Finally got the info!

[mtblackdog]

Well we had some water open up here in Montana(really strange for Feb 9) so I fially go my new boat out 16foot Lund Tyee II with a 1991 90 horse Johnson with very low hours (does have a fin on it), well new to me anyway. So Im looking for some prop ideas. The current prop is 13 1/4X17 and I topped out RPMS on plane at 5050. We were running in 30 degree weather at 4800 feet in elevation. The boat seemed nice on the top end but was really doggy and boggy on the take off and hole shot. Really pushes the rear end of the boat down. Any ideas price is not a concern I just want good performance and I want to be able to pop out a skier once in a while.

 

[gatorred]

Re: Finally got the info!

what type prop is it alum or ss alum try 15 pitch more rpm 5500 more like it

 

[walleyehed]

Re: Finally got the info!

We're about 700-800RPM short....<br />The engine may need to be raised on the transom some, even with a 15P, to get to 5700-5800.<br />If you have a dealer near, you need to pull a main fuel jet and check the number/size and see if it's the stock, sea-level jets.<br />I would recommend you go at least 3 sizes leaner at 4800ft...that will gain you a couple hundred RPM on the top and increase your fuel economy greatly. The timing could also be advanced about 2 degrees and help a bit more.<br />The performance is mostly up to you and how much you want to work the set-up, but the Jets must be correct to get any power to speak of at that elevation....I've dealt with it for years at 4000ft.

 

[mtblackdog]

Re: Finally got the info!

Thanks guys the prop is aluminum. I kinda of thought that 5050 RPMs was a little low. Figured it was a due to altidude, I have worked on snowmachines alot. But Im a complete rookie on a boat motor. I do have alot of tools, and I bought a shop manual on the internet, so I guess Ill go at it. <br />Walleyehead- Any prop recommendations or should I try and get the carbs straigtened out first and then see where Im at on RPMs<br />Thanks <br />Jamie

 

[mtblackdog]

Re: Finally got the info!

ttt

 

[walleyehed]

Re: Finally got the info!

I'd pull a jet, check with a dealer and find out what the factory jets are...compare the numbers to see if it has been leaned down any. If it hasn't, you need to drop 3 sizes.. so if you have (example number)058's, you need to drop to 055's (55 thounsanths). this will make quite a difference, but I don't think it will bring the R's up where they should be, but for a reference point, that needs to be checked/done first.<br />The timing should be checked as well, make sure it's at least at the factory recommended position, then we can advance it about 2 degrees.<br />Check into the jets first and report back and we'll go from there.

 

[mtblackdog]

Re: Finally got the info!

Kenny-So when I lean the jets up 3 sizes, and advance timing. What about a 15 pitch prop instead of the 17. Im running about 35 mph top speed right now. Since Im a total rookie what does a 15 pitch vs. 17 pitch prop do for performance. Common sense tells me that the 15 rotates faster but wouldnt you lose torque for say popping a water skier out. Sure appreciate you answering all my questions. The problem with the internet is you cant just sit down and buy a beer for guys like you who help us rookies out so much. Jamie

 

[mtblackdog]

Re: Finally got the info!

got it on the johnson forum above thanks!