Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

[seedlings]

1979 AMF Crestliner Muskie 550 14'
1978 Evinrude 70hp
13.25 x 17 pitch prop
30mph, 4500rpm WOT with normal load of 2 adults, 2 kids.

Just getting this boat going after a couple of decades in storage, and now am trying to improve performance. After reading here about adjusting Manual trim by how the AV plate looks in comparison to the bottom of the boat, here's how it looks now. I raised the motor about an inch and a quarter (two holes), and the trim out two holes. We had trouble getting on plane, it takes about 45 seconds, plus couldn't get over 15mph (trying to get a tube out of the water).

This has raised the top of the motor mount above the boat. Is this OK?

And finally, the back fin of the lower unit had been bent, chipped and broken. I tried to tap what was left back in place, but lost another 1/4 inch of metal under the prop. Tell me how bad is this?

Thanks all,
CHAD

 

[fabrimacator21]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

Well... it's a no brainer that you need to go back down on the trim... 45 seconds is WAY to long to hit plane. Just looking at your pics, that looks like a REALLY extreme angle for trim.

As far as the plate on the fin goes it really isn't hurting anything(the chip that is. It does need to be straightened if bent)... If you have access to a tig welder you could patch it back together but if you don't, then either leave it or take a cut off wheel to it, and make it a straight line. Can always come back later and weld a piece to it in order to get it back to stock (although I don't think it's necessary)

Those fins are real tricky to straighten. Real easy to bend em too far or too many times and they like to break because of them being poor quality cast aluminum.

Best method I've found is a big rubber mallot or deadblow(5 bucks at harbor freight) and go real easy on it. You want to bend it as few times as you can. The more you mess with it, the more likely it is to break.
If you use an actual hammer it WILL break.


I really don't know on the motor height though... no experience with outboards.

 

[tashasdaddy]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

you are trimmed way out. drop one hole at a time, until you get to a happy medium. good hole shot, and good plane attitude. the closer the lower unit is the the transom you push the bow down, the farther away, you push the bow up. that prop needs to be dressed.

 

[fabrimacator21]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

Not trying to nit pick here but those studs on your trailer are rediculously long... 4-5 inches too long... just gonna end up as needless grinding at steep entrances.

 

[abj87]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

are thoese your tiedowns?

 

[Tacklewasher]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

Few things.

4500 rpm WOT is too low. I think a 17p prop is too much for a 70 hp. I run a 115hp on an 18ft and run a 15p. Ideally you want your rpm to be 5500-5800.

But deal with set up first.

I think you still need to raise your motor. Go to the last hole. and if it ventilates, than put it back down, but I don't think you will vent. Having the bracket higher than the transom is a non-issue as it provides no support. All the weight is held by the 4 bolts.

Then tuck the motor in one more hole as TD suggested.

Use a grinder to get the lumps off your skeg and straighten it. If you want, you can add a skeg guard but I don't think yours is that bad yet. While you have the grinder out, trim those bolts. File the prop down and see what that does for you.

 

[tashasdaddy]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

that motor without trim. will give the best overall performance at 90* to the bottom of the hull. your AV Plate should be on the same plane, (inline) with the bottom of the hull. i would try this before doing anymore height adjustment.

 

[countvlad]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

Few things.

4500 rpm WOT is too low. I think a 17p prop is too much for a 70 hp. I run a 115hp on an 18ft and run a 15p. Ideally you want your rpm to be 5500-5800.

But deal with set up first.

I think you still need to raise your motor. Go to the last hole. and if it ventilates, than put it back down, but I don't think you will vent. Having the bracket higher than the transom is a non-issue as it provides no support. All the weight is held by the 4 bolts.

Then tuck the motor in one more hole as TD suggested.

Use a grinder to get the lumps off your skeg and straighten it. If you want, you can add a skeg guard but I don't think yours is that bad yet. While you have the grinder out, trim those bolts. File the prop down and see what that does for you.

i agree ... the WOT is low.... and i believe thats your planing problem... i have a 120 with a 15 SS on a 19 renken CC deep v and im running 5800 WOT

try a 13 and go from there.....

 

[seedlings]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

To clarify, let me say that all the problems I had were before the motor was set like this. I haven't taken it out after adjusting to this setup. If you can imagine, the motor was an inch and a quarter lower, plus trimmed all the way in to the rusted hole.

Thanks for the tips, all. Let me see if I can get them down here:

^ Trim one hole toward the front of the boat (fabrimacator21, Tacklewasher, tashasdaddy)
^ Raise the motor another hole higher, to the top hole (Tacklewasher)
^ Lower the motor one hole (tashasdaddy)
^ Trim the studs

+ Try a 15 prop, or maybe a 13

I've already filed down the prop, but there are still indentations in a couple of the blades.


Yes, abj87, those are my vintage tiedowns (the chain and spring clamp).

CHAD

 

[seedlings]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

Also, do marinas generally let you "try out" a prop before buying it?

CHAD

 

[fabrimacator21]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

Also, do marinas generally let you "try out" a prop before buying it?

CHAD

Prop shops/boat dealerships will usually let you demo a prop... I believe you give them a deposit and if you damage it then you just bought it.


Your problem does sound like too much prop though. I didn't realize it was doing this before you moved the trim. With that being said the more you go up on trim, the harder it gets to get on plane. I'd try the hole after the bottom hole and see how it acts with a 13p prop.

 

[Tacklewasher]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

^ Trim one hole toward the front of the boat (fabrimacator21, Tacklewasher, tashasdaddy)
^ Raise the motor another hole higher, to the top hole (Tacklewasher)
^ Lower the motor one hole (tashasdaddy)

Don't think that's what he meant. I think TD just meant to trim in the one hole and do that before messing with the height (which I do agree with).

