I have a 76 h30. I in the process of repowering and I will also have to reprop as my present prop is a LH 13x13, and my new engine will need a RH prop. My prop is very close to the strut and I have about 1.5" clearence between the prop and the bottom of the boat. I want to go to a larger prop and I think I can, with a new prop shaft, extend the prop further aft and increase the clearance. How much clearance do I need between the prop and hull? Thanks, Royce
- Status
You Do NOT have a choice on prop size.
Royce: You do not have a choice on prop sizing. It is a function of the engine horsepower, transmission ratio and tip clearance. If you try to cheat the system you will pay. Contact Bay Props in Alemeda Ca. Ask for Bob Kilian and talk to him about a prop. He will fix you up and you will be a happy sailor with a new engine and prop solution.
Royce: You do not have a choice on prop sizing. It is a function of the engine horsepower, transmission ratio and tip clearance. If you try to cheat the system you will pay. Contact Bay Props in Alemeda Ca. Ask for Bob Kilian and talk to him about a prop. He will fix you up and you will be a happy sailor with a new engine and prop solution.
repower/reprop
Royce-most of the time when you do this you will need to get a expert opion and let them run the calucations to see what will work best.Steve's idea is good advice.One suggestion I have if the clearance is tight consider a three blade prop if you need to go bigger,with a three blade you will still have the clearance between the hull and shaft (maybe even more then before as you might be able to go a 12 diameter prop). I'm thinking a 3 blade 12x14 or maybe 12x15 depending on how much more h.p. you add.The best answer is a good prop shop/repower expert.There is a rule of thumb for clearance between hull and prop(it is a % of the prop diameter?)Again a good prop shop will know.
Royce-most of the time when you do this you will need to get a expert opion and let them run the calucations to see what will work best.Steve's idea is good advice.One suggestion I have if the clearance is tight consider a three blade prop if you need to go bigger,with a three blade you will still have the clearance between the hull and shaft (maybe even more then before as you might be able to go a 12 diameter prop). I'm thinking a 3 blade 12x14 or maybe 12x15 depending on how much more h.p. you add.The best answer is a good prop shop/repower expert.There is a rule of thumb for clearance between hull and prop(it is a % of the prop diameter?)Again a good prop shop will know.
Repower/reprop
Royce-I reread you post and realized you were thinking of putting a longer shaft on to go with a bigger prop,check with the experts but I think this is a bad idea as it will change the equation for the prop/strut position, could cause vibration and or excess shaft wobble and cutlass bearing wear,would not suggest changing the prop shaft lenght.
Royce-I reread you post and realized you were thinking of putting a longer shaft on to go with a bigger prop,check with the experts but I think this is a bad idea as it will change the equation for the prop/strut position, could cause vibration and or excess shaft wobble and cutlass bearing wear,would not suggest changing the prop shaft lenght.
One thing that you may not realize
if you resize a prop, Royce, is that it can effect the efficiency of the engine. I had a marina put the wrong size (one size smaller) on my boat after a problem that bent the shaft and cracked the prop. Instead of ordering a new one the right size, they used one out of stock and pocketed the difference from my insurance company. The real problem was that I could not get the proper RPM's out of the engine. It built up heavy black smoke and covered my aft and starboard side of the boat with black crap. I spent over $500 trying to find the problem when I read about prop size issues. One of the experts on props was consulted and he gave me examples of issues with the wrong size prop. I couldn't believe how many of those issues fit my situation. Bottom line: had the right size prop delivered to the new marina, the boat pulled and the props switched. The result was IMMEDIATE, and we've had no problems since. BTW, the cost to haul and recommission was $120 and the new (right size) prop cost another $185. So, I have over $800 in charges due to incompetence and greed on the part of the Old marina. All this to say: Be Sure That You Know All The Potential Issues Before You Change Prop Size
if you resize a prop, Royce, is that it can effect the efficiency of the engine. I had a marina put the wrong size (one size smaller) on my boat after a problem that bent the shaft and cracked the prop. Instead of ordering a new one the right size, they used one out of stock and pocketed the difference from my insurance company. The real problem was that I could not get the proper RPM's out of the engine. It built up heavy black smoke and covered my aft and starboard side of the boat with black crap. I spent over $500 trying to find the problem when I read about prop size issues. One of the experts on props was consulted and he gave me examples of issues with the wrong size prop. I couldn't believe how many of those issues fit my situation. Bottom line: had the right size prop delivered to the new marina, the boat pulled and the props switched. The result was IMMEDIATE, and we've had no problems since. BTW, the cost to haul and recommission was $120 and the new (right size) prop cost another $185. So, I have over $800 in charges due to incompetence and greed on the part of the Old marina. All this to say: Be Sure That You Know All The Potential Issues Before You Change Prop Size
Checked my clearence
I checked my clearence and I cannot go to a larger dia. prop. I have a little over 1" clearence with the 13" prop. I'm going from a 12 hp engine to a 22hp. I'll be checking with some prop shops next week.
