raising 15hp outboard on transom using wood spacer (with pics)

[Sea Rider]

Re: raising 15hp outboard on transom using wood spacer (with pics)

If the engine is too poor for a given boat, whatever you do, raise engine, play with trim, adding fins, trim tabs, ballancing boat, etc won't make that boat plane. The issue is simple, too much hull drag to overcome with small engine. One thing is trying to plane, other while on plane. Try to get a good Samaritan to lend you a 25/30 HP short shaft engine, more power will guarantee having better hole shot to plane much faster. If that engine is rated for max 50 HP, what are you doing with a 15 ? Once you have installed a larger engine you can fine tune engine/boat configuration. All hull shapes are not same, some has less/more drag.

Owners manual AC Plate heights with respect of boat's bottom is only reference, if wanting boating perfection it's a trial end error issue to find that perfect height engine setting. Get a TT hour/tach, some generic tachs counts double rpm...


Happy Boating

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Most of the lakes I go to are pretty small, so I really don't need a 25-50hp motor. I can live with what I have and if there is nothing I can do to improve performance, I'll live with that for now. I was just hoping I could get more out of what I have.

So with that being said...if I am underpowered and the bow rises, do I have any options to improve performance with my current setup? Getting a different motor isn't an option at this point. I know I could redistribute the weight by moving the battery and gas tank forward, but sometimes my 3 yr old daughter and wife come along and I don't want to have my daughter to have access to mess with the battery or tank. I'd rather deal with the issues of having the weight in the back than move those items forward for now and in the end maybe I am stuck with my current situation. That's why I am looking to those of you with more experience to see if I have any options.

Would adding hydrofoil/fins be benefical in my case? At least to keep the bow down when I am alone? I have read that those help to keep the bow down which would be nice when I am in the boat alone.

I'll look into getting a tach too, since it would be good to know the rpms.

Thanks for all the replies!

 

[Sea Rider]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Keeping bow up means underpowered to break initial hull drag, nobody says to buy a 25/30, was just for testing issues. Meantime test without wooden shims, leave trim as posted pic place more weight towards bow, probably won't plane either but will slide much better as will have more hull on water. Don't run at wot all the time with that small engine, throttle down to 3/4, your engine will thank you...

Happy Boating

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Keeping bow up means underpowered to break initial hull drag, nobody says to buy a 25/30, was just for testing issues. Meantime test without wooden shims, leave trim as posted pic place more weight towards bow, probably won't plane either but will slide much better as will have more hull on water. Don't run at wot all the time with that small engine, throttle down to 3/4, your engine will thank you...

Happy Boating

If I have to keep the motor I have for now, I'd rather not know what I am missing with a bigger motor.

It just seemed like you were telling me to get a bigger motor:

...more power will guarantee having better hole shot to plane much faster. If that engine is rated for max 50 HP, what are you doing with a 15 ? Once you have installed a larger engine you can fine tune engine/boat configuration...

 

[Chinewalker]

Re: raising 15hp outboard on transom using wood spacer (with pics)

I really don't think you need more motor. You NEED to get the motor you have running better. Messing around with the trim, height, etc. is an absolute waste of time until you can verify that it is running on both cylinders.

Once you have verified that it is actually running as it should, THEN you can mess with props. The 9.5 x 10 prop should work fine with a light load, but if you regularly cruise with extra gear and passengers, then the next lower pitch prop might work better. Incidentally, your prop looks like it could use a trip to the repair shop as the blades appear to have been shaved back a bit.

A 14-foot tinny with a 15 is a near perfect set-up. I've run a similar combo for many years (25+). A good 15 will plane that boat of EASILY and will skip along at a good clip, even with some gear and a passenger or two. My 14-footer is rated for 35 and I've run everything up to and including 35 ponies, but I always go back to the 15.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

I really don't think you need more motor. You NEED to get the motor you have running better. Messing around with the trim, height, etc. is an absolute waste of time until you can verify that it is running on both cylinders.

Thanks Chinewalker. I'll do some research on learning how to test that it is running on both cylinders.

 

[Chinewalker]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Couple ways you can go about it. Easiest is probably to start the motor and note how it sounds. Stop motor. Pull one plug wire and ground it to the block (I've got a 12-inch wire with aligator clips at either end that I use, but a loose bolt or nail in the boot and touching the block should work). Start motor. If it sounds the same with no change in tone or performance, then it wasn't running on the cylinder you pulled. If it fails to start at all, then it was not running on the one you left intact. If it sounds like it has less power, then you may have been running on both all along. Try test with the other plug wire to verify, if that's the case.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Couple ways you can go about it. Easiest is probably to start the motor and note how it sounds. Stop motor. Pull one plug wire and ground it to the block (I've got a 12-inch wire with aligator clips at either end that I use, but a loose bolt or nail in the boot and touching the block should work). Start motor. If it sounds the same with no change in tone or performance, then it wasn't running on the cylinder you pulled. If it fails to start at all, then it was not running on the one you left intact. If it sounds like it has less power, then you may have been running on both all along. Try test with the other plug wire to verify, if that's the case.

