CONTINUOUSWAVE

I have a 1979 Outrage 21, and I seek advice on engine size limits. I may put a 225-HP engine and a small auxiliary engine as back up [on the 1979 OUTRAGE 21 boat]. [Give me] any thoughts on this.

The [transom] is in perfect condition and had twin 90-HP engines previously.

As you can see in the Specification table from the Reference Section, http://continuouswave.com/whaler/reference/specifications.html, the Outrage 21, available from 1970-1982, had a maximum hp rating from the factory of 200 hp.

Given the desired increase to 225hp is only marginally more than the factory limit, it should not be a problem. This presumes the transom is in proper condition and has no damage.

Keep in mind total engine weights of the main and auxiliary engines. If you select 4 stroke motors, it is highly recommended you temporarily simulate the added weight in the stern and observe how it affects static trim and performance.

There is no limit on size of an engine, other than the practicalities of mounting it. Only engine horsepower is limited by the factory rating. Boats longer than 20-feet or made before 1972 were not bound by any federal regulations on horsepower, but it was common that a manufacturer would state the maximum horsepower, as Boston Whaler has and as Phil has noted in his earlier reply.

Limits on engine weight or transom were never routinely given until just recently. Even now, not every boat has a specified maximum transom weight limit.

A good indicator of how much weight should be on the transom can be taken from the position of the engine splashwell drains. The splashwell drains are in intended to permit water to drain out of the splash well, and the outlet of the drain at the transom should be above the static water line of the hull. If the splashwell drain outlet is below the water line, it should not be so far below the waterline that water flows into the splashwell. If the drain outlet is deeply submerged and fills the splashwell with water, then there was too much weight on the transom.

Note that if the transom is so deeply submerged that the splashwell drain is submerged and the waterline becomes higher than the splashwell height, then the drain begins to down flood the boat, which was clearly never the purpose of that through-hull fitting. A boat being down flooded at the stern by the splashwell drain is at risk of further immersion as the weight of water in the stern of the boat increases. The water coming aboard will lower the stern even further, and if the top of the transom notch reaches the waterline, then very rapid down flooding of the engine splash well will occur, usually leading to flooding of the cockpit. This is a closed-loop positive reinforcement system, and very careful consideration should be given to prevent this from ever occurring. Once any boat has a lot of free-to-move water aboard in the cockpit, the stability of the boat is severely compromised.

Diver1966 wrote:...I may put on 225-HP engine and a small auxiliary engine as back up [on the 1979 OUTRAGE 21 boat]. [Give me] any thoughts on this.

Unless your goal is to able to hit speeds greater than 55-MPH, I don't see a need for a 225-HP engine on a c.1979 21 OUTRAGE. Boston Whaler founder Dick Fisher only had a 85-HP engine on his personal 21 OUTRAGE. See

http://continuouswave.com/whaler/refere ... ABoat.html

Phil T wrote:...the Outrage 21, available from 1970-1982, had a maximum hp rating from the factory of 200 hp.

That rating was most likely for the engine power at the crankshaft output, not at the propeller. You would typically de-rate that by 10-percent to get the shaft horsepower rating, 180-HP, as would be used today to measure the power of a modern outboard engine. Outboard engines did not change to rating power at the propeller shaft until the ICOMIA 28-83 standard came into use, which would have been after c.1983. For more on ICOMIA 28-83 see

ICOMIA 28-83
http://continuouswave.com/whaler/reference/ICOMIA28-83.html

If a modern 225-HP engine is used, then boat is over the maximum power rating by 45-HP. As a percentage of 180-HP, 45-HP represents a 25-percent increase over the maximum rating. This is much more increase than would be attributed to an increase to 225-HP from 200-HP, which is only a 12.5-percent increase.

While Phil described the 225-HP engine as being "only marginally more than the factory limit", I think that is misleading. The 225-HP engine would be 125-percent of the original factory rating. Is 125-percent only "marginally more"?

Also, in the past many engines did not actually produce their rated power output, but since the imposition of exhaust gas emission limits on certain exhaust gases which are limited in the amount produced in units of grams/kW-hour, accurate establishment of engine power output is necessary to know the true rate of exhaust gas emission. This has led to the engine power being very firmly and accurately established.

A modern 225-HP engine is quite likely to weigh more than a c.1970 200-HP engine and probably more than the twin 90-HP engines that were once on this boat. When the weight is augmented with a second modern engine as an auxiliary engine on the transom, there is no doubt the transom weight will be greater than any weight experienced when the boat was newly designed, 49-years ago.

Thanks for the info and advice.

I had a 200 Opti on my 1978 Revenge. That was SCARY! Now I have a 115 4 stroke and feel that to be a perfect combo.

Thanks GRH.

I've gone with one Yamaha 90