Hole shot, Mercruiser 4.3L

[nola mike]

I think I *finally* have my engine dialed in decently enough to move on to the prop...

I have a Vortec 4.3L with an Edelbrock 1409 4bbl carb, supposedly should be around 220hp, but it doesn't seem that powerful. My jetting might not be perfect, and my intake might be hurting me a bit.

However, last season I had a standard black max 21p that topped out at 48 mph, maybe 4600 rpm? Don't remember exactly. Of course, I can't find the prop now to switch back LOL.

Switched out to a 19p michigan wheel. After tweaking a few things, I hit 46-47 mph today at 47-4800 rpm with me and my kid on board. It planes great, but had a hard time pulling me up on a slalom ;ast season (actually the 19p didn't feel any better than the 21p, and neither were a huge improvement over the 3.7L running the same 21p).

Was thinking a 4 blade might be better for skiing, but now I'm not sure. I'm pretty happy with the mid-range on this, the boat doesn't care much if I have 2 or 10 on board.

So what would be the next step? I was thinking turning point hustler 4 blade 21p. Tried a solas 4 blade 19p and the thing cavitated so bad when I hit it that I thought I spun the hub.

Boat isn't worth much, so can't justify $500 on a prop, especially if I don't know what the gain would be. Nobody nearby will demo props. Switching props in the water is a PITA, so not loving the idea of multiple props.

 

[Scott Danforth]

move your spotter and beer cooler to the bow for skiing. have drive completely down for the holeshot and as it starts climbing, thumb up on the trim

try that first

 

[nola mike]

move your spotter and beer cooler to the bow for skiing. have drive completely down for the holeshot and as it starts climbing, thumb up on the trim

try that first

That ain't it. I'm even leaving the cooler at the beach. Short double high wrap deep water start takes a lot of oomph. I can do it, but would like to not have a wall of spray in my face for 20 seconds. So wanting the ideal prop for that; I'm OK sacrificing top end, and don't want to be cruising at 30 mph @4k rpm.

 

[Scott Danforth]

That ain't it. I'm even leaving the cooler at the beach. Short double high wrap deep water start takes a lot of oomph. I can do it, but would like to not have a wall of spray in my face for 20 seconds. So wanting the ideal prop for that; I'm OK sacrificing top end, and don't want to be cruising at 30 mph @4k rpm.

Put the cooler in the bow, or 60# of weight like a sand bag.

 

[nola mike]

Put the cooler in the bow, or 60# of weight like a sand bag.

Spotter is already in the bow. I can tell you for sure that more weight in the boat doesn't help, regardless of where it is.

 

[tpenfield]

You can try a bunch of different props, but you probably want to stick with the one that matches your needs the best. Keep in mind that a prop that gets you the best top speed may not be very good for water sports.

I'd try the 4 blade . . . maybe even a 'HighFive' if you can find one. But at the end of the day, you'll have to decide on winning races or pulling up water skiers.

If you use the cooler in the bow (to balance the load), you may have to limit your water sports to earlier in the day. I find that coolers get much lighter as the day goes on

 

[Chris1956]

Propping that V6 for mid-40MPH will rob lots of power for slalom. I presume the boat is 18 foot plus.

I had a similar setup. I installed tabs. So tabs down, full power was better to start a skier, but not great. She also rode like a garbage scow with tabs down.

Run a 17P prop for slalom. 19/21 for cruising. Tabs likely cost too much for you.

I like the TP Hustlers in 3 blade. 4 blade will be fine as well, but you might want to decrease pitch a bit.

 

[Scott06]

I think I *finally* have my engine dialed in decently enough to move on to the prop...

I have a Vortec 4.3L with an Edelbrock 1409 4bbl carb, supposedly should be around 220hp, but it doesn't seem that powerful. My jetting might not be perfect, and my intake might be hurting me a bit.

However, last season I had a standard black max 21p that topped out at 48 mph, maybe 4600 rpm? Don't remember exactly. Of course, I can't find the prop now to switch back LOL.

Switched out to a 19p michigan wheel. After tweaking a few things, I hit 46-47 mph today at 47-4800 rpm with me and my kid on board. It planes great, but had a hard time pulling me up on a slalom ;ast season (actually the 19p didn't feel any better than the 21p, and neither were a huge improvement over the 3.7L running the same 21p).

Was thinking a 4 blade might be better for skiing, but now I'm not sure. I'm pretty happy with the mid-range on this, the boat doesn't care much if I have 2 or 10 on board.

So what would be the next step? I was thinking turning point hustler 4 blade 21p. Tried a solas 4 blade 19p and the thing cavitated so bad when I hit it that I thought I spun the hub.

Boat isn't worth much, so can't justify $500 on a prop, especially if I don't know what the gain would be. Nobody nearby will demo props. Switching props in the water is a PITA, so not loving the idea of multiple props.

