4HP Yamaha - Water problem

[ryanabigail]

looking for advice on the following outboard - 1999 Yamaha 4Hp 2-Stroke [/LIST] model - 4AC Longshaft, i have been having a problem with the water flow through the engine, I changed the impellor about a year ago and thought the engine was fine as it started and ran with water coming out of the 'tell tale' hole. I never used it on the boat, however i have nearly finished a refurb of the boat and tried the outboard, it started and ran fine with water again coming out of the 'tell tale' though perhaps not as fast a flow as it used to have, however a the engine warmed up the flow slowed to a trickle and then steam, i stopped the engine. This had taken about 1 minute. I let it cool down and tried it again with the same result. I stripped the leg and cleaned the impellor and housing and put it all back together, the rubber impellor is still as new as it has not been used. When stripped i noticed the fit of the drive shaft through the outer plastic impellor housing was not very tight. I put the leg back together but still got the same result, water pumping through slowly then dropping off and turning to steam as the motor warmed up. I ran a hose through the tell tale and water came out of the tube that feeds from the impellor, i also ran the hose through the tube from the impellor and this came out of the tell tale ok. <br /><br />Is it possible that the loose fit of the drive shaft through the impellor housing is causing a loss of pressure in the water system or is there another possible cause? <br />Any advice would be greatly appreciated.

 

[huanca]

Re: 4HP Yamaha - Water problem

my impeller blades sheared form the black plastic that fits around the shaft. take yours and and bend it to see if it is vulcanized all around. it may be slipping as mine was. <br /><br />looks like the water passages are clean so it sounds like it is the impeller. geta new one, less than $ 20 and much cheaper than a new engine! <br /><br />good luck

 

[bigbrownbuku]

Re: 4HP Yamaha - Water problem

i repaired 3 similar problems this summer. your engine suffers from corrosion build up internally.<br />the telltale on a 4hp yamaha really only tells you water is making it to underneath the powerhead. it is beyond this point you have a blockage. remove your powerhead and exhaust cover and clean out the corrosion/salt buildup. at the very least to check the water tube grommet at the powerhead base.

 

[ryanabigail]

Re: 4HP Yamaha - Water problem

BenC - you were spot on, the water passages around the cylinder were totally blocked with hard salt build up and a 'Gel' that had formed, sorted this ot and the 4 studs that snapped off when removing the covers and the engine is as good as new,<br /><br />Cheers!