Thanks! That sounds like something I can do. So basically this is determining if one cylinder is not getting spark. I pull one plug wire (leaving the plug in), ground it and try to start motor. Repeat for the other plug. If it doesn't start on one, then I know I am not getting spark in that cylinder, if it starts on one and sounds like the same power, there's a good chance the 2nd plug I test won't start. If it starts on each one alone and sounds like less power, then I can assume both cylinders are running.

Does this test replace using something like an inline spark tester to determine if there is spark? As long as I ground the pulled plug wire I am ok with starting it with one plug wire attached?

 

[Chinewalker]

Re: raising 15hp outboard on transom using wood spacer (with pics)

This test doesn't test for spark, specifically, rather it checks to make sure the motor is running on that cylinder. Causes could be spark, but could also be a bad reed valve, blown head gasket (not in your case, though, as compression is good and even), bad crankcase seal, hole in the fuel pump diaphram, etc. Any one of those could cause the motor to run on one cylinder.

Do the test and let us know what you find. If you find it's only running on one, then we'll help you narrow it down. If it tests okay on both, then you can move on to other things.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

This test doesn't test for spark, specifically, rather it checks to make sure the motor is running on that cylinder. Causes could be spark, but could also be a bad reed valve, blown head gasket (not in your case, though, as compression is good and even), bad crankcase seal, hole in the fuel pump diaphram, etc. Any one of those could cause the motor to run on one cylinder.

Do the test and let us know what you find. If you find it's only running on one, then we'll help you narrow it down. If it tests okay on both, then you can move on to other things.

Perfect, thanks for your help! I'll try to run it tonight and let you know what I find out.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Do the test and let us know what you find. If you find it's only running on one, then we'll help you narrow it down. If it tests okay on both, then you can move on to other things.

Good news, I was able to start it on each cyclinder. Using muffs, I ran it on idle for about 5 minutes with both plug wires attached. Stopped the motor, removed upper plug wire and ground it. Motor started right up and I could tell it was not as strong as with both plugs. Then I did the same thing with the lower plug wire and got the same result. So, it appears that both cylinders are working.

I am not sure what next steps to take besides the following:

I also took off the current prop and replaced it with the one I had on my '81 9.9 which is the same prop. So my next step will be to lake test the new prop and see if the old one was spun. The one I put on was in better shape than the one that may be spun, so I am ok switching them regardless if this doesn't solve anything. Hopefully in the next couple days I can get on a lake and test it out. I will post results after a lake test.

If you have any other thoughts in the meantime, I am open ears.

Thanks!

 

[Sea Rider]

Re: raising 15hp outboard on transom using wood spacer (with pics)

The upper pic, shows a visible 1/3 keel, assume the rest is near or flat keel to transom, if so, more hull drag to break inertia that a deep V keel which requires lew HP engines compared to flat bottom one. So your engine is working ok, hope prop is not spun. By the way, is it a tiller engine or a remote with center console ?

Happy Boating

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

The upper pic, shows a visible 1/3 keel, assume the rest is near or flat keel to transom, if so, more hull drag to break inertia that a deep V keel which requires lew HP engines compared to flat bottom one. So your engine is working ok, hope prop is not spun. By the way, is it a tiller engine or a remote with center console ?

Happy Boating

Yeah, the back half or so of the boat has a flat keel. It is a tiller, so most of the weight is in the back which I know doesn't help either.

 

[kfa4303]

Re: raising 15hp outboard on transom using wood spacer (with pics)

HI kg. Here's an interesting DIY "transom riser" that should give you more room to clap your motor to along with a DIY PVC tiller extender I made using 1 1/4" thin-walled PVC with a few slits in one end and pipe clamped to the tiller. It works like a charm cost about $3 and allows me to not only stand up while under way, which greatly increases my visibility, but I'm also able to shift my weight forward. Between raising my motor and adding the grab bar and extender my handling and ability to get on plane have increased tremendously.



http://www.youtube.com/watch?v=cZMR97duw_Q (more guys using tiller extenders)
http://www.youtube.com/watch?v=sTR4m5z46U0&feature=related
http://www.youtube.com/watch?v=5zC7cEuByNs

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

HI kg. Here's an interesting DIY "transom riser" that should give you more room to clap your motor to along with a DIY PVC tiller extender I made using 1 1/4" thin-walled PVC with a few slits in one end and pipe clamped to the tiller. It works like a charm cost about $3 and allows me to not only stand up while under way, which greatly increases my visibility, but I'm also able to shift my weight forward. Between raising my motor and adding the grab bar and extender my handling and ability to get on plane have increased tremendously.

