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Author Topic:   CMC PT-35

dg22 posted 08-25-2010 11:42 AM ET (US)
What is the maximum weight of motor that you can use with the CMC PT-35? I know they say 35hp max. My motor is a 1972 Evinrude 50hp, 189 lbs. Is that too much weight and thrust for this unit?
My boat is a 1967 13 footer so I like that the PT-35 is very light (24 lbs) compared to the PT-130 (40 lbs), the next model up.

Tohsgib posted 08-25-2010 11:53 AM ET (US)
Not weight more than width. The PT35 only takes small engines with turn screws, etc. Your 50hp has the same mounting bracket as a modern engine correct? It will be too wide and you would not be able to bolt it up. Read the specs and I think the PT35 is only 11" wide and you need like 13.
Tohsgib posted 08-25-2010 12:00 PM ET (US)
Just whipped out my 72 brochure and your engine does have turn screws and weighs 187lbs. Should work if width is OK.
dg22 posted 08-25-2010 12:00 PM ET (US)
My motor actually has the thumb turn screws and I thought I did measure it to fit the 11" width but will double check that again this weekend.
dg22 posted 08-30-2010 10:24 AM ET (US)
Tohsgib, I checked the measurement and the motor bracket is 10" across and about 10 1/2" across the thumb screw washers. On the back, the bracket does bubble out where the top transom bolts go and that measurement is about 11 inches. So I'm thinking it should work. Do you think my boat will perform better overall with PT even though I'm adding 24 lbs to the back. Right now it runs great with a person up front but does porpoise a bit with me alone at lower speeds. I have the tilt pin set at the 2nd highest hole so the cavitation plate is level with the bottom of the boat.
Dave

Tohsgib posted 08-30-2010 10:52 AM ET (US)
Actually it will perform better and yes they will porpoise when level. If you notice most 13's are tucked in when running....design quirk.
pglein posted 08-31-2010 02:56 PM ET (US)
I would be concered about the force of the thrust acting on the hydraulic ram and the leverage effect on the transom more than I would about whether it will fit or the weight.
I have the same bracket and it visibly flexes about 1/2" when I throttle up my 30hp engine.
Tohsgib posted 08-31-2010 03:00 PM ET (US)
Probably why they rate it at 35HP. His 50 is more like a 40 so it might not be a problem.
tjxtreme posted 08-31-2010 05:02 PM ET (US)
I think they use the same hydraulic ram on the larger model, so that wouldn't be a problem.
dg22 posted 08-31-2010 05:27 PM ET (US)
I read a review on basspro of a guy breaking the lower bracket that holds the piston 3 times and this is with a 25hp Johnson. He says the aluminum brackets are just too weak. The other reviews are all positive so did this guy just get a bad one.
If pglein says the bracket flexes about 1/2" with a 30HP than maybe my motor will be too much. Is that normal for the unit to flex like that?
Tohsgib posted 08-31-2010 10:25 PM ET (US)
My PT130 was VERY tough with a 40hp OMC...I can't imagine a 25 hurting a PT35 but what do I know about them?
Tadpole posted 09-01-2010 09:24 AM ET (US)
1/2" of flex would really worry me; maybe his transom is flexing some? I think I remember that there are two pieces that mount to the transom independent of one another; of course they are bolted - at pivot point - to the piece on which the engine mounts. Anyway, I've had a 30 hp Yami twin (about 120 lbs.) on a PT35 for more than 5 years, I use it as hard as I please, and I have nothing negative to say about it - NO flex. In fact, I think it's either 5/16" or 3/8" thick aluminum, which is not flimsy. That said, it would be wise to proceed with caution if one is to exceed capacities given by manufacture/engineers.
You'd probably be okay, but maybe the decision is not completely unlike buying a trailer hitch, or a tow vehicle that's right at the very limit...hmmm.
dg22 posted 09-01-2010 10:33 AM ET (US)
I agree with Tohsgib that my 1972 50hp is more like a 40hp but possibly CMC has engineered this for a max of 35hp motors of the past (2-strokes) which would be more like a 25hp of today. I appreciate the feedback. I think I'll talk with CMC but wanted to get some feedback first. Thanks.
Jet Wrench posted 09-07-2010 06:49 AM ET (US)
I have a CMC PT-135. This is a stout unit! My motor weighs in about 225 (75 Johnson 70HP). I would contact CMC to check the maximum weight allowed for the PT-35. I would think you are OK. You will notice much improved performance with the CMC. The motor sits back about 5-6 inches, keeping you away from the turbulence. Here is a picture of the mounting for mine. At full throttle I can get my 66 up to 38 MPH at 5500 RPM, starts to plane at 3500 RPM.
http://picasaweb.google.com/lh/photo/C8Z9ZpFdKG_RIeLtfuSyqp0nldRknBxFq03FmBp6U5Q?feat=directlink
Jet Wrench
pglein posted 09-16-2010 12:35 AM ET (US)
You guys keep talking about the weight like it's the critical factor. IT'S NOT. If it was, they would have labeled it "for engines up to xxx pounds", not "for engines up to xx horsepower".
Think about it: The bracket is engineered to withstand up to a certain amount of force applied to it. This force is a combination of static weight and thrust from the propeller. When you put the engine in gear and throttle it up, the static weight does not go away. The thrust is simply ADDED to it. Common sense says that the force applied to the bracket from thrust dwarfs that that is applied from the static weight of the engine itself. Thus, the critical factor is how much thrust the engine produces. This is no less or more simple because the engine is a four or two stroke.
Looking at my PT-35, there is no doubt that, from a pure strength standpoint, it would easily hold my 150hp V6 Johnson. Does that mean it would work under load when the engine was in gear? Hell no! It'd snap like a twig.
Will it safely accomodate a 50hp? Maybe. But that is 42% more strain on the device than it was designed to withstand. How anyone could suggest that this is a risk worth taking is beyond me.
Tohsgib posted 09-16-2010 11:03 AM ET (US)
Could also be that engines over 35hp have the modern transom mount and won't fit. The ram is the same on this as the 130, I can't see how it would snap or even flex with a few added ponies.

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Author	Topic: CMC PT-35
dg22	posted 08-25-2010 11:42 AM ET (US) What is the maximum weight of motor that you can use with the CMC PT-35? I know they say 35hp max. My motor is a 1972 Evinrude 50hp, 189 lbs. Is that too much weight and thrust for this unit? My boat is a 1967 13 footer so I like that the PT-35 is very light (24 lbs) compared to the PT-130 (40 lbs), the next model up.
Tohsgib	posted 08-25-2010 11:53 AM ET (US) Not weight more than width. The PT35 only takes small engines with turn screws, etc. Your 50hp has the same mounting bracket as a modern engine correct? It will be too wide and you would not be able to bolt it up. Read the specs and I think the PT35 is only 11" wide and you need like 13.
Tohsgib	posted 08-25-2010 12:00 PM ET (US) Just whipped out my 72 brochure and your engine does have turn screws and weighs 187lbs. Should work if width is OK.
dg22	posted 08-25-2010 12:00 PM ET (US) My motor actually has the thumb turn screws and I thought I did measure it to fit the 11" width but will double check that again this weekend.
dg22	posted 08-30-2010 10:24 AM ET (US) Tohsgib, I checked the measurement and the motor bracket is 10" across and about 10 1/2" across the thumb screw washers. On the back, the bracket does bubble out where the top transom bolts go and that measurement is about 11 inches. So I'm thinking it should work. Do you think my boat will perform better overall with PT even though I'm adding 24 lbs to the back. Right now it runs great with a person up front but does porpoise a bit with me alone at lower speeds. I have the tilt pin set at the 2nd highest hole so the cavitation plate is level with the bottom of the boat. Dave
Tohsgib	posted 08-30-2010 10:52 AM ET (US) Actually it will perform better and yes they will porpoise when level. If you notice most 13's are tucked in when running....design quirk.
pglein	posted 08-31-2010 02:56 PM ET (US) I would be concered about the force of the thrust acting on the hydraulic ram and the leverage effect on the transom more than I would about whether it will fit or the weight. I have the same bracket and it visibly flexes about 1/2" when I throttle up my 30hp engine.
Tohsgib	posted 08-31-2010 03:00 PM ET (US) Probably why they rate it at 35HP. His 50 is more like a 40 so it might not be a problem.
tjxtreme	posted 08-31-2010 05:02 PM ET (US) I think they use the same hydraulic ram on the larger model, so that wouldn't be a problem.
dg22	posted 08-31-2010 05:27 PM ET (US) I read a review on basspro of a guy breaking the lower bracket that holds the piston 3 times and this is with a 25hp Johnson. He says the aluminum brackets are just too weak. The other reviews are all positive so did this guy just get a bad one. If pglein says the bracket flexes about 1/2" with a 30HP than maybe my motor will be too much. Is that normal for the unit to flex like that?
Tohsgib	posted 08-31-2010 10:25 PM ET (US) My PT130 was VERY tough with a 40hp OMC...I can't imagine a 25 hurting a PT35 but what do I know about them?
Tadpole	posted 09-01-2010 09:24 AM ET (US) 1/2" of flex would really worry me; maybe his transom is flexing some? I think I remember that there are two pieces that mount to the transom independent of one another; of course they are bolted - at pivot point - to the piece on which the engine mounts. Anyway, I've had a 30 hp Yami twin (about 120 lbs.) on a PT35 for more than 5 years, I use it as hard as I please, and I have nothing negative to say about it - NO flex. In fact, I think it's either 5/16" or 3/8" thick aluminum, which is not flimsy. That said, it would be wise to proceed with caution if one is to exceed capacities given by manufacture/engineers. You'd probably be okay, but maybe the decision is not completely unlike buying a trailer hitch, or a tow vehicle that's right at the very limit...hmmm.
dg22	posted 09-01-2010 10:33 AM ET (US) I agree with Tohsgib that my 1972 50hp is more like a 40hp but possibly CMC has engineered this for a max of 35hp motors of the past (2-strokes) which would be more like a 25hp of today. I appreciate the feedback. I think I'll talk with CMC but wanted to get some feedback first. Thanks.
Jet Wrench	posted 09-07-2010 06:49 AM ET (US) I have a CMC PT-135. This is a stout unit! My motor weighs in about 225 (75 Johnson 70HP). I would contact CMC to check the maximum weight allowed for the PT-35. I would think you are OK. You will notice much improved performance with the CMC. The motor sits back about 5-6 inches, keeping you away from the turbulence. Here is a picture of the mounting for mine. At full throttle I can get my 66 up to 38 MPH at 5500 RPM, starts to plane at 3500 RPM. http://picasaweb.google.com/lh/photo/C8Z9ZpFdKG_RIeLtfuSyqp0nldRknBxFq03FmBp6U5Q?feat=directlink Jet Wrench
pglein	posted 09-16-2010 12:35 AM ET (US) You guys keep talking about the weight like it's the critical factor. IT'S NOT. If it was, they would have labeled it "for engines up to xxx pounds", not "for engines up to xx horsepower". Think about it: The bracket is engineered to withstand up to a certain amount of force applied to it. This force is a combination of static weight and thrust from the propeller. When you put the engine in gear and throttle it up, the static weight does not go away. The thrust is simply ADDED to it. Common sense says that the force applied to the bracket from thrust dwarfs that that is applied from the static weight of the engine itself. Thus, the critical factor is how much thrust the engine produces. This is no less or more simple because the engine is a four or two stroke. Looking at my PT-35, there is no doubt that, from a pure strength standpoint, it would easily hold my 150hp V6 Johnson. Does that mean it would work under load when the engine was in gear? Hell no! It'd snap like a twig. Will it safely accomodate a 50hp? Maybe. But that is 42% more strain on the device than it was designed to withstand. How anyone could suggest that this is a risk worth taking is beyond me.
Tohsgib	posted 09-16-2010 11:03 AM ET (US) Could also be that engines over 35hp have the modern transom mount and won't fit. The ram is the same on this as the 130, I can't see how it would snap or even flex with a few added ponies.