Change prop or bigger motor?

I have little to no knowledge of boat motors so I thought I would ask this question. I have a skeeter tiller that is rated for a 75 horse motor. Right now I have a two year old 70 horse 4 stroke on it. It takes quite a while to get to plane when I have a few other people in the boat or when I have water in my rear livewell. I have heard that changing the prop could work but would reduce my top speed? I really don’t care how fast I go… Or should I look at getting a 75 horse? That being said should I get a 2 stroke or a 4 stroke? I heard something about the 4 strokes getting their power from high rpm’s and that is why it takes my boat so long to plane but I have no idea. Any help from the gallery? Thanks in advance.

Like a lot of other prop questions, my usual response is same as below:

Mocha wrote:

This sounds like a situation for Ricky the “Prop” man in Brainerd MN. Give the guy a call. He has done wonders with advise and the correct props. IMHO

X2

Really set me up with an incredible prop.

http://www.in-depthoutdoors.com/community/forums/topic/1675-impact-prop-selection/

If you’re looking for the best bang for the buck, I would say a spitfire 4 blade aluminum prop in the same pitch you run now would get you way better hole shot and on plane faster, with very little top end loss. Since you run a yamaha, you’d also need to get the Mercury Flo Torque Hub system for your Yamy (about $50). You won’t see much difference between that 70 and 75, especially since the 70 is so much lighter.

wimwuen wrote:

If you’re looking for the best bang for the buck, I would say a spitfire 4 blade aluminum prop in the same pitch you run now would get you way better hole shot and on plane faster, with very little top end loss. Since you run a yamaha, you’d also need to get the Mercury Flo Torque Hub system for your Yamy (about $50). You won’t see much difference between that 70 and 75, especially since the 70 is so much lighter.

There is no guarantee that the current prop pitch is correct. One has to do a WOT RPM test to see if the prop is close to being right. Changing a prop pitch by a couple inches usually doesn’t effect the top end by more than 2 – 3 mph. Jeffrey, the good news is that this is definitively a prop issue and not a motor change.

SuperDave1959 wrote:

the good news is that this is definitively a prop issue and not a motor change.

Now that is a relief! Thanks everyone!

I don’t think going from a 70 to a 75HP will help you much at all. Curious what model Skeeter you have that’s only rated for a 75HP motor? There was a time that 4 stroke motors did not have the same holeshot power as a same size 2 stroke motor. I’m not sure that is the case in modern 4 stroke motor.

I think it is an s-135? It is a 1993 boat. It weighs right around 1000 pounds.

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Drop the pitch and increase hole shot but decrease top end.
Likely you’ll see your wot rpm higher than when running higher pitch. Beware of over rev.

The hole shot on my boat and top end are noticeably different when switching between a 15 & 17 pitch.

I prefer the hole shot to the speed but last week I destroyed my 15 so this week my boat is faster but slow out the hole

Jeffrey Trapp wrote:

I think it is an s-135? It is a 1993 boat. It weighs right around 1000 pounds.

I had that Skeeter model in ’93 new (won a PWT championship in the model 135) Top end, with 2-3 people and a load of gas etc. will be around 32 mph.–tops–light load maybe 35 mph. The 2-strokes are always a little faster on top end and will idle at a lower RPM. as well –than the 4 strokes–only louder –IMO. That said, a stainless prop will make a big difference for you I think. I had a 93 Merc with a 3 blade stainless ( I can not recall pitch)on mine ( the 135) and that boat was as fast or faster than any of the tillers I owned in that model/size. of boat over the years. The engine should be mounted about one hole higher than the norm if I recall right. The Skeeter factory should have still have specs on that boat available with a phone call to—maybe the R and D. dept.?

Years ago–Frankies Marine in Chisago City, MN. sold lots of those model 135’s and if you talk to Frankie Jr., he might be able to answer your questions as well. ( use my name as reference if need be)

BEST riding hull I ever owned in that size range for BIG water …

Edit–a stainless “high five” will get you a better hole shot–but slower top end speed. The high five will also troll forward slower–but harder to grab water in reverse.

The reason I say to try the same pitch on that spitfire is that it’s typically a slightly smaller diameter than the 3 blades. It’s been my experience that it is most commonly the same diameter as the original 3 blades when it comes to the spitfires. You are right though, you might have to drop a pitch if you’re not getting the RPMs you need.

I absolutely love the boat. You are right about the big water! My first weekend with it I was out on Oahe and the wind came up. I came out of a bay and boy was I happy with that boat. It handles awesome.

I’ve been through this in a different but similar boat and think Steve’s advice is spot on. It’s hard to say how a 75 would perform compared to your 70. With that said, I think the advice about trying a different prop is right on unless you want a new motor.

Find out what your max RPMs are for your motor, and find out what your WOT RPMs are with the current prop. Assuming there is a gap of at least 200 RPMs between the current WOT RPMs and your max, the easiest thing to do is try the same prop in the next lowest pitch.

If this doesn’t work or you eventually decide to repower, I would encourage you to get the most cylinders and displacement you can in a 75. Talk with people about specifics (gear ratio can matter a lot) but a 4 cylinder vs a 3 cylinder usually leads to more torque on the low end to get you on plane fast.

No matter what you do—the fact is those hull/engine combos will be slow/sluggish onto plane with a load of people etc. That said, an added “hydrofoil” will help the hole shot/onto plane and might be the easiest/cheapest to test. “Doel Fin” or the like…??

Keep in mind-all this prop talk and hole shot vs. top end speed-yes, a better hole shot will probably drop your top end, but you’re talking a difference of a couple to a few MPH. This may matter to a tourney guy or racer, but…I’ve never been outrun by a fish, even in my old 16′ jon boat/9.9 hp days.

You need to accurately find out what rpm you are at at empty wot and fully loaded wot. Only when you know that can you speak to a prop guy to get the right pitch. over or under pitch can ruin a motor. You want to be closest to your highest recommended rpm by the Motor manufacturer. Just say I know from experience.

Mwal

Thanks guys!

One more question for those that know…

If I have a 3-blade, 19P prop and I go to a 4-blade 19P prop, what happens? Is there a difference? My guess would be a bit slower due to the increase in mass, but tell me.

Each boat will react a bit different but here is what happened when I started playing with mine. Boat is a full console so not apples comparison but I have a 90 hp 4stroke. Came with a 13x19p on it that was painfully slow out of the hole. Tried a 4 blade spitfire 13.25x17p and boat all but jumps out of the water with very little loss of top end. Get closer to wot rpms but still not hitting 5500. I picked up a 3 blade 13.75x17p I plan to try and see if I maybe gain some top end and still have good holeshot.

PROP, absolutely do not go for a new motor unless you WANT A NEW MOTOR. 5hp….. NOTHING…! Your so close to the full HP its rated for I wouldn’t even think about it. Drop a few pitch sizes to get more hole shot with less top end. Is your current prop all nicked up? That will make a big difference.