View attachment 153887View attachment 153888View attachment 153889View attachment 153890View attachment 153891

http://www.youtube.com/watch?v=cZMR97duw_Q (more guys using tiller extenders)
http://www.youtube.com/watch?v=sTR4m5z46U0&feature=related
http://www.youtube.com/watch?v=5zC7cEuByNs

Thanks for the info, both of those things are something I can consider.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Ok, so I went on the lake this afternoon with the new prop. Basically had the same results. Bow up high, speed about 6mph. So the prop is probably not spun, unless by some rare chance they both are.

What I did try doing though was to let go of the motor and go sit on the middle bench seat. Very quickly the bow went down and slowly I got it up to about 12mph a couple of times before the motor would turn and I had to go grab the tiller handle. So with me moving up and re-distributing some weight, I got it to go on plane and increase the speed. I don't know if I would have had even more speed increase if I able to keep it straight for longer. Would my speed probably have increased the longer I was on plane?

To my inexperienced ears, the motors seems to rev up to where it should, it just doesn't get me on plane with all the weight in back.

So, assuming the motor is running fine (at some point I probably need to get a tach and make sure the rpm's are where they should be), it seems like I might need to just re-distribute weight forward. (unless raising the motor the couple of inches would make a difference in getting on plane?) However, like I said earlier, my 3yr old sometimes comes with and I don't her to be able to mess with the battery or the gas tank so I need to keep this in mind. I either need to build a box she can't access or teach her right away not to touch anything or figure out a way to get on plane as is.

The hydrofoils claim they can get boats on plane quicker for heavy stern boats, is it worth a try so that maybe I don't need to move things around? If I can get it to go on plane with just me in the rear and 12mph or so, I would be happy.

Thanks again for everyone's input! Everyone was new at this at one point right?

 

[kfa4303]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Oh yeah, we were (are) all new at this at one point. It seems you've learned one of your first valuable lessons which is that weight distribution is every bit as important as the weight itself, if not more so. The trick now will be keeping the weight where you want it to get the most out of your set up. I think you would benefit from either using a tiller extender, as I mentioned in my previous post, or a helm which you can place in the bow ("stick steering" set up), center (center console)(my current set up and very popular for fishing, or cruising) or side (side console) of the boat (classic bass boat/ski boat set up). I'm partial to the tiller extender myself because it's so simple and straight forward and lets me control both the throttle and steer simultaneously. Granted, I rarely use REV, so I don't really need shift controls much once I leave the dock, but as you can see from my previous links and doing some searching online, tiller extenders are becoming more and more popular. They even make them out of all sorts of exotic materials like carbon fiber with trim/tilt switches in them and the whole nine, but PVC is more in my price range and it works great I think you'll find the same is true with jack plates. There are some very nice, high dollar versions on the market, but you can often find DIY versions of the same thing that will work just as well for a fraction of the cost. Do a search here in the forums for more jackplate/transom raiser ideas. You'll get lots of opinions on "whale tales". Some folks swear by them, others not so much. I think you'll find that most folks don't use/need them once they have their rig set up properly. Overall, there are a million different interior combos and layouts you can go with. Post a few pics of your current set up and we may be able to make some suggestions.

 

[Sea Rider]

Re: raising 15hp outboard on transom using wood spacer (with pics)

What you need to do is seat a adult passenger 3/4 towards bow, place trim rod so to have a perpendicular engine with respect to sea level, place passenger at bow, full throttle, if planes, become a spotter, check water flow if passing above or below small upper plate, or slight above AC plate at wot to determine if in need to fine tune your height engine set up. If you don't have this very clear you could waste your time all day under trial and error. One thing is using a 15 HP engine for a boat rated for 35 compared to a 15 on a half bottomed hull rated for 50. Yor are comparing a 250 cc against a 700 CC if both were 2 strokes. That's why is good to test that boat with at least a 25 HP...

Happy Boating

 

[pootnic]

Re: raising 15hp outboard on transom using wood spacer (with pics)

So you didn't raise the motor for the lastest sea trial?
Ever little bit is going to help you.If you do try a hydrofoil it has to ride on top of the water to be any good,if your motor stays deep it is only going to cause more drag.
A smaller pitch prop MAY help you as well but without a tach rpms could be out of whack once on plane...

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Thanks again for everyone's input.

OK, I took the advice about re-distributing some weight. Over the weekend I moved the battery to just behind the first bench seat. I also used just part of the wood spacer to raise the motor up a little (the cavitation plate is about .25" below the boat now). I took it out yesterday and things worked out much better. It planed pretty easily, the bow didn't get very high and I got it up to 14mph with me just sitting in the back. I went fishing to a pretty small lake, so I didn't run WOT for super long time, maybe I could have picked up more speed if had more room to run it for longer.

I also ordered a tiny tach so that I can figure out rpms to make sure I am in the right range at WOT. Once that comes I'll test it out and see how the rpms look. If they are in the right range, I can live with the results I got yesterday. If they are off, then I can look to see what I can do to get the motor running right.