+ Try a 15 prop, or maybe a 13

Play with the trim first, then try adjusting the height. Once you get your current set up straightened out, the post results before spending money on a prop. Do all the free things first.

 

[seedlings]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

If rain holds off the boat will be in the water tonight for a test, but I won't have my usual load of wife and kids. I'll have one adult friend making about 200lbs lighter than usual.

I really appreciate the advice and insight from all members. Please don't get weary from us cliche` new-boaters with the same-ol questions month after month. You do a good thing.

CHAD

 

[seedlings]

Success!

Success!

Good news, and I'm excited!

Went out tonight with the trim in the 2nd hole as recommended, and made it to 36mph (up from 27mph) at just over 5000rpm (up from 4500)! Granted, I was absent about 150lbs of typical passenger load. (also tried at the third trim hole, which didn't seem to help/hurt anything) My passenger went forward and aft without much change in performance. The bow doesn't ride as high and I can "see" better over the top without kneeling in the seat. All around better performance!

The AV plate stayed a couple of inches below the surface of the water at full plane. Does this sound good?

I'm going to keep this prop.

Thanks again for the kind help!

CHAD

 

[fabrimacator21]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

So your motor was just too low?

 

[kbomb]

Re: Success!

Re: Success!

Good news, and I'm excited!

Went out tonight with the trim in the 2nd hole as recommended, and made it to 36mph (up from 27mph) at just over 5000rpm (up from 4500)! Granted, I was absent about 150lbs of typical passenger load. (also tried at the third trim hole, which didn't seem to help/hurt anything) My passenger went forward and aft without much change in performance. The bow doesn't ride as high and I can "see" better over the top without kneeling in the seat. All around better performance!

The AV plate stayed a couple of inches below the surface of the water at full plane. Does this sound good?

I'm going to keep this prop.

Thanks again for the kind help!

CHAD

That's awesome. I'm glad it's way faster! Do you have a pic of your whole boat to post here? I think it might look like mine...

 

[seedlings]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

So your motor was just too low?

I guess... Raised the motor, trimmed it out 15 degrees or so, and gained 8mph and 600-700rpm. I hit 30mph and 4500rpm once before adjusting, but 27-28mph and 4400rpm was typical.

It felt faster too. Maybe now we can pull a tube at 25mph instead of 15mph.

CHAD

 

[Mark42]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

The prop does need a little attention until you get a replacement. Try your best to straighten any wavy edges. A hammer and wood block work well. Also follow what other members posted about straightening.

When the leading edges of the blades are back as close as possible to original shape, then sand any rough edges smooth. Rough edges cause cavitation and loss of power.

If there are small nicks and chips, use thickened epoxy to build up the missing pieces then sand smooth. Have done this with a few aluminum props on a 40hp outboard and the epoxy holds up fine and the prop runs smooth with less vibration than a chipped up prop.

This simple maint might get you through the rest of the season before needing a new prop.

Another modification that REALLY helps get a small boat up on plane is the prop ventilation holes. OMC issued a tech bulletin on how to do this. It boosts hole shot with no loss of top end power.

 

[seedlings]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

The prop does need a little attention until you get a replacement. Try your best to straighten any wavy edges. A hammer and wood block work well. Also follow what other members posted about straightening.

When the leading edges of the blades are back as close as possible to original shape, then sand any rough edges smooth. Rough edges cause cavitation and loss of power.

If there are small nicks and chips, use thickened epoxy to build up the missing pieces then sand smooth. Have done this with a few aluminum props on a 40hp outboard and the epoxy holds up fine and the prop runs smooth with less vibration than a chipped up prop.

This simple maint might get you through the rest of the season before needing a new prop.

Another modification that REALLY helps get a small boat up on plane is the prop ventilation holes. OMC issued a tech bulletin on how to do this. It boosts hole shot with no loss of top end power.

^^ I will do that vent hole mod! I'll also try the epoxy. What brand/type do you know that works well?

That's awesome. I'm glad it's way faster! Do you have a pic of your whole boat to post here? I think it might look like mine...

Similar, but mine's a Tri-Hull with open bow. Here you go:

CHAD

 

[Mark42]

Re: Did I do it Right? Adjusting Manual Trim, AV Level (Pics)

Regarding the epoxy, if you have some left from boat building, it would be the best as it is the purest form of epoxy you can buy (most have no fillers so its stronger than the hardware store stuff).

I have also used the epoxy that comes in the double plunger tube applicator (most "blister pack" epoxies have fillers). If you can find a pack labeled "Marine" it would be worth the extra dollar or so. I see it in Lowes and Depot for about $6-8 or so.

Either way, the epoxy needs to be thickened so it will stay where you put it. For this sort of temporary fix, just use plain old wheat flour (from your pantry). Mix the two part epoxy as per instructions. THEN add the wheat flour to thicken. When it gets like peanut butter consistency, apply it to the prop. Be sure the prop was sanded to bare aluminum and wiped with alcohol or acetone to ensure a good bond. Apply a little more than you need, then sand to shape and shoot a little spray paint to seal it.

I find that if the best blade is traced onto paper, then cut out, it makes a good "gauge" to hold up to damaged blades to identify the bad spots, or to make them all even.

I have come to the conclusion that a patched up prop is much better than running a "rough" prop. Its smoother, and the reduced vibrations will keep the prop shaft seals from premature wear and leaks. And that's a good thing!

So even if this is not the best professional repair, it has its advantages over doing nothing.