I checked my clearence and I cannot go to a larger dia. prop. I have a little over 1" clearence with the 13" prop. I'm going from a 12 hp engine to a 22hp. I'll be checking with some prop shops next week.
You need a minimum of...
10% of prop diameter for clearance else you risk excess vibration and prop tip ventilation. I don't think it would be prudent to put a bigger than 13" prop on a H30; a 14" leaves only 7% clearance. A too small prop presents no problems but a slow boat; smoke is likely from too high a pitch. The pitch number is how far forward a single turn of the prop would travel if it had no slip; a higher number means the boat is pushed further forward but requires more horsepower at a given RPM. A diesel smokes when it is trying to deliver more hp than it can; you can fix this with a lower pitch prop. Michigan Wheel makes the vast majority of props in the US and they are easy to talk to on the telephone. I put a 3 bladed 13" feathering prop on my H30. Expensive, but its the best solution. I adjusted the pitch until I could just make full RPM at full throttle. Putting a 3 bladed fixed prop on a swell sailing boat like an H30 is just a crying shame.
10% of prop diameter for clearance else you risk excess vibration and prop tip ventilation. I don't think it would be prudent to put a bigger than 13" prop on a H30; a 14" leaves only 7% clearance. A too small prop presents no problems but a slow boat; smoke is likely from too high a pitch. The pitch number is how far forward a single turn of the prop would travel if it had no slip; a higher number means the boat is pushed further forward but requires more horsepower at a given RPM. A diesel smokes when it is trying to deliver more hp than it can; you can fix this with a lower pitch prop. Michigan Wheel makes the vast majority of props in the US and they are easy to talk to on the telephone. I put a 3 bladed 13" feathering prop on my H30. Expensive, but its the best solution. I adjusted the pitch until I could just make full RPM at full throttle. Putting a 3 bladed fixed prop on a swell sailing boat like an H30 is just a crying shame.
3 blade fixed prop a shame?
Royce make your own decision (after getting a experts thoughts at prop shop)but you are talking thousands of dollars vs. hundreds of dollars for a feathering vs. fixed props. You need to make a honest evaluation of your boating use and budget.There is a minimal increse in drag from a fixed 3 blade vs. a fixed 2 blade (if sized correctly)think larger two blade/smaller three blade sq. inches of surface that "drag" when sailing. You will lose appx 1/4 to 1/2 knot under sail(worst case). How important is sailing speed vs. engine power and smothness ? How much do you use the engine? etc etc.You can always switch back to a 2 blade fixed if you are not happy and only be out a couple of hundred dollar vs. a couple of thousand for a feathering prop.I realize I may have gotten a little long but I took exception the the remark about it being a shame to put a three blade fixed prop on this boat.If you go with a larger hp. engine you need to match the prop or your will be overproped,this is just as bad (maybe worse) then being under proped.the three blade is a option to going with a larger two blade (that will not fit on you boat)There advantage to both,depending on your usage and needs. Good Luck!
Royce make your own decision (after getting a experts thoughts at prop shop)but you are talking thousands of dollars vs. hundreds of dollars for a feathering vs. fixed props. You need to make a honest evaluation of your boating use and budget.There is a minimal increse in drag from a fixed 3 blade vs. a fixed 2 blade (if sized correctly)think larger two blade/smaller three blade sq. inches of surface that "drag" when sailing. You will lose appx 1/4 to 1/2 knot under sail(worst case). How important is sailing speed vs. engine power and smothness ? How much do you use the engine? etc etc.You can always switch back to a 2 blade fixed if you are not happy and only be out a couple of hundred dollar vs. a couple of thousand for a feathering prop.I realize I may have gotten a little long but I took exception the the remark about it being a shame to put a three blade fixed prop on this boat.If you go with a larger hp. engine you need to match the prop or your will be overproped,this is just as bad (maybe worse) then being under proped.the three blade is a option to going with a larger two blade (that will not fit on you boat)There advantage to both,depending on your usage and needs. Good Luck!
