Should my boat be