Do I have any prop options. 12 foot aluminum

[searsfisher]

Ive got a 12 foot aluminum boat with an evinrude 5.5 fisherman. It barely pushes the boat. I think it's got the stock weed prop on it (8x7.25?). I think it sounds below the Rec range. It revs a fair amount higher in neutral, which I understand is Normal anyways.
I've tried different load outs with kids in front etc but it's never really able to get on plane at all. I'd think that a lower pitch prop would help but not sure what options I have. I don't expect a speedster but I know when I had a 6.5 on this years ago it had no problem.

The only other issue I am concerned about is the shaft length. It's a 15 inch transom but I measure about 17 inches to the cav plate which concerns me. I bought it as a short shaft and it looked it.

So will a prop help or do I need to pick up a motor with a shorter shaft?

 

[Sea Rider]

Welcome to Iboats,

When OB sits fully vertical on transom, is there prop aeration at full throttle ? If so, OB sits too high.

A 5.5 HP-OB is a very under powered OB for a 12 footer which has great hull drag to overcome fast compared to a higher HP-OB with higher hole shot. Worse if boating with added load than solo. That combo is only god for boring fast displacement speed. Get at least a 10 HP-OB to have fun.

Happy Boating

 

[jimmbo]

Stock prop was a 2 blade 8 X 7 1/4. Michigan did at one time make a 3 blade 7 3/4 X 6 1/2 for that engine. But even on a 10 foot car topper the 5.5 was just able to plane, except in the early morning and late evening when it was colder, then the thing went like the blazes

 

[searsfisher]

I can understand it having a hard time with me alone and a fuel tank back there so I was just hoping for something with a little less pitch. I wondered if that shaft length was pushing too much water though too.

I have no cavitation issues at all. And my old hull tag says a 9horse is max so would a 9.9 or 9.5 technically still be allowed? I'm not opposed to picking up a new toy

 

[Sea Rider]

Would dare say that there's a huge water drag going on at lower leg, water flow is not being cut at the lower edge located right under upper splash plate, it's banging at the non edge right over splash plate. will keep on banging & dragging untill a different HP-OB is used for the hull to get out of the hole fast and ride parallel to water level.

Check if a 3 blade alum prop with less pitch is available to better hole shot, or get a minimum 9.8 HP-OB, with a maximized prop should plane combo out of the hole. If plan boating with more souls go for a 9.9 or 15 HP-OB's, both weights same. 2 strokes are much lighter than their 4 strokes counterparts.

Happy Boating

 

[flyingscott]

A bigger outboard is probably not going to help you. I had a similar set-up with a 5.5 hp johnson on it i put a 15 hp on it which was way overpowered and made no difference. The problem is the older hulls are so narrow they don't carry weight well. What happens if you move to the front of the boat does it start to plane out that way.

 

[Sea Rider]

If under powered OB's are not revving towards max wot rpm range with a maximized prop will not achieve a fast hole shot, much worse with added weight, add hull & lower leg drag, bad weight distribution along badly trimmed. A boating disaster & frustration.

Happy Boating

 

[searsfisher]

So the problem is helped slightly if I stretch out toward the middle bench. I searched around for one of the 3 blade props but had no luck at all. So to hopefully rectify my issue I picked up a 3 blade prop attached to a '64 evinrude 9.5. So onto a couple minor issues with this motor surging a little at WOT but pushing the boat along very well already. I will be doing some searching for this issue in other thread sections. Thanks much for the advice from all of you.