115 wont go past 4800 rpms

[Merganser]

Took boat out in flat/mild chop conditions after outboard has been lowered to lowest setting.

WOT 4500-4700 rpms

Tilt up increase to 4800-5000 rpms at WOT

Manufacture recommends full HP at 5500 rpms and max 59-6300 rpms

This is with a 13.5-15 pitch prop

So lowering outboard appears to address ventilation, However There is no change in over all RPM and outboard still under preforming.

[pstephens46]

So I looked up this type of boat on google. Built of wood, epoxy and fiberglass.
Have you ever actually weighed it? Looks pretty stout...
Any barnacles or issues with bottom?
1100lbs seems light after looking at pictures. I fished on a boat last week in the Gulfstream. Built with similar components. 60 ft and 55,000 lbs. 8000lbs of engines but still very heavy due to the construction.

[zenoahphobic]

OP your last post you say trimming out the rpm's increased.
I would note that angle and determine if it was excessive by looking at the hull line sideways. I have a feeling it is and that suggests the engine is too low.
That boat appears to be very heavy and may have a lot of drag - check the smoothness of the hull also.
Any boat with a lot of weight can experience ventilation when powering off hard, in spite of the engine set at the correct height. You may need a high thrust prop (bigger blades/diameter or four blade), as you suggested going down a pitch did not change things (much).
I would still check the cable setup, you simply push your lever fully forward/ down and observe whether your throttle is fully opened (will need some dismantling though, and/ or expert not to void warranty).
If the above confirm to be true, you have a task to get this setup to work better. More knowledgable experts need to have a very good look at it, one of whom should be a propeller guru.

[Merganser]

The dolphin plate, or cavitation plate is at level with bottom of transom. Similar boat with 90 Hp get up to 26 mph about, Boats are heavy looking but plywood epoxy lighter than aluminum boats comparing weight per sq ft. There is active forum of builders of this boat, and I have not seen this issue come up there before and several builders with next size up from mine 24' with 8' beam and full cabins and 80 gal fuel are able to run 115. These are very efficient hulls. This hull is very smooth and there is no growth or anything like that in play.

I will also follow up with paperwork when I contact dealer about hydraulic steering, still leaking (another issue).

Will talk to dealer about prop/cable issue.

And paperwork!!!!

Thanks for the advise,

[zenoahphobic]

The dolphin plate, or cavitation plate is at level with bottom of transom. Similar boat with 90 Hp get up to 26 mph about, Boats are heavy looking but plywood epoxy lighter than aluminum boats comparing weight per sq ft. There is active forum of builders of this boat, and I have not seen this issue come up there before and several builders with next size up from mine 24' with 8' beam and full cabins and 80 gal fuel are able to run 115. These are very efficient hulls. This hull is very smooth and there is no growth or anything like that in play.

I will also follow up with paperwork when I contact dealer about hydraulic steering, still leaking (another issue).

Will talk to dealer about prop/cable issue.

And paperwork!!!!

Thanks for the advise,

Accepting that the boat is not overly heavy and a "very efficient hull" and backed by other examples, maybe the plate level with the bottom indicates, with a 6 inch offset from the transom, that the engine(lowered) is mounted far far too deep such that you will never get the engine to fully rev out.
Such an offset typically requires the engine to be raised by 1 or 2 inches from that it would be if mounted straight on the transom.
Your trim angle also comes into play by how far the engine prop is actually away. For example a transom that has a steep leaning angle, the engine would be trimmed away from the transom further than a vertical transomed boat with the engine running vertical.
I am suggesting sometimes these transom brackets can cause problems; your engine may well be running in an area of turbulence, in an area of raised water and not in "clean" water (maybe acting in contradiction of the intent of addition of the bracket).
I would sort the height out first then the issue of the "ventilation". Chicken and egg thing.
That boat forum sounds like a good place to sort this out with fellow like boat owners. If these are homebuilt, I would have have to be thoroughly convinced that this problem has nothing to do with it's build.

[Merganser]

Thanks for all of the comments and suggestions. After all of the possible scenarios in the end I found the problem to be the most obvious, though the last one I would have expected having had the motor professionally installed.

I was going to see if perhaps my throttle linkage cable was not adjusted correctly when I took cover off I noticed the spark plug cover for the No. 1 plug was laying on the bottom of the engine cover. Meaning from the time I picked out boat from dealer after outboard was installed I have only been running on 75% power from 3 cylinders. After small throttle cable adjustment and taking plug out to make sure it was clean and reinstalling it WITH COVER ON I took boat back out.

With all my commercial fishing gear, spare anchor and chain, survival gear, tools and 6 gallons of water I was on step at 36-3800 rpm with outboard all the way down, trimming brought me up to 42-4400 rpm.

Increased throttle easily to 5500 rpm and easily able to reach 5700 rpm.

Hull speed of 30 mph (GPS) this is equal too what another widebody builder achieved with a 140 Suzuki on same hull but larger cabin.

Based on comments I was speculating I possibly did have exceptionally heavy boat.

I reviewed the Tolmam builders forum and found that most boats in 22-24 foot range with cabins or center consul steering stations were between 2200-2500 lbs with gear, gas ect... I put mine at heavier end of range since I carry commercial fishing gear, totes, a pretty well loaded survival bag (since I fish in S.E. Alaska) and survival suit, plus the weight of my 9.9 which I use while *****ing.

However once I addressed plug (which dealer didn't notice) my boat preformed exactly where I wanted it to be.

Just an FYI since folks were commenting on weight

Plywood weighs about 35 lbs per cubic foot. Add for epoxy and fiberglass 15-20 lbs

Aluminum weighs 168 lbs per cubic foot

fiberglass (Whaler or C-dory....) weights about 95 lbs per cubic foot


So even, if I had made my boat EXTREMELY heavy say 70 lbs per cubic foot-doubling the weight of plywood per cubic foot I would still weigh less than comprable Whaler, C-Dory or Alumaweld for same size by 25-98 lbs per cubic foot respectively.

So with 115 and 15 pitch prop I found I preformed right as expected in terms of hull speed and acceleration based on how I loaded boat and there was not a hull or build issue, once I was using all 4 cylinders.

Rather my issue was I should have not assumed everything was as it should have been when I picked up from dealer, and I should have checked plugs and throttle cable myself.

Lesson learned.

Thanks again for feed back.

Josh.

[panasonic]

Glad you got your problem fixed..hard to believe that you got that from the dealer like that.....Do the proper maintenance on it and it will be a good engine for you.

[99yam40]

good to hear it is running well now.
what do you mean by
"the spark plug cover for the No. 1 plug was laying on the bottom of the engine cover"

what is a spark plug cover?
the plug wire?

[Jason2tpa]

good to hear it is running well now.
what do you mean by
"the spark plug cover for the No. 1 plug was laying on the bottom of the engine cover"

what is a spark plug cover?
the plug wire?

Yes, since OP stated only 3 of 4 cylinders were firing. The spark plug coil lead cap.

[Merganser]

Yes it was spark plug coil lead cap,

[robert graham]

It sounded like only 3 of 4 cylinders was firing....a plugged injector screen or plug wire loose would do it.....the motors actually run fairly well on 3 cylinders except the loss of RPM's and power....What a simple fix!

[zenoahphobic]

I am glad you persisted on your hunch that something was not quite right and found the problem.
This indicates your dealer did not check the engine after installation, and that he lacks expertise or diagnostic skills, given that he had the boat there in front of him with your description of the problem.

[Merganser]

Yes not at all what I expected. ON the plus side I am more dialed into my outboard and that can only be a good thing