Gauge and hose was already installed when I bought boat, but hose was not hooked up. Where do I splice in the hose on a 98 Mariner Optimax? I dont see the hose like the newer ones have and I know the tell tale will not give correct pressure. Thanks

I think my 150 was between the heads at the rear of the engine. The port thermostat has a tube going to a Smartcraft sensor.

I spliced into that with one of these things. Push in to connect fitting.

Mine is not setup for the smartcraft stuff it is too early of a model but I will see if it has the hose between the heads. The hose that is on it is a pvc line that is maybe 1/8" does that sound right? Seems a little small to me. When i blow in the hose it goes up to 5psi on gauge. I cant get it to go much higher by blowing in it which makes me wonder if it is kinked also.

Thats big enough, your measuring pressure not volume. Only thing the smaller hose will do is react to changes a little slower. How are you blowing in the hose, with compressed air? The gauges go bad. Tip after getting the gauge working right pour a little anti-freeze in the hose.

I blew in the hose with my mouth. Once I get everything right I will put some antifreeze in before I hook it up, good suggestion I didnt think of that.

To prevent damage to the gauge remove line from the gauge. Blow back through the tubing to remove all water. Then tighten the connector and you shouldn't have any problems. I replaced three gauges before I learned this lesson, never another problem.

I took it to the local repair shop and he showed me where the plug should be in the block and I took it home and removed the middle cowlin and couldnt find a plug anywhere. I ended up installing it it the hose between the thermostats but I am not sure if that is correct. I am reading a little ovr 2 psi on idle and 5 psi wide open. Motor was suppose to have a new pump installed last summer and seems to have good pressure coming out of tell tale. I dont know if gauge is bad, line from gauge to motor is too small, or if I have it hooked up in the wrong place. Any ideas?