TOPIC: Maximum Horse Power?

Hello,
I'm looking for a mid fifties outboard for my 1954 Klamath Trailorboat. I think that my boat is a Klamath model, but I'm not positive. The brochure says the max HP is 16 HP. What determines the max HP? Is it the weight of the motor compared to the boat? I have a newer, 1975 Klamath with a 15 HP Evinrude, when I go out by myself, with me sitting in the back, it wants to ride with the bow VERY high, unless I go slow. I think this would not happen if I get a tiller extension and sit on the middle bench. Eventually, I hope to have a steering wheel on the console of the 54, so my weight will be more centered. I've been hoping to find a 15HP or 18 HP Evinrude Fastwin for the 54, but have not found one yet. There is a pretty nice 25 HP Johnson Seahorse for sale locally, would it be way too much motor for the boat?
Thanks,
Chris

I found this guid on tin boats
www.tinboats.net/forum/viewtopic.php?f=4&t=12144
I need to measure my transom, but it looks like if I get the steering hooked up, 25 HP will be ok.

IF it was MINE, I would stick to the recommended HP. - The USCG, game wardens and other authorities also agree to NOT overpower boats.

A 15HP OB by Gale, SeaKing, Johnson, Evinrude or Mercury should be FINE.

just my OPINION, satx

I didn't realize how narrow my boat gets in the back, when I first got it, I measured it at the oar locks to see if the oars that I have for my 75 Klamath would be right. Both boats are 5 ft at the oar locks. The 75 maintains the 5 ft. all the way to the transom while the 54 tapers to 4 ft. Taking that into consideration, I will pass on the 25 HP motor and continue looking for a mid 50s 15 HP motor.
Thanks,
Chris

Hi Chris. I live over the hill from you a bit past Reno. I have a very nice 1962 (Gale) Sea king 15 hp. I'm not sure at this point if I want to sell it as I planned on putting it on my 14'6" aluminum but, I do have 3 fastwins I could use also. I just sold a 15 hp 1956 Evinrude and may have another one for time to time. Fifties Evenirudes are my favorits.
I am looking for a 65 to 80 hp Mercury 4 cyclinder 2 stroke longshaft for my bigger boat. Hugh

The formula for O/B hp is centerline length times transom width - factor.

from that point it depends on whether your boat has a 20 inch transom or less than 20 (actually 19 inches or more is considered 20) and whether it has remote steering. remote steering is a wheel. or stick steering or anything other than steering with the tiller on the engine. Look here for an explanation of it all. http://newboatbuilders.com/pages/hp.html

Also if the boat tapers toward the transom (becomes narrower) you can use the widest point in the aft 1/4 of the boat. However as was said if the label say 16 go with that. State and local law enforcement get upset about values that exceed what's on the label. Most states now have laws prohibiting exceeding those values.

So then how do the heavy 4 strokes and also propshaft rated motors fit into this picture ??

I always wonder about the CG formula. My buddy has a 17' boat ( inboad jet ) that is shallow in the back and about 65" wide, yet it has 450 hp?? Differant formula for inboards? Just wondering.

The USCG hp regulation only applies to outboards under 20 feet in length, not inboards. The formula is different for different types of boats. Flat bottom hard chine boats with transoms under 20 inches and that have tiller steering have the lowest. Boats with 20 inch transoms and remote steering have the highest.

4 strokes and propshaft rated boats haven't really changed anything because the formula is very conservative. If the US used a maneuvering test or a collision avoidance test then the rating might (might) be higher. The USCG and ABYC did a series of tests using both the formulas and the tests and some boats, particularly tiller steered boats were overrated using the formulas and couldn't make it through the tests. But larger modified v and deep v boats were under powered using the formulas. But it all evens out because everyone has to use the same method.

As to law enforcement many states have passed laws making it a violation to exceed the values on the capacity label. So, yes you can be cited by state or local law enforcement. The USCG cannot cite you for overpowering because it is not a Federal regulation. The regulation to put a label on the boat applies to boat manufacturers. However if you are operating in a reckless or erratic manner because the boat is overpowered they can cite you for negligent or grossly negligent operation. Negligent operation can net you a fine. Grossly negligent will get you a vacation on the government ticket.

P.S. There is no USCG requirement for inboards

Hi Hugh,
I recently purchased a 1955 10 HP Johnson Seahorse and a 1957 18 HP Evinrude Fastwin. So I think that I have the motors that I want for now at least. I'm still looking for a 50s era steering wheel, pulleys and remote controls for the Fastwin.
Thanks,
Chris