03 9.8b 2stroke cooling problem

[RICHIE B]

I sure could use some help here. My motor seems to overheat at high speeds ( It starts to lose power and it steams for a few seconds when i back it off to idle speed ). At low speed its fine. I changed the impeller and flushed it. Water is exiting the indicator port. When I flushed it I ran it for about ten minutes hoping to feel a change in the water temp in the exhaust wash, it never changed.( checking for an opening thermostat) I could keep my hand on the head at this time but wasnt able to put it under a load. No water came out of the rear water exhaust port just a little exhaust and just a little spit. The piece of crap SELOC manual I bought does suggest these sympyoms as a possible head gasket leak. Needless to say I have a head gasket and thermostat in my hand. If anybody knows the torque value for these head bolts would you please let me know. And any other info would be greatly appreciated.

 

[pvanv]

Re: 03 9.8b 2stroke cooling problem

I take it you have a Tohatsu/Nissan M9.8B (or NS9.8B), right? Did you replace the whole wp kit? If you only did the impeller, I would do the cup and plate as well (install a kit), because the side clearance on the impeller is important, and a few thousandths of clearance there, in the form of a wear groove, could cause your issue. You could also have a chunk of old impeller blade jammed in the water system. If so, backflushing the motor with the LU off might blow it out of the water tube.

The Factory service manual, available from any dealer, has the procedures and values (including the tightening sequence for the head bolts). What does a compression test show? What doe the plugs look like? If water is getting into the chambers, the plugs will be blasted white. If combustion products are getting into the water stream, you will probably be seeing exhaust coming out of the telltale.

The telltale stream temperature will not change a lot at idle, as it is primarily showing pressurization of the cooling gallery in the base of the motor, not the spent cooling water coming out of the head.

 

[RICHIE B]

Re: 03 9.8b 2stroke cooling problem

thanxs for your reply. I did change impeller with kit/ no pieces of impeller were torn off .And I did find info on this site for the torque specs. 21 ft lbs or 185 inch pounds. I should have specified tahatsu but you knew that. Any way I replaced head gasket and thermostat ( at this point I was going to change thermo ) runs like a champ. again thanks for the reply