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90hp Alarm only at WOT

D

darlington_john

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"My 90hp can run all day long

"My 90hp can run all day long < 5200rpm but once I run wide open for a minute or so, the overheat alarm goes off and the motor goes into safe mode and idles. I can run it back up to 5000rpm and it is all good.

Motor has 300 hours, only freshwater use, and I changed out the impeller last year and it has only run about 1.5hrs since then but I thought it was the impeller since there was less water coming out of the pee hole at WOT and I mean a lot less. Once I changed out the impeller, at WOT it seems to have a very good stream.

Any ideas??"
 
"There are several things that

"There are several things that can cause it. Generally, it is a partial blockage or fractured impeller.

1. When you changed the impeller, if pieces were missing from the impeller, they could be lodged around the thermostat and limiting flow.

2. You may not have installed the new impeller correctly.

3. A restriction or open at the backwashing port on the back of the engine.

4. There could be a restriction in the exhaust (ie: if the motor has been sitting, little critters can make a nest up in the exhaust...I have helped a another dealer lately that had a bees nest in the exhaust section of the lower unit.)

I would suggest, removing the lower unit and removing the thermostat. Check for debris or impeller pieces at the thermostat.

Then...backwash with a hose from the thermostat.
Once you have good flow and no additional pieces coming out the water intake tube, have someone plug the water intake tube with their finger and make sure the flow is good out the indicator and out the exhaust.

Make sure you used all the appropriate gaskets in the water pump and the cup in the housing is oriented correctly."
 
"John, only thing extra to wha

"John, only thing extra to what Mike says,

make sure all your bolts around the impeller unit are done up as tightly as they should be. At WOT, there is a lot of turbulance down there, and air seems to make its way in through loose fittings. I spent lots of hours on mine, pulling it apart re fitting and doing the same again, and then I tightened the bolts a little tighter than I should have...and water came out in a nice steady stream at all revs..."
 
"Thanks for the replies. The

"Thanks for the replies. The impeller was changed out at a local Honda dealership, the old impeller was in good shape with very little wear so I hope that addresses the first two points. I was initially thinking that the impeller was the problem as the stream was getting worse and worse out of the pee hole towards the end of last summer. Once they changed out the impeller, there was a good stream at idle and at higher revs.

Given that it cost me $310 to change out the impeller, I'd rather do the balance of the work myself so what manual should I pick up to do this work myself? I've done a lot of work on other outboards so this should not be difficult for me."
 
"As I'm sure most every on

"As I'm sure most every one else here will recommend as well, get the ONLY manual that is worth buying. The others, (primarily Seloc) are much less expensive but, as the Snap-On tool guy say's; "quality isn't expensive...it's priceless"

I think this link will get you there. Just plug in your motor's numbers and get out the old card.

http://www.helminc.com/helm/Result.asp?session=946550B31AA24E1C8FA93B330B049646& Style=helm&Mfg=AHP&Make=MAR&Model=OUTB&Year=&Category=1&Keyword=&Module=&selecte d%5Fmedia="
 
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