overpowering boats

[Bait O' Eggs]

Anybody put more horsepower on a boat than the boat is rated to?? How much safety factor do they have built in??

If a boat is rated at 110hp and you put in a 140 hp system would it be just a matter of time before you tore the transom off, or would a little reinforcing make up for the overpowering situation?

Considering taking out a 110hp mercruiser and putting in a newer 140hp mercruiser.

[SlabQuest]

The Coast Guard can confiscate your boat if it is powered beyond it's rating. At least that is what a dealer told me about OB boats. Also there are insurance issues.

[fish assassin]

I like Tim "The Tool Man" Taylors views on this subject ...
*NEVER* too much power!! UH, UH, UH, UH! :grin: :grin: :grin:

-assAssin-

[Thumper]

Well, I had a 200 on my 16 ft guide model Alumaweld flattie. Scary in a turn.

[Pilar]

Bait, you might try to find the rating nameplate for the boat. If it is old enough it prolly does not have one.

All new boats are required to have a visible, permanent plaque that lists load limits (passengers and weight), Horsepower limits and other info. I guess you could try to look up the boat and get the info off the web but I'm not sure how to do that.

Just because it came with a certain motor does not mean that it is rated for that size. Most Manufacturers underpower the boats they sell to cut costs.

On an older Fiberglass boat I would worry about the condition of the plywood bolster on the inside of the transom. On some boats the deck at the stern of the boat is water logged and rotted. If in doubt, chainsaw it out and replace it with new marine plywood. Dry rot of the wooden structural members will severely weaken a fiberglass hull if ignored. The consequences of this are obvious.

[ 06-03-2003, 01:51 PM: Message edited by: Pilar ]

[Bait O' Eggs]

The plate with the ratings states:

"This boat is built to accomodate under normal operating conditions an engine of not more than 110hp and 10 persons @ 150 lbs per person or a properly located max load of 2000lbs for person and gear"

Of course it would only take a few seconds to remove the plate

I only ask because of the newer 140 hp motors seem easier to acquire than the older 110 hp motors but I could be wrong.

Seems easy enough to me to build an aluminum fuel tank that would bolt to both the deck and transom on both sides of the motor. This would drastically stiffen the boat to help allow the transom to take the increased horsepower. [img]graemlins/1zhelp.gif[/img] But then again I have reloaded shells beyond the factory recommended allowable power loads, which resulted in taking the gun to the gunsmith to perform repairs after I fired the gun.

[id. painter]

My boat is rated for a 175hp. I put a 150 on it. At my alt. it is perfect. At sea level its almost dangerously powerful. Be safe. id. p.

[edsr]

BOE - Is there an issue of more power for your boat? Do you actually need additional power for the boat to perform? Under ideal conditions all boats can reach their maximum speed but when the conditions worsen speeds are reduced to displacement hull speed and a larger engine might burn a good deal more fuel for the same speed the smaller engine makes. This could make a real difference when reserves are limited.

Why not call a dealer of your brand of boat who sells boats and motors. Tell them you want to re-power to the max and I am sure they will come up with a number fast.

BTW - Your tuna plugs look awsome! I think that you are right the lead insert is a good way to go.

edsr

[Pilar]

Edsr, the issue is the 40 + year old boat. BOE owns or will soon own one of the first outdrives made by Mercruiser, a type IA or IB. It was a good unit and totally revolutionized boat powerplants but completely superseded and obseleted by the following generation. The transom cutout is exactly the same and so is the engine footprint in the boat.

Mercruiser did not make the newer type I outdrives in the 110 hp rating. They made a bunch in the 120hp or 153 cubic inch, 4 cylinder inline motor (same as the 1962 shoebox Nova) and the maxxed out 140hp or 181 (3 liter) cubic inch, 4 cylinder inline motor. The last 4 cylinder made by Mercruiser during this era was a total Mercuiser. The motor was aluminum and original design. I forget what they called this little beastie but it is a pain. High performance, high cost and somewhat rare now. All of the parts come from Mercruiser and they are expensive. They also made the inline 6 cylinder 250 CID Chevy motors into boat I/O units. A 165, I believe that was.

