Mariner prop questions and RPM questions

[Johnshan]

Any idea the RPM this 1985 Mariner 30 M (30 hp) motor should run?<br /><br />Its pushing a starcraft 14' thats rated for a 40 hp. It supposedly does 20 mph (a friends speedometer on his boat said so but who knows). But it doesnt seem to rev very high at all. In N it revs VERY high if i want it to but in Forward it just doesnt rev up. <br /><br />The prop is the factory "All load" prop (according to Cabela's replacment ones). Im assuming that since this boat is kinda heavy maybe I need a diff prop? Im not sure of how high this motor should rev, anyone know? I heard 4500-5500 RPMs? Also pulling a tube, it barley does it and takes forever.<br /><br />I would be happy with a nice crusing prop, I can live without the tube since friends have boats of their own which we use to tube.<br /><br />Usually theres 2-3 people in the boat, figure 800 lbs in boat including motor/gas people. <br /><br />How do I find what its doing now for an RPM? Where do I hook the tach? Thanks!<br />-John

 

[JB]

Re: Mariner prop questions and RPM questions

Hey, John. I agree. It sure sounds to me like you are over propped and unable to reach max rpm at w.o.t. I also agree that your engine should reach 5500rpm with a light load. I would expect that Mariner 30 to get your Starcraft up to 25, and to do it with a pretty nice hole shot. You don't seem to be getting either, and I don't know what to tell you to do without a tach. An aftermarket tach should cost you less than even the cheapest rebuilt prop. The tach should come with instructions or the dealer who sells it to you should provide instructions for hooking it up.<br /><br />Good luck.<br />JB

 

[Johnshan]

Re: Mariner prop questions and RPM questions

Well today I took it out again, and I had a friend adjust the carb screw as I ran full throttle and when we reached a certain point it picked up a lot of speed and went really well. <br /><br />Problem is as soon as I went to below 3/4 throttle it wouldnt run well at all, barley started too.<br /><br />Set the screw back to where it was (About a full turn out? if i recall). <br /><br />The screw is on the left side of the carb if look at it straight on, right in the middle of the carb. Now on the other side theres aanother screw on the top, but its tight, has no spring on it either so i didnt touch. <br /><br />Any clues? When I first got this setup it ran very well and did 25 mph says a friend, now im not sure what it does but it seems to be getting slower and slower everytime I take it out, now i realize its not in my head.<br /><br />Any ideas? Thanks everyone. By the way all gas is fresh and at max like 3 days old (i use the boat a lot).<br />-John