18 Footer Engine Prop Issues.-

[Sea Rider]

This is a prime example about the importance of dialing best engine/transom height to optimize combo's performance under all water cond. Do you find this engine set-up correct, will combo achieve, good, excellent, lousy water performance if tested on water? see any flaws, inconsistencies somewhere ?



Everybody talks about prop slip, rpm, pitches, best hole shot, etc. All that data comes into play nicely afterwords best engine/transom height is dialed. Best propulsion = Best performance.

Scenario :
2 stroke Merc 150 HP powering a Four Winns 18 footer for OB use. Don't ask about wot rpm, hole shot, top speed, overall performance, this combo is under dry evaluation right where combo is parked. This combo was rigged by a local "20 year expert boat/engine dealer"

Happy Boating

 

[Frank Acampora]

Well, you would think that the hull manufacturer would have done on water testing to verify approximate engine height. Your dealer simply hung the engine on the transom as evidenced by the clamps resting on the top. The hull has a built in set back and the engine is about two feet back from the actual transom Such a large set back requires the engine to be set higher BUT----As I said before you would think the manufacturer would have tested the design. SO: Test the boat as it is and if it requires more lift then raise the engine. OR: Write the manufacturer (if still in business) and ask their opinion.

 

[Frank Acampora]

I don't pay much attention to 20 year experts. They may have been making the same "misteakes" for 20years. It appears that the dealer has simply hung the engine directly on the mounting box as evidenced by the mounting clamps sitting directly on top. Your engine actually sits about two feet back from the end of the actual transom. this requires more engine height. However, you would think that the hull manufacturer would have water tested the design and tuned the mounting box to the approximate correct height. SO: Either write the manufacturer (if still in business) and ask, or run the boat and see what it needs. Try the Four Winns owners forum. You may get some good feedback there.

 

[b.gagnon]

An 18' boat with a 150hp outboard (Proper running) that needs a hydrafoil could not possibly be set up right! Without getting RPM's you will never know!

 

[Sea Rider]

Some tech facts :

-Manufactures don't care which engine will be used, all engines although being SML could vary its lenght a bit at lower tail.
-OB manufacturers don't care which boat you'll be powering it with. They just manufacture lots of OB's.
-Taching rpm while at the hole shot is useless at all if having a very difficult to plane combo.
-Wot rpm at full throttle is critical, that's other story that can be optimized by maximizing the prop afterwords if needed.

Frank, you're right huge years of alleged expertise or experience doesn't mean a thing as this example will prove.

To resume the post : Which water performance : good, excellent, lousy should that combo achieve and why once is placed on water while having load well distributed on deck, well trimmed and riding on near flat water straight water courses. Just want to see how you guys address engine installations.

Happy Boating

 

[Sea Rider]

Hint, check marked red line on previous pic , will that tell you something....? How about lower yellow line with respect to hull ?

Happy Boating

 

[Sea Rider]

As no one will answer this post providing a proper answer of their knowledge or rigging skills, here is what was found during the dry evaluation and final wot test by owner.



-Red line indicates engine sits way too deep on water while moored or just floating bare bone, check all the paint deterioration at engine's side bracket.

-Green line, that's where water level should be around when floating if engine sits at a proper height.

-Yellow line, distance from lower set back to AV plate, which doesn't say a thing, at least to me.

General Mismatches :

Engine :
-This engine seems to be be a 2 strokes XL shaft when that combo needs a L shaft engine.
-Dealer has installed a XL left over instead of a L version.
-Has already raised engine on transom near 2" to his knowledge in order to "solve the leg size issue" and voil?.
-Engine has about 2 more bracket holes to raise and that will be all folks.
-Engine's lower pan rests near even at water level.

Transom :
This model has a aft built in set back of just 40 cm height, the one who designed that model is plain crazy, you can sit on that transom height a S shaft engine of same HP and work much better. That boat has a middle cut transom, would have been much better to make it straight even as per both sides and have engine sitting at a much friendly higher level to play with.
-Owner will need to modify transom height, install an engine mount, engine raisers, jacks are not available down here. But as long that combo suits his wakebording needs will be ok for him. What he doesn't know is all about the huge lugging his engine is experiencing while wakeboarding while heavily passenger loaded...

Water performance :
Will leave that one to anybody willing to comment now that you have all the tech issues found : will combo perform good, so-so, crappy ?

Side note : When will Iboats reinstall again the edit button on a permanent basis, the edition is awful, lots of typo errors which were not originally written appears on text, unfriendly window display " SERVER RESPONSE, PLEASE TRY AGAIN, AGAIN AND AGAIN peeping out on a regular basis which turns me completely nuts and talkig on behalf of other posters as well.

Happy Boating

 

[Sea Rider]

Find that boat model to sit and ride quite deep on water, assume due to its near 1 ton bare bone weight with engine, Once on its way the scenario changes just a bit from previous dead stop seated.

The test proved......



Awful and real crappy performance, the pic was shot at fast plane, huge amount of water blowing up backwards, worsens when giving juice to engine, wakeboarder will benefit refreshing himself there if being close to engine. Imagine the excesive middle and lower leg drag being produced there. It's a cocktail of improper engine height, excesive lower leg drag, engine lug, poor performance and passenger fun.

Before launching combo into the water, knew this was going to happen just by watching the "out of this world spot-on dry delaer installation"...

Happy Boating

 

[Sea Rider]

I sometimes wonder the great capacity to determine if a combo has a spot on height seated engine and its performance by having a look while passing by at speed on near flat water cond.



This is another prime example of owner boating with a combo that to his fully content performs satisfactorily to him just by seating engine on transom and voil?. As a boating rehearsal can you determine what's going on at back transom and why ?

Happy Boating

 

[Sea Rider]

Just for the record....

- Bow passenger & load should be way up front for combo to ride parallel to water level at plane,

- Using a long shaft OB when his transom is a short one.

- Water flow hits round portion at lower leg, splashes against back transom diverting splash backwards, worsens as speed increases.

- This cond creates a high middle wake, when that should be flat even if engine is correctly height transom seated.

The remedy : Install an engine mount or a second "water deflector plate" on lower leg where splash is being produced and voil?...

Happy Boating