We get cores for rebuilds of this little 4 cylinder powerhouse (181 CID) from forklifts of all places and small commercial power generators. You can still find the 'Iron Duke' or 153 CI blocks but they are becoming rare.

The main differences in these two motors are the rocker arm ratios, cylinder head, cylinder bore and stroke, crankshaft, piston rods and carburetion. Other than that they are very similar with many interchangeable parts. And it is a Chevrolet car engine, what would you change?. You can find the parts in your back yard under the old tree.

You just can't get the old 110 hp motors anymore and I'm pretty sure you would not want them if you could get em.

The newest little Mercruisers are called 'Alpha' and they include the venerable 3 liter 4 bangers and 4.3 liter Chevy V-6 with the same basic outdrive.

Bait, can I see your boat sometime? I think the concerns you have are well founded. It all comes down to the transom. That and the fatigue the aluminum hull has experienced over 40 years. You are right on to worry about it.

If you went 140 you would have to revisit your load capacity for weight reasons. But you will do that anyway because if I were you I would add flotation foam, a huge underdeck fishbox and a huge gastank. All that would change your load restrictions for sure.

How many tuna does that bad boy hold .. that is what I am talking about.

:grin: :grin:

[Miss B Haven]

I would not sweat putting a larger hp 4 cylinder in this boat AT ALL. Same weight and no transom load to speak of. This is a lot different than hanging more hp and more weight on a transom. The stresses will be a lot less on that I/O.
If this startcraft is built like mine BOE- I replaced the wood in the transom without much pain at all. Double 3/4 marine ply - treated and epoxied together to make 1 1/2 thickness. It just bolts and rivets to the inside of the alum skin.

[Bait O' Eggs]

John
you do understand my questions well.

I called my uncle who was a boat mechanic for a local shop for 36 years before retiring a couple years ago. He sounds just like Pilar, Why do you want to buy an older boat and put a lot of money and work into it when the parts are hard to come by, and getting harder every year to get?

He didnt think the 140 would be any problem, my original thoughts have been to just replace the outdrive if this deal ever goes thru on this boat (same guy as the crab/shrimp pot deal, same estate sale). My uncle tells me, just because the outdrive looks like toast on the outside doesnt mean squat, just replace the housing for around $900 if the guts are all good. :whazzup: He also tells me the motors can be found, but are getting harder to get, I think John told me the same thing at least a couple times.

His recommendation is to spend my money in the fall on a newer glass boat ready to roll. I am having a hard time bringing myself to the glass boat conclusion, and I can picture this aluminum boat "customized" doing several things I want it to do.

I havent talked the guy into selling me the boat, and that is contingent upon a water test, so I guess I may be chasing my tail until he agrees to part with the boat. :depressed:

Must be time to call and bug him some more

[Pilar]

This fall when 'she' starts telling 'him' that 'she' does not want 'that' boat stored in the {Garage, yard, carport, whatever} .. your money will go about 2x farther than right now in the peak of the boating season. The price goes way down and people part with boats they do not want to store over the winter ... every year.

If you stay out of the TUNA! wars, Englunds and Costco you may even have a bigger pile of money to work with, to boot.

[Tilla]

Of course, according to one Northriver salesman they will put anything you want in their boats. [img]graemlins/eek13.gif[/img] Well I can tell you it won't be me!

[edsr]

BOE - I didn't realize that you were going to change from an I/O to a transom mounted outboard.
Pilar is right on all accounts.

Most likely if the boat was built to accomodate an I/O there might be insufficient transom support and bracing.

If you can get a new or refurbished engine it makes the most sense. I doubt there would be much harm in increasing the hp the amount you mentioned. Our market in OR is rather small but on the east coast and other places the search might be easier and quicker. I have a contact on the east coast who knows about older engines, let me know if you want his email.

Pilar is right-on about waiting until after the summer season is over for a good buy on a boat or motor, if you can wait.


edsr

[CAPT KUJO]

As a CG registered manufacturer of boats I can tell you that boats OVER 20' are not required to carry a horsepower or persons max ratings according to the CFRs. Mfg. of boats UNDER 20' are required to post both of those ratings and it is unlawful to remove that information.
That information is determned by a series of mandated CG test results and these test are required for all boat mfg whos vessel are less than 20 feet.

CAPT KUJO