your temp should be 140-150 degrees. Easy way to check is to get an IR Temperature gun. Harbor Freight has them for cheap.

When the tach drops to zero, is the motor dropping as well? Reg/rect is a common tach problem, maybe you have a loose connection somewhere.

Click to expand...

G'day Dargal thanks for the input appreciated. The thermostats tested good opening at 58c or 136F wide open at 63c or 145F although one was a little slower than the other only just noticeable by the naked eye and they are closed at 58c/136f. Motor does not drop rpm when tacho drops out, performs no problem at all very happy with performance. the tach just simply quits like the flick of a switch.
Dean

Re: 1994 115 Johnson operating temp, thermostat id, tacho operation

emdsapmgr said:

The recommended operating range for that engine is between 4500 and 5500. Best to stay at the very top end of that range, or 5500-5700 for optimum perf and fuel economy. The power pack will limit spark beyond 5800, but that is on the ignition side of the engine. The tach is driven from pulses on the charging side-the two issues are not related.

Click to expand...

G'day emdapmgr, I realise the rev limitation is not connected to the tach problem may be I have not reved it to 5800 yet as the motor has not yet missed or anything like that that would suggest an electrical break down of some sort. Still has me beat how it functions fine till getting near that 5-5 to 5-7 rpm the tacho should read regardless of what rpm the engine is doing correct? I'll keep hunting around for more possible answers or suggestions. Thanks for responding to my questions appreciated, thankyou.
Dean