In a similar situation with my old boat ( worse on power -3.0) i used Michigan vortex 4 blades 18” fir cruising, 16” fir skiing. saw better holeshot, sternlift and lower planning speed than with my 19”&17” three blades.
alternatively i bought all my ss props used off ebay. Took a couple years to find them but i dint pay more than $300

 

[jimmbo]

Even though I have been Chastised for saying this, I will do so again, a 4.3 is simply too small to use in a boat longer than 17ft, if water sports other than Wakeboarding are tried. Torque at low Rpms is too low, especially if they are trying to get more HP at the top end. Propping for skiing will certainly result in over revving when used otherwise. But short of Nitrous, you have little choice other than that to get more towing power.
You replaced the original engine with a 4.3, I am assuming the 4.3 came out of a Truck. Every Truck to Boat transplant I have ever seen, has shown to have poor Hole Shot, when compared to an actual Mercruiser/Volvo engine.

Intake design can certainly affect Low End Torque, Single Plane(Open Plenum) designs will produce a mushier Bottom End, but a couple of HP more at the Top.

 

[nola mike]

Even though I have been Chastised for saying this, I will do so again, a 4.3 is simply too small to use in a boat longer than 17ft, if water sports other than Wakeboarding are tried. Torque at low Rpms is too low, especially if they are trying to get more HP at the top end. Propping for skiing will certainly result in over revving when used otherwise. But short of Nitrous, you have little choice other than that to get more towing power.
You replaced the original engine with a 4.3, I am assuming the 4.3 came out of a Truck. Every Truck to Boat transplant I have ever seen, has shown to have poor Hole Shot, when compared to an actual Mercruiser/Volvo engine.

Intake design can certainly affect Low End Torque, Single Plane(Open Plenum) designs will produce a mushier Bottom End, but a couple of HP more at the Top.

The hole shot is actually fine, except when trying to get me out of the water. Boat loaded, no problem. Certainly this should have more power than the 3.7 that I replaced. Again, I may still have some HP on the table from the intake and carb that I need to investigate, but I'm close enough now that I don't think that there will be major changes.
Got off the phone with Solas re: the 19p 4 blade that was cavitating. He couldn't tell me if the thrust washer was the same as used on a QS fixed hub prop (though it should be). The lock washer broke when I took it off, but I'd like to give it another shot. I think that it *should* be an improvement.

 

[jimmbo]

The hole shot isn't fine if you can't pull a skier up. Torque, rather than HP is more critical for Hole Shot, Increases to top end HP, usually lower Low Rpm Torque.

 

[Scott Danforth]

Spotter is already in the bow. I can tell you for sure that more weight in the boat doesn't help, regardless of where it is.

Understanding leverage and fulcrums when pulling a skier with a butt heavy sterndrive

Try adding weight to the bow

I put 3 people in the bow of the Avanti with the anemic 3.0 to get my fat butt up. The weight forward of the fulcrum point of the hole helps counteract the load from the skier to get the boat and skier up faster

 

[QBhoy]

I’d urge you just to go get a good stainless merc prop. All the rest are simply a distant compromise. Well worth the money for sure.

 

[Scott06]

I’d urge you just to go get a good stainless merc prop. All the rest are simply a distant compromise. Well worth the money for sure.

Agreed. I bought mine used off ebay $300 was the most I paid for perfect condition props. Best prices are in January

 

[QBhoy]

Agreed. I bought mine used off ebay $300 was the most I paid for perfect condition props. Best prices are in January

Yeah. You can find good ones cheap enough, if you look for long enough. I just think anything else other than a merc prop, is just a waste of time. Nothing like the quality and finish they have.

 

[jimmbo]

Yeah. You can find good ones cheap enough, if you look for long enough. I just think anything else other than a merc prop, is just a waste of time. Nothing like the quality and finish they have.

You forgot to mention the Engineering that went into them too

 

[QBhoy]

You forgot to mention the Engineering that went into them too

Didn’t want to rattle on and bore people. But now you mention it…yeah, haha. You wouldn’t put cheap wheels and tyres off a honda, on your corvette, would you.

 

[Scott06]

The hole shot is actually fine, except when trying to get me out of the water. Boat loaded, no problem. Certainly this should have more power than the 3.7 that I replaced. Again, I may still have some HP on the table from the intake and carb that I need to investigate, but I'm close enough now that I don't think that there will be major changes.
Got off the phone with Solas re: the 19p 4 blade that was cavitating. He couldn't tell me if the thrust washer was the same as used on a QS fixed hub prop (though it should be). The lock washer broke when I took it off, but I'd like to give it another shot. I think that it *should* be an improvement.

Pretty sure the thrust washer between pressed hub and replaceable hub I believe is different.

If the 19" Michigan 3 blade worked reasonably well try an 18" michigan vortex 4 blade. I ran a two on my old boat (17 ft /3.0) 18" for tubing and cruising, 16" for skiing and boarding. I am pretty hefty and it would pull me right up ...I would think the 18" would be comprable to the 19" in WOT rpm perf but have better holeshot, stern lift and lower planning speed. If you don't mind swapping props try the 16" but you would over rev.

If you can find one try a merc vensura/offshore. I think on a lighter boat like yours that would work really well. I found one on ebay for $300 and had the best holeshot of any prop I tried (including high 5, Enertia, and Rev 4).

 

[nola mike]

Actually just realized I made a mistake in my OP. The bigger prop was actually 23p, and I've been using a Michigan 21p. The 4 blade was a 19p. All were fixed hub. I'm waiting on a new lock washer for the 4 blade, and needed a bigger socket than my 1 1/16 for the included brass nut. I think the thrust washers should be the same for all the fixed hub, but nobody seems to know for sure.