posted 05-30-2004 09:06 AM ET (US)
[This article has been moved to this forum from THE GAM forum. The PERFORMANCE FORUM is the preferred location for all articles discussing re-powering.]The transom height relationship to engine shaft length is somewhat similar to the classic relationship between a cart and a horse. You can't put the cart before the horse.
When the transom for the 1976 Outrage 19 was designed, it was made to fit the motors that existed at that time, and those motors evidently were 20-inch shaft motors. Overtime, as motors began to be made in longer shafts, transom heights were increased to match. Now it is possible to get motors with 30-inch shafts, and as a result we see that some of these old classic hulls are not being molded with a transom height appropriate for a 30-inch motor. The GUARDIAN 22 is made this way. If mounting a single engine, you order the hull with a taller transom and use a 30-inch shaft motor.
I do not recall any articles in the CETACEA collection that show a 20-inch height transom being raised to 25-inch height. Please mention which article you were referring to. There is one article that shows raising a 15-inch high transom to 20-inches on a 13-foot hull, and another article showing conversion of a notched transom to a full transom/bracket installation, but I do not recall any articles showing raising of a 20-inch transom on a larger boat to a 25-inch transom.
You mention "scuppers", but I don't think the OUTRAGE 19 has scuppers. I believe it just has the typical transom splash well drains. If you expect the transom to be continually filled with water by back flow through the drains, you could simply plug the drains with rubber stoppers. Install a 1000-1500 GPH pump to evacuate any water that does come aboard into the splash well. You can control the pump with a float switch. If you get into a pickle and need to really drain the splash well, you can open the drains, too. This is quite a workable solution. LHG has been operating his OUTRAGE 18 like this for years. I also have my REVENGE 20 set up like this. By the way, the splash well pump does not even run that often. In two weeks of cruising the coast of British Columbia, I think the pump only ran twice, and that was in some odd wave pattern situation in a rapids. Now if you plan to make a habit of backing into 4-foot waves, yes, the pump is going to run more often.
In general, I would not encourage you to undertake a significant modification to the transom unless you were very confident in the ability of the modification to be done to a very high level of craftsmanship. The fact that you are asking for advice on how to make the modification is, to me, an indicator that perhaps you do not have confidence in the craftsman available, be it either you or the dealer.