You do have a choice!
Royce, I agree with Pete's comments about the choice of props. Also, you do have a choice of prop size. Even though you may not be able to increase diameter you will be able to size the pitch for optimum performance. Of course the best advice will be from a good local prop shop. You may want to get the opinion of size from at least two shops.
Royce, I agree with Pete's comments about the choice of props. Also, you do have a choice of prop size. Even though you may not be able to increase diameter you will be able to size the pitch for optimum performance. Of course the best advice will be from a good local prop shop. You may want to get the opinion of size from at least two shops.
A crying shame
Just for my perspective, I had a slip that required backing 270 degrees of a circle in reverse to get in. The two blade prop backed like a drunk. I swapped out for a 3 blade fixed and it backed somewhat better; there was little if any perceivable improvement in forward, certainly not top speed. I imagine there may have been some motoring upwind but it was small at best; this is consistent with what prop guys will tell you. *BUT* I absolutely saw an increase in drag under sail; I went from rarely being passed by anyone to working hard just to keep up. Prop people will say 3/4 of a knot or more; PHRF adds 12 seconds per mile for a fixed 3 blade prop. In my mind, this is a lot of lost speed. Finally, I got a feathering 3 blade at a cost of $1050 vs. $250 for the 2 blade vs. $300 for the 3 blade fixed. Due to the independently adjusting forward and reverse pitch, the reverse performance is outstanding compared to any fixed prop; powering forward is quite similiar to the others. Under sail, is the true reward; the joy of embarrassing bigger, newer, more expensive boats cannot be surpassed. Just my take; the important thing is get out there.
Just for my perspective, I had a slip that required backing 270 degrees of a circle in reverse to get in. The two blade prop backed like a drunk. I swapped out for a 3 blade fixed and it backed somewhat better; there was little if any perceivable improvement in forward, certainly not top speed. I imagine there may have been some motoring upwind but it was small at best; this is consistent with what prop guys will tell you. *BUT* I absolutely saw an increase in drag under sail; I went from rarely being passed by anyone to working hard just to keep up. Prop people will say 3/4 of a knot or more; PHRF adds 12 seconds per mile for a fixed 3 blade prop. In my mind, this is a lot of lost speed. Finally, I got a feathering 3 blade at a cost of $1050 vs. $250 for the 2 blade vs. $300 for the 3 blade fixed. Due to the independently adjusting forward and reverse pitch, the reverse performance is outstanding compared to any fixed prop; powering forward is quite similiar to the others. Under sail, is the true reward; the joy of embarrassing bigger, newer, more expensive boats cannot be surpassed. Just my take; the important thing is get out there.
Vetus
I found a 1987 Vetus m310 (22hp) 3 cyclinder that the guy purchased new in 1987 and never used or ran. It was still wrapped in the shipping plastic. I purchased it for $2800, (came with some extras too) and have ran it in my garage. It LOOKS brand new. I'll have it installed in a few weeks and I'll post how it went. I'm in the process of cleaning and painting my engine "room" now and taking care of some things while the engine is out. I'm doing this all in the water. The prop shaft is out and plugged.
I found a 1987 Vetus m310 (22hp) 3 cyclinder that the guy purchased new in 1987 and never used or ran. It was still wrapped in the shipping plastic. I purchased it for $2800, (came with some extras too) and have ran it in my garage. It LOOKS brand new. I'll have it installed in a few weeks and I'll post how it went. I'm in the process of cleaning and painting my engine "room" now and taking care of some things while the engine is out. I'm doing this all in the water. The prop shaft is out and plugged.
Sounds good
Why can't I find something like that
I've been hoping to find a new engine in someones barn for months now....... Oh well, good for you.
Why can't I find something like that
I've been hoping to find a new engine in someones barn for months now....... Oh well, good for you.- Status