What did I cook?

I am looking for some feedback about my boat problem. I have a Maxum 20ft with a 5.7 Mercruiser and an Alpha One, Gen 2 drive. I replaced the impeller myself this winter and ran it on the muffs at home a few times, once for 15 minutes, with no overheating problems. I took it to the lake Saturday for a cruise and it overheated big time after about 5 minutes. I smelled burning and saw the temp guage moving so I shut it down. I had a bunch of smoke coming from the engine compartment and sprayed it with the extinguisher. I was still hearing crackling and popping like there was fire in the bottom but couldn't see anything so I sprayed it again and after a while the smoke and crackling stopped. Towed it home and looked it over. I don't see anything in the engine compartment that looks like it burned or even got terribly hot. In fact, the hose for the blower, which is very flimsy, is still intact so I don't think I had fire in the engine compartment. I think I had fire and melting in the space between the engine and the external drive. I notice that one of the rubber hoses between the two is full of holes and charred.

My symptoms are that everything electrical seems to work but the shifter/throttle mechanism won't move and the motor won't start, probably because I can't shift the boat into neutral or whatever. I also lost the hydraulics for the transom. the hoses must have melted because all of the fluid is gone and the transom won't move, although the pump motor works fine. I did not lose any of the fluid that lubricates the transom as my reservoir is still full.

I still don't know what went wrong. I can only think that I might have installed the impeller backwards.

After all of this information, here are my two questions...

1. If I installed the impeller backwards (with the blades curved the wrong way) would it fix itself once it started rotating?

2. Why would the boat overheat on the lake when it wouldn't overheat with the muffs in my driveway?

3. How many things go through that bellows area that might need to be replaced?

Thanks in advance for any help.

Re: What did I cook?

Even if you installed the impeller the wrong way, they may not all turn around the right way, but it would still pump enough water to not burn things up that quick.

I would suggest you pull the drive and look at the raw water pump as a first step.

Re: What did I cook?

The impeller that I replaced was the rubber one in the drive down by the prop. Just to clarify.

Re: What did I cook?

Yes, that's the one. Even new parts can fail. That impeller is the first thing you check. WAY to many things can go wrong with it.

Re: What did I cook?

red95vertible said:

2. Why would the boat overheat on the lake when it wouldn't overheat with the muffs in my driveway?.

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When running on muffs the water pressure of the hose will circulate water through the cooling system even if the impeller isn't working properly. On the lake you don't have the hose pressure to help.

Re: What did I cook?

You most likely melted the shift cable also, it passes very close to the Y pipe.

Re: What did I cook?

I just looked in my Seloc manual and noticed that the exhaust pipe, shift cable, and hydraulic hoses are all next to each other on the inside of the transom plate. That's where my problem is.

Does anyone know if you have to pull the engine to replace those items? My boat is a Maxum Fish/Ski with at deck over the engine so when you open the engine cover you see that the engine is surrounded by wood with access panels to reach certain places. Looks like it would be tough to get down in there and replace those items.

Thanks again.

Re: What did I cook?

red95vertible said:

I just looked in my Seloc manual and ...

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:facepalm: Use the factory manuals. Available HERE....

You may not NEED to pull the engine, but it will be SOOO much easy if you do....

Re: What did I cook?

Does anyone know if you have to pull the engine to replace those items?

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Ayuh,... As Chris says,... It'll be SOO much Easier if ya Do...