speed problem

Bought a 19' javlin bassboat with a 150hp outboard, it would top out at 56mph when i first took it out. now im only getting 46mph and the prop felt like it was slipping sometimes when running top speed.

took the SS prop with a 23" pitch off and a friend gave me an Alum. prop with a 19" pitch, put it on and still running 46mph at full throttle. I also have a GPS and it says 46mph also.

Think this 150hp outboard motor should run faster than 46mph even with the Alum. prop, any ideas why im not getting the speed i should? Thanks for any info.

when you drop pitch rpms go up and top speed goes down. you dropped 4" of pitch so your hole shot should have improved while top end fell off. the 23 ss prop should be much faster than the 19 alum. it sounds like to me the ss prop has a spun hub if its slipping

What RPM are you running?

Jackplate? How are you trimming?

Sounds like the first prop may have a spun hub.

No jackplate
running about 5400 rpm
I trim down for take off and slowly trim up once up on plane somewhere between half and three quarters

I also thought the first hub was spun thats why I put the Alum. prop on to see what it would do. This boat jumps right out of the hole with that 19" pitch prop. but I still think 46mph is to slow for that big of an outboard.

Have noticed a little white smoke from outboard when running at an idle but motor sounds really good, thought maybe i was running a little rich on fuel

Going from the 23P to the 19P should have gained you around 800RPM. If you are running 5400 with the 19P, you shouldn't have been able to turn a 23P more than about 4500. I'm assuming the props are the same diameter.

I have a 150 on a little heavier boat, and can turn a 21P prop at 5700RPM and run 55MPH. I'd kind of expect you to see that same kind of performance with a little more top-end with the 23P since your boat is probably a little lighter.

I'd expect you would over-rev your motor with the 19P, and since you aren't I have to wonder if you have an engine problem, tach problem or if you are carrying water inside the hull making the boat a lot heavier and causing the motor to work harder.

You can check the stainless prop for slip by making a mark with a permanent marker across the gap from inner to outer metal, running the boat and seeing if they still align.

To really figure it out, you need accurate RPM numbers and GPS speeds with both props, and a check of the hub on the stainless.

Thanks for the info, I will do what you have said with making a mark on the hub and prop to see if they still align. ( great idea ) I will also get rpm and gps speeds from both props and get back with you in a few days.

Im not carring water as I always run the belige pump once in a while and keep the hull empty of water due to sometimes I forget to shut off the live well when the crappies are hitting.

Also going to replace the plugs, still wondering if maybe my jets in the carb. might be clogged a little?

Again thanks for your help.

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Originally Posted by BassboatCrappie

Im not carring water as I always run the belige pump once in a while and keep the hull empty of water due to sometimes I forget to shut off the live well when the crappies are hitting.

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It is possible for water to get into the area where the flotation foam is, and it then can't get out to be drained. This usually happens as a result of a crack or unsealed hole in the transom.

How do I check for water in that area of the boat or better yet if I find some how do I get it out?

Quote:

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Originally Posted by BassboatCrappie

How do I check for water in that area of the boat or better yet if I find some how do I get it out?

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If you have a transom mounted transducer, you can pull one of the mounting screws. Just be sure to seal it before reinstalling it.