Z300 2 stroke overheating issue, or ???

[Secondchance2012]

I am hoping I can get some help on here to figure out what is going on w this motor. Let me start with the whole beginning.

The boat is a 2001 Wellcraft center console pro tournament series 210. She had a Yamaha150 salt water series motor (#5 and 6 cylinder had no compression), but that got changed for a 2004 Z300 w 906 hrs. The boat sat for 14 years due to neglect and mistreating. So I was challenged to bring it to life again. I put new gauges in the boat, I have replaced the poppet valve, the thermostats were changed, the impeller was changed.

The problem I am having is that she wants to overheat(alarm blaring) (tell tale not peeing) when running her in the river right out of the starting gate. we can't even get 100 yards off the dock. When she is home and you hook the hose to the flush she will pee and run cool. I am confused.

Is there something I am missing. This is smashing my head to the wall trying to figure this out without taking her to a dealer. Any help would be great or is there something else going on she is trying to tell me .

Thanks Joe

[99yam40]

do your gauges work and show it is an overheat alarm?

did this 300 sit for 14 years after it was put on the boat?

sounds like the water pump is not pumping water , did you replace just the impeller or the kit and housing?

[rodbolt17]

do you have the correct shaft length on the motor?
what is your transom height?
what is the full model number?

[boscoe99]

Hardly anyone wants to tell us what motor they have. Hey, it is gray, isn't that enough?

The boat has a 25" transom. If you have a Z300TXRC or a Z300TURC installed the motor will either be the correct shaft length (first model) or too long (second model). In which case there should be adequate water available to the motor for cooling purposes.

Now if you have a VZ300TLRC installed then it is the wrong shaft length for the transom. In which case when the boat gets on plane the lower unit water inlets can't get the water they need.

As noted, the alarm blaring does not necessarily indicate the motor has an excessive temperature. The are other instances in which the alarm will be made to sound. You might not have an over temperature problem at all. But given that the tell tale goes away when the boat comes up on plane indicates to me that there is either a boat related issue causing a lack of water flow or perhaps the water inlet grates are out of position. Possibly the motor is too deep. Contrary to conventional thinking some VZ/Z motors will have more water pressure when they are mounted higher out of the water.

[pstephens46]

Didn’t some yahoo recently have the grates installed in the wrong direction?

[boscoe99]

If they can be installed upside down or bass ackwards some yahoo will do it.

[Secondchance2012]

The motor came off a 32ft Contender, and has same shaft length to the 150. the grates were correct , she is a Z300txrc edition.Well to make a long story short . I decided to pull the whole lower down and check with the lower unit from the 150.

I guess never take someone else's word when they say something is done. The tube that runs into the impeller housing was missing a collar and a rubber grommet. Once I pulled the one off the 150 and put on 300 and bolted all back together tell tale pisses like a race horse at idle in the water troth and runs 110-120 degrees. Now I just hope she behaves on the river.

[boscoe99]

Thanks for the feedback.

[walleye1]

OH BOY