Raising the engine

[Glenmac]

What exactly does raising your outboard engine accomplish other than possibly increasing your rpm's and when do you stop in height. I raised mine to place the cavitation plate about a half inch above the bottom of the boat because my rpms were a little low. It didn't do much (maybe 100 rpm increase) and am about to change from a 19 pitch to a 17 pitch prop. Still learning and trying to get the optimal set up for my boat and motor. (Rec range is 5000-6000 for Yamaha 115 preferably around 5500 to 5700). I can only reach about 5200-5300rpms). Also porpoises between 3000-4000 rpm then planes nicely when I push thru. Dealer talked about putting "wedges" on the transom to see if that might help. Trims nicely at WOT with no porpoising.<br /><br />Any advice would be appreciated.<br />Having fun learning,<br />Glen

 

[PAkev]

Re: Raising the engine

Glenmac,<br /><br />Raising the outboard is commonly termed "trimming" the motor and enables the boat to plane on water most efficiently.<br /><br />Most newer Yamahas have negative trim which enables you to slightly tuck the motor under the transom to get a little more lift than other conventional OB's. During the initial power up complete down trim enables the transom to lift up which pushes the bow down. This enables you to get onto plane the quickest and enables you to have a clearer view of the water ahead of you. However, when the trim is left in this position while on plane, your bow is incurring the most friction as it displaces more water. Therefore, "trimming up" enables you to get a few more MPH or enables you to cut back on the RPM's in order to maintain the same MPH as the bow displaces less water. "Trimming up" also reduces less lower unit drag in the water and improves handling performance and economy. <br /><br />Powering onto plane when the motor is "trimmed up" will indeed create the porposing effect which you described as it pushes the transom down which forces the bow up. This practice will also diminish control as your steering is compromised with the bow out of the water. Eventually the bow will come down as the boat planes out but will take much longer than when using your motors trim features.<br /><br />Kevin

 

[Glenmac]

Re: Raising the engine

PAkev,<br /><br />Thanks for the answer. Are you talking about "trimming" meaning use the trim and tilt on the engine to obtain a more efficient plane? I was talking about actually raising the engine up in the transom one hole to bring the entire engine higher. (Or is that what you were talking about?) How high does one raise the engine before stopping or reaching max benefit?<br />Thanks,<br />Glen

 

[Solittle]

Re: Raising the engine

Kevin is writing about trim/tilt & gave a great explanation on how to use it to get best effect.<br /><br />Your base question deals with the position of the motor on the transom. Most of the "experts" here will recommend that you start with the cavitation plate about 1" above the bottom and go from there. It becomes a point of dialing it in to your particular motor/hull/load at that point. You can get into jack plates if you are looking for the max in performance. The beware of searching for the max hight for performance is not to go so high that you get above the water pick-up for the waterpump. You can monitor this point by having a water pressure guage. Some will even push that by plugging the top holes in the water pick-up grill or plugging them all and going for a high speed pick-up.

 

[Glenmac]

Re: Raising the engine

SoLittle,<br />Thank you. I am running a bassboat and not looking for tight control of speed etc but just trying to optimize settings for my boat which is a Crestliner, CMV, 1750 (modified V hull.) I just pulled my prop and am taking it to the dealer. One concern, when I pulled the cotter pin, the prop nut was loose and I could turn it by hand and didn't even need a prop wrench. Noticed the the hole for the cotter pin was almost all the way to the end of the nut. So will ask the dealer about that. I was just trying to find some tips on when to stop raising the engine. I might leave it where it is for now and see how the prop changes things.<br /><br />Thanks again....all advice appreciated.<br />Glen

 

[Solittle]

Re: Raising the engine

Glen - Your prop was installed correctly. No need for a prop wrench. I use an adjustable plyers if needed. On my johnny rudes first thing that goes on the prop shaft is what I think is called a thrust washer, then the prop, then a nylon spacer thing, then the prop nut & cotter pin. I put the prop nut on finger tight and then tighten it up just enough to get to the next slot of the prop net for the cotter pin.<br /><br />Make sure you take it all off once in a while and apply a liberal coat of marine grease. I spent about an hour last week as one of mine was stuck.

 

[Glenmac]

Re: Raising the engine

Thanks, your response is what the dealer said to do. The manal that comes with my engine states that it should be torqued to 40lbs. So I just put in back on and tightened it some then re-inserted a cotter pin. Oh...also lubed the prop shaft real well before starting all this. I am hoping that using this new pitch that I will increase my rpms (hopefully not loosing top end). Dealer says that I shouldn't lose top end with this small of a change but probably would if I dropped it any further.<br />Thanks again,<br />Glen