Am I over Propped?

[robertdale]

I'm new to boats and I just purchased a 1978 glasstron bass boat with a 1989 Johnson 150. The boat is only turning about 4200 RPM at WOT. I am told maybe the prop I have is too much for my combo. The prop is a SS Raker 14.5X24. It tops out in the upper 50's with one person Low 50's with 3. What should be the optimal size prop I should get?

 

[kenmyfam]

Re: Am I over Propped?

First thing would be to verify that the tach reading you are getting is correct. Next make sure that your boat does not have waterlogged foam that is weighing it down. Give it a good decarb and go from there. Make sure you are trimed correctly as well. It may not be as simple as a prop swap.
The real experts will I am sure be along shortly with their input.

 

[Dhadley]

Re: Am I over Propped?

Which Glastron bass boat? Does the hull have a pad? Jackplate?

 

[robertdale]

Re: Am I over Propped?

hp-171 model
I'm not sure what a pad is. yes it has a jack plate
boat is not water logged as i can tell.

 

[kenmyfam]

Re: Am I over Propped?

hp-171 model
I'm not sure what a pad is. yes it has a jack plate
boat is not water logged as i can tell.

You may have to weigh the boat and motor and trailer, then launch the boat and weigh the trailer. Do the math from there to see if you are "heavy" or not. That is what i did with my outfit as it looked a little low in the water when I first got it. Mine worked out fine. It was just the fact that i had the max HP outboard on it I think.
You will have to find out your original hull weight, the weight of your outboard and allow for fuel on board and anything else extra before you do the calculations.

 

[robertdale]

Re: Am I over Propped?

the boat set since sept. it doesn't drain but around a glass of water after all day in the lake. it gets on plane easily and carries 3 adults and gear fine.

 

[Turkey]

Re: Am I over Propped?

I'm under propped on an 89 merc 150, wonder if we are compatible? I have a 21p ballistic ss splined on my 89 merc 150 small LU and I'm screaming it to 7000-7200 rpms @ 65mph with 2 people. I have a small hull, light weight, no jack plate, all though I have a friend dying to put one on it...it probably needs it. Right now I need more prop, the rest comes later. I am short on funds and looking for the best replacement option with the lowest price. I'm wanting a 24p 4 blade or a 25p 3 blade. But as long as I get better performance and a good price and I don't pop the motor or gear case, I'm willing to consider it as an option.

If we have compatible props (which I doubt) perhaps we could trade...mine needs work though...refurbishing here costs about 100 USD. Depending on the condition and compatibility perhaps we could come to an aggrement. The outboard specialists will know.

 

[kenmyfam]

Re: Am I over Propped?

the boat set since sept. it doesn't drain but around a glass of water after all day in the lake. it gets on plane easily and carries 3 adults and gear fine.

If it has soaked foam then it will only drain a glass of water. However if you think it is fine then only you can make the decision to rule it out.
On a boat that size your 150hp should perform as you say with twice the weight to push. Anyway i hope you get it sorted out.

 

[robertdale]

Re: Am I over Propped?

what do you do if the foam is soaked? what size prop comes factory or was standard on the 1989 150? the rpm is only a couple hundred lower when loaded down. does that sound normal?

 

[kenmyfam]

Re: Am I over Propped?

what do you do if the foam is soaked? what size prop comes factory or was standard on the 1989 150? the rpm is only a couple hundred lower when loaded down. does that sound normal?

The foam if it has any will be under the floor, and without ripping the floor out it is hard to tell. Thats why I suggested the "weigh it" thing as that is what i did and now I know my boat is O.K. Did you get a handbook for the motor when you bought it ?? standard prop would be in there.

 

[robertdale]

Re: Am I over Propped?

Re: Am I over Propped?

no book with the motor. if i try a prop that is slightly smaller and it revs better should that be the prob. i'll try to weigh the boat.

 

[kenmyfam]

Re: Am I over Propped?

Re: Am I over Propped?

no book with the motor. if i try a prop that is slightly smaller and it revs better should that be the prob. i'll try to weigh the boat.

Local outboard mechanic should be able to tell you the original prop. See if you can work with a prop shop to try out a few variations in pitch. Just have the courtesy to actually buy from them when you make a decision as to which one is for you. I have a couple of places around here that will do that for you. I am planning to try a couple more this summer. Just remember you are responsible for the prop while you test it.
Good Luck.

 

[robertdale]

Re: Am I over Propped?

Thanks for the advice.