1989 Laser 18' prop question

[bownpole1697]

New to the group. I have a '89 Laser 18' bass boat with a '96 Johnson fast strike 150. the boat only runs around 55 - 58 mph at any height on the jack plate. It has a Raker 14.5" x 26p on it and i am only able to get 5200 rpm at WOT. The engine is perfect so no issues there. what would be a good prop to start out with? Thanks for any help

 

[Sea Rider]

Welcome to Iboats,

With boat running parallel to water level while trimmed to 90?, dial a jack plate height to achieve water flow at plane to skim right under small upper water deflector plate. What's factory stated min-max wot rpm range ? If at 5200 wot rpm is low will need a less pitch prop to pull wot revs around middle range, but max is preferred as usually loaded.

Happy Boating

 

[jimmbo]

96 150 Fast Strike WOT rpm 4500 - 5500
Raker is a very good prop, unless it has had a poor rebuild. But 55 - 58 mph 5200 with a 26 in prop is showing between 17 - 21% slip which is very high. How are you getting the speed, GPS?
Is the hull straight? No hooks?

 

[bownpole1697]

Yes from GPS. Hull is perfect. These boats are very light. New to this prop selection stuff. Out of the hole it launches violently and comes to plane way to quick. It will lose its grip and you have to stop and start over. Once its on plane you can let it eat all day. 55 - 58 mph is loaded speed. My wife myself fuel and gear. Just need to know if there would be a benefit to going to a smaller pitch prop.

 

[Sea Rider]

If max wot rpm range is 5500, at 5200 OB is revving around middle wot range which is good, one less pitch should pull wot revs towards max range . Combo will better hole shot but will lose slight top end speed. To start over again, first time reading this kind of issue, seems OB is badly trimmed, deck weight badly distributed, OB sitting at a incorrect transom height or a cocktail of all 3.

Is current prop in good working order, no spun hub ? check...

Happy Boating

 

[jimmbo]

Yes from GPS. Hull is perfect. These boats are very light. New to this prop selection stuff. Out of the hole it launches violently and comes to plane way to quick. It will lose its grip and you have to stop and start over. Once its on plane you can let it eat all day. 55 - 58 mph is loaded speed. My wife myself fuel and gear. Just need to know if there would be a benefit to going to a smaller pitch prop.

Where is the anti-ventilation plate in regard to the bottom of the hull? Even or higher? If higher, how much? The RAKER can run very well partially out of the water. Are you trimming in fully prior to launching?

 

[fhhuber]

55 is pretty good speed for that size boat with that engine...

You might find a prop that gives a little more, but you'll need to find shop that will let you test out props on the lake.
As mentioned above, a little less pitch to let the engine wind up to 5500 rpm.... and maybe a little more diameter to reduce the slippage.

 

[bownpole1697]

Thanks for all the input guys. I went to a 14.5" x 24p Raker and now she is doing much better. It doesn't lose grip at launch and is still getting 57mph at 5400rpm.