1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

[ShawnQ]

I am just about to buy a Chrysler boat, v-bottom glass hull. It currently has a 70hp Johnson (1976 I believe) and it isn't running correctly.<br /><br />I have a line on a 125hp for a really good price, would this be overkill for my boat?\<br /><br />Any tips or guidelines would be helpful. I can get the serial #'s, etc, off of the boat if the need be.<br /><br />Thanks!<br />Shawn

 

[boatingfool]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

Is there a placard somwhere inside the boat that has a US Coast Gaurd max H.P. rating??

 

[Parrott_head]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

For a point of referance, I use to own a Glastron 156C TriHull. The name plate rating on it was 85HP max. The boat had a 75 HP motor on it and performed well with it. Could pull two skiers if they were good skiers. If this Chrysler boat is a tri hull I'm sure it would be similar. Not sure how a V-Hull configuration would change the equation. <br />Be aware that you can assume legal liabilities if you put more motor on a boat then it was certified to handle.<br /><br />There should be a rating plate somewhere near the helm of the boat. Mine had one and it was a 1975 model boat.<br /><br />Here is a website that has a sales brochure for 1979 models posted. http://www.hurrikain.com/thechryslercrew/79-scans.htm <br /><br />They do not list a V-hull configuration in the 15 foot range. If you will scroll down a bit you will find Spec and Options chart that lists maximum hp for each model of boat.

 

[ShawnQ]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

I didn't really get a chance to look for one. It was dark and I was too excited to think of it.<br /><br />However, I just picked up the boat, and paid in full for it (all of $500, hehe). So it's mine now!<br /><br />I am going to look for the tag tomorrow.<br /><br />Anyone else have any recommendations?<br /><br />Thanks!<br />Shawn

 

[Solittle]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

Give some thought to getting the 70 running. I suspect the 125 would be way over the max for your boat from both a safety and weight standpoint.

 

[Terry H]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

Shawn...I had a similar boat years ago that had a 70hp Chrysler on it...would get up to almost 40mph. The boat was rated for 90 hp. I wouldn't think 125hp would be safe...mostly too much weight...just a Thought

 

[scotiany]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

This is quite a general reply but, I've got a '70 14' 6" runabout and the max HP is 55.

 

[ShawnQ]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

Well guys, <br /><br />The boat I bought (that's a tongue twister) is a 1968 Chrysler Commando 151. I went to a website called 'The chrysler crew', and they had scans of the original brochure for my boat, awesome! It said it will hold 5 or more (I would only fish 4), and it is rated at 90hp max. <br />Back then, H.P. was rated at the engine, where as now it is at the prop. So, if I went with a newer engine, an 80 would be about right (~10% loss on older engines).<br /><br />Thanks for the help! Great site!<br /><br />Shawn

 

[what200]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

The CG formula only accounts for the dimensions of the boat and has little to with actual power handling characteristic of a boat. It greatest use is to give insurance companies an excuse to deny coverage.<br /><br />I have a 17' aluminum runabout/fishing boat that is rated for 100 and have a 150 on it and runs right up to 54 safely. I have a boating buddy down the road from me that has a Mercury bridgeport (245hp) on a 15' hydrostream and his is safe enough. Some may shoot me down for this but I just happen to think that safety has more to do with the operator than the boat.<br /><br />So if you don't mind the liability and she'll float it, slap the 4 cyl mopar on there and let her rip. I doubt you'll get much past 50 anyway.

 

[JB]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

The operator has nothing to do with the torque and thrust placed on a transom, What200, or the vibrations transmitted to the hull.<br /><br />You may defy fate on your own, but it is not a good idea to tell others it is safe.

 

[f_inscreenname]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

Not saying a word. <br />Hum to hum,hum more power hum hum hummmmm...<br /><br />p.s. The 115 would only be fun on a lake as smooth as glass.

 

[what200]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

You'll notice I didn't say that doing so is risk free, but anyone who wants a risk free hobby had better move tampa and join a shuffle board league. I was just giving an opposing point of view that boats can be overpowered, but maybe I should have given more info. On my overpowered boat, I backed the transom with 1/2" aluminum plate and tied the top of the transom to the stringers with 1/4" steel cable.<br />Maybe his needs reinforcement or maybe not. Maybe his transom is rotted crap and a 50hp motor will send it to the bottom. I think on an internet board there is much that we have to assume and I usually assume people have common sense. Sometimes I'm wrong but usually not.<br /><br />Happy boating.

 

[Franki]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

I have a 17 + foot half cabin, and although it has no plate to tell me its rating,, the general concensus was that it was probably rated to about 80HP...<br /><br />I currently have a 100HP Johnson on the boat and I defy anyone to tell me its unsafe... <br />Here are my reasons:<br /><br />1. The Johnson 80 and 100 of that vintage were essentialy the same engine. (very similiar weight, I can say this with some authority since I have one of each sitting behind my house.)<br /><br />2. This boat is built like a brick sh!thouse, thickest fiberglass I've ever seen.<br /><br />3. the stringers, I reinforced with massive Jarrah beams running the length of the hull. (I toyed with converting to inboard at one stage and then changed my mind, but left the beams there.)<br /><br />4. This thing has a huge very thick very strong outboard well. I can sit on top of the 100HP with my 120KG and the transom doesn't flex at all. (that's with the boat on the trailer.)<br /><br />5. I have yet to put it to wide open throttle, but at about 3/4 throttle, its not straining at all, much better then my old motor which had to work pretty hard to get to my cruzing speed..<br /><br />6. This engine is pretty old, its probably only putting out 90-95% of its original rating (if that).. and since its the same weight as the 80 would have been, there is not much in it.<br /><br />7. There is no liability that I am aware of in Australia with regards to engine size.. you can put a V8 in a dingy if the urge takes you. (and if you are dumb enough to try. <br /><br />So taking all that into account.. the main points for you are the liability issue, and looking at your boat logically and determining if its strong enough to handle it, and also if it doesn't adversly affect her handling...<br /><br />The difference in weight is what??? 30 KG max I would guess and probably somewhat less ??? I syspect that the torque force and vibration on the transom is more of an issue then the weight. perhaps you could get an engineer to check it out and have it certified above its original rating if she merrits it...<br /><br />by the same token, if it doesn't make alot of difference in speed, it probably will in fuel cost.. maybe that should be a consideration.<br /><br />regards<br /><br />Frank

 

[Capt Ron]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

You can figure out the recomended motor size by going to: <br /><br /> http://www.uscg.mil/d8/mso/louisville/download.htm <br /><br />and reading the publication: <br /><br />Safety Standards for Backyard Boat Builders <br /><br />It has easy to follow details to give you the answer that you seek.<br /><br />Capt Ron

 

[SeaMasterZ@aol.com]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

thats exactly right franki, within reason and constantly within reasonable limits<br /><br />nope, a 125 on a dingy wont float, wont go anywhere but straight to the bottom<br /><br />CONVERSELY ...<br /><br />too SMALL a motor on a boat can be a liability as well<br /><br />and lets be real, sometimes you get into TROUBLE ... middle of the night, a pop up thunderstorm, no forecast, not in the computer models, but WTF is this, its coming in right on top of us --- if feasible, if the waves arent too bad yet, its good, DAMNN GOOD to have a little extra grunt back there<br /><br />buddy of mine had his pride and joy out, 200 horse Black Max on an 18 foot Robalo, down brandywine, and we are doing well, big tiderunners, omg ... <br /><br />then the sky changed, stars wernt out<br /><br />they call for storms tonight?<br /><br />nope, clear thru all the next day<br /><br />these fish are sure biting .., that u sually means storm ...<br /><br />Lighting bolt over Delaware ...<br /><br />lines in, fired up, GONE ... its a long way up to fortesque, but old Maximillion blasted us up there in record time, Robalo slicing most waves and launching off a few, but at a mile a minute the bay shrinks ... we didnt beat the rain, but boat on trailer, engine flushed and us safe in the cab before the lighting hit Spectacular show, but damnn glad to be watching it, not IN it<br /><br />legally overpowered? yeah ...<br /><br />realistically overpowered? ... helll no, DANGEROUS would be having some 20 horse slug out there, droning our way thru the waves and lighting and hail of the storm that CERTAINLY would have nailed us<br /><br />Motors are dumb - sure the newer ones have computers that can think serially faster than we can, but OUR grey box is massively parallel, and takes in millions of variables every second<br /><br />pay attention, and you dont get hurt<br /><br />layer your self with a few dozen GUIDO chains, guzzle a few gallons of beer and plant those throttles into the firewall of your twin 275 horse puddle jumper, and yeah, likely youre gonna be a statistic <br /><br />be smart<br /><br />not dead

 

[tradin]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

i have a 16 ft chrysler with a merc 85 on it my tag says max engine 115 hp go from there

 

[andrewkafp]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

I personally think that's it's a good practice to follow the guidelines of the manufacturers and marine engineers.<br />If modifications can be made without compromise to safety then go ahead and do it.<br />Perhaps a 125hp motor is fine for the boat, but you need to know the risks. If not for you, maybe for the next owner when you sell it.<br />PS Parrothead.. that is a nice old brochure.

 

[Spidybot]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

The insurance point is important. It rules out the conditions. If you wanna keep your lawful rights, you have to comply with the rules.

 

[dakotashooter2]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

There are some design factors to keep in mind also. Manufacturers don't just throw a hull together and say "here". Balance goes hand in hand with performance. While you "could" mount a 125 on such a boat you may be sacrificing not only performamce of the boat but of the motor. Motors are designed to account for a certain amount of "slip" when operating. Would you run your motor at full throttle while out of the water? No, because the RPM may get too high with no resistance. This can happen with an overpowered boat. You may notice wide beam boats generally have a higher HP rating. This is because the boat produces more drag and requires more motor but it is also able to distribute more motor weight, wha la, balance. Safe and efficient. As I understand most boats provide optimum balance/efficiency/performance at slightly under maximum HP rating. While you may seem to gain performance, which most people equate to speed, you are probably sacrificing motor performance by overpowering or underpowering.

 

[Spidybot]

Re: 1st post!: Chrysler Boat, 15' 6", what's the largest motor I can use?

Interesting point of view.<br /><br />At the end of the day we've argumented well for the rule of thumb: Stay within recommended specs - do not go lower than 75-80% of max hp if you wan't to enjoy the ride that your boat was designed for.