Need some help

[Highmaster499]

I just recieved a 1988 Starcraft Center Console that has a 1988 50 hp Mercury.<br /><br />It starts great and runs fine for about 15 minutes and then the engine slows to an idle speed. After a few minutes, it throtles up to full RPM again. I personally believe the boat is under-powered and wondering if that lack of power is causing the engine to overheat and causing the speed loss? Any thoughts would be deeply appreciated....<br /><br />Thanks

 

[Trent]

Re: Need some help

Dont know the size of your boat to say if its underpowered or not..But thats not the problem with your engine. Does your overheat horn work? Is your water discharging from the engine normally..Tale tale peeing water? Cant remember off hand if that engine has a secondary on the stator to go to auto "slow down" for overheat or not..Its been along day. You have a problem but the size of your boat is not it. More info would help.

 

[Highmaster499]

Re: Need some help

Trent,<br /><br />Thanks for the speedy reply......know how you feel, been working on the Merc. all day. <br /><br />The overheat horn works and the water is discharging great (have two other boats with big Mercs, but this little bugger has me stumped) I don't believe the 50 has the auto slow down, but I'll verify that in the AM. If it does, that certainly starts to pin down the problem. Once again Trent, thanks for the ideas...... It's appreciated. Get some rest!<br /><br />Carl

 

[norman158]

Re: Need some help

is the primer bulb spongy during the rpm drop?

 

[Highmaster499]

Re: Need some help

Morning Captain,<br /><br />Thanks for the response.<br /><br />No, that was one of the first things I checked as I thought it might be starving for fuel. The ball is hard and remains that way through the whole episode. Also of interest, the RPM range from idle to WOT is pretty near text book perfect until the little bugger gets tired and decides it don't like my throtle settings and simply slows to an idle speed. By the way, the motor does not shut off it simply hits the idle range and then after a couple of minutes, is more then willing to run at high RPM again for 10/15 minutes..... Sure has me scratching my head.... Any thoughts would be appreciated. <br /><br />Should of mentioned in my opening post, this starcraft boat is an 18 footer with the ugliest dead-rise I've ever seen. Seen tug boats with better lines. Still wondering if that little 50 Merc. is over-matched for the weight of the boat and that ugly dead-rise. It will plane out but it takes some time and effort. <br />Best<br />Carl

 

[Gold Bear]

Re: Need some help

I had the same thing happed to me on a 50 HP Merc. I found out that the fuel pump diaphram was stretched.<br /><br />After fixing that it ran great.<br /><br />If you have a tachometer you can determine if the propeller is sized right for the boat. If at WOT it runs @ 5,500 rpm's (or whatever the engine is rated for) then the propeller is the right size. <br /><br />Other than that, all you can do is install a larger engine.<br /><br />Good luck, hope the diaphram works for you.<br /><br />Gold Bear

 

[Highmaster499]

Re: Need some help

Gold Bear,<br /><br />Great idea, it's one of the few things I haven't checked. Sure appreciate the help!!!! <br /><br />Best wishes,<br />Carl