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Mariah Z2350 Merc 7.4 overheat
I just bought a 1993 Mariah Z2350 with Mercruiser 7.4 and Bravo 1. It ticked over fine out of the water with hose attachment, and on the trip out of the wakefree zone. Moments after opening the throttle to about 2/3, a buzzer sounded, and thick acrid smoke poured from under the transom cover. I immediately shut down the engine and noted thick smoke coming out of the empty cassette player hole. On opening the storage cupboard door under the instrument panel, the cupboard was full of smoke. On opening the transom cover, masses of smoke came out and cracking was heard (like frying bacon).
Once the smoke creared, I could see water coming in through about an egg-szied hole in the bellows between the exhaust down pipe and exhaust lower manifold outlet on the port side. On moving all passengers to the bow, the water no longer came in. The engine appeared (smelt) very hot. Water drops dropped onto the port manifold quickly boiled and evaporated. After returning home, the engie will start fine. I have not run it for more than 1 second though. The hole in the bellows appears more of a melted effect and carbonized edges rather than a split. I am completely new to boats, but have some car experience. I am seeking advice as to what could be the problem, how to fix it and a reputable repair shop near Springville, Utah. I appreciate any help. Thanks Clive (801)310 0480 |
I ran into a similar problem at the beginning of the season. I found that the impeller in my water intake pump had disintegrated and the heat from the overheating exhaust had melted a hole in the bellows. It also melted my shifter cable housing so I was unable to shift. All in all it cost me about $500.00 in parts and I did the work myself.
I usualy change the impeller every two years to avoid this problem, but I didn't this time and it got me. |
Hello Clive,
Sorry to hear of your problem. As John said, it definitely sounds like the impeller in the pump. Unfortunately, using a garden hose on dry land doesn't tell you what condition the pump impeller is in as the water pressure from the hose forces the water through the motor so even with a bad impeller, the motor temperature will appear normal. The only real way to check the impeller function is to submerge the outdrive in a large tub of water or the lake and have the impeller do the work in drawing the water. I suggest you take it to a authorized Mercruiser service person for a complete checkup and repair. It's real important to have the motor checked out to insure it didn't sustain further damage from overheating. In the future, consider the impeller as something that needs to be changed on a regular basis like oil changes, your service person can advise you of the interval. Click here for service centers near you. There's 1 in Springville, 1 in Prove, 2 in Orem, 1 in Heber City, 3 in Draper and so forth.... Good luck and let us know how it turns out, WetWilly |
Thank you. I dropped it off at Jones Mobile Marine Service, Payson last night for a full check out. It has a 15" dia. SS 4-blade prop with considerable wear. Do you know where I could find a good used replacement. I think it needs 19" pitch, 4 or 5 blade.
Regards Clive |
Hi Clive,
eBay is a good place to look for props. just remember to look at the sellers feedback and return policy in-case you have any fitment issues. As for the pitch, I assume you don't know what your WOT RPM was, so it's going to be a little hard to tell if you need a different pitch. May I ask why you think you need to re-pitch? WetWilly |
Pitch
I don't know what pitch the prop is that is on. I have looked over it and not found any text to tell what the pitch is. I talked to a guy at SS Marine in Orem and he advised that the pitch should be about 19". I am ready to learn different if that is the case, in fact, what I should really be asking is what would be the correct prop to put on it. It presently has a 15" four-blade unit.
Clive |
Hi Clive,
The pitch information is probably on the inside of the prop hub requiring you to remove the prop from the outdrive first. Now when you said your prop had "considerable wear", did you mean it was dinged up or bent? Now unless your prop is really bad, I suggest get your motor issue fixed then test your Mariah on the water to see how she actually performs. As it is, you may already have a 19 pitch prop on it now. If you get back on the water with your current prop, see how she takes off, how long to get on plane and what your max RPM is at WOT (Wide Open Throttle). Just be careful not to go beyond 4800RPM at WOT, you don't want to over rev your motor. One thing to remember, since our boats only have one forward gear, the goal is finding an acceptable compromise between takeoff and top speed performance. WetWilly |
Thanks,
it is going in for repair estimate today. The prop doesn't seem bent, just a lot of dings. I filed off the worst curled over bits and it doesn't look anywhere near as bad now. I was careful not to file more off one blade than another, and only took a little metal off. Clive |
I have my propeller reconditioned every year or two. There are a lot of shops around that will use a computer to read your pitch, balance, etc. They then can fine tune it to get the best performance. Mine is stainless so I pay a little more to have it polished so it looks good too! Even a small vibration over a long period of time can cause damage. :)
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