Merc. Inboard 01 350 Mag. MPI Cooling Issues

[Limited-Time]

Quick overview 01 350 Mag MPI straight inboard (Centurion Ski Boat) raw water cooled. Less than 50 hours on engine, Temp climbs at speed, at Idle temp drops. port exhaust manifold almost cool to the touch starboard side manifold HOT, same with cooling lines. At idle Temp is around 170* any thing over idle temp begins to climb. Engine seems fine otherwise great power runs smooth other gages in normal range. Also serpentine belt seems to be wearing more than normal, lots of belt dust, seems excessive for a low hour engine. This same issue prompted a trip to the shop 2 years ago (just over 50 hours on meter), replaced impeller, changed belt. Next time out cooked engine. Merc warranted all parts, (new long block) owner paid for labor. Owner would like to be back on the water yesterday.

 

[tommays]

Re: Merc. Inboard 01 350 Mag. MPI Cooling Issues

the raw water pump would be the most likely thing to eat the belt and cause low enough water flow to overheat<br /><br />BUT anything else on the same belt that was bad could also be binding things up <br /><br />i dont no if you have the plastic one but have read here on other posts that the cover can be made to tight and cause problems<br /><br /><br />tommays

 

[nms1991]

Re: Merc. Inboard 01 350 Mag. MPI Cooling Issues

Check the hot running side exhaust for restriction in manifold or muffler posssibly broken loose baffle in it. Also make sure water is flowing thru the exhaust manifold.

 

[waterone1@aol.com]

Re: Merc. Inboard 01 350 Mag. MPI Cooling Issues

I would start by pulling the water pump and closely examining the impellor and inside of pump. I would also look for any vibration, noise or signs of binding of the pump shaft bushings, if any doubt, replace the whole pump. Of course, check your thru-hull , strainer and any filter before the pump. If you are able to, disconnect the water hose from the thru-hull and connect the hose to a garden hose that is connected to a water faucet. Start the engine and slowly raise the engine rpm's, after about 1500 rpm's the suction from the water pump should start collapsing the garden hose ( the pump should be sucking more than the garden hose can deliver). If not, you either have a bad pump or a restriction after the pump. By any chance is this boat fitted with a fresh water flush kit ?? I've seen some improperly installed (yes, by dealers) that can cause this.

 

[Limited-Time]

Re: Merc. Inboard 01 350 Mag. MPI Cooling Issues

Thanks for the responses.....Pulled the seawater impeller yesterday. Looks bad, half the veins torn 2/3 the way down the sides, the surface opposite the shaft, looks burnt. From the shape of the impeller you would think it had a ton of hours on it, not less than 50. Will be getting impeller kit this PM and reassembling this eve. Will let ya know how it goes. <br /><br />Also no sea water strainer in the system. Is it common to omit the strainer on inboard ski boats? The hull is a Centurion BTW. I am wondering if there isn’t an issue with the pick up placement or type as this is the second impeller to cook in less than 100 hours. Plan on checking the system for flow after we install the new impeller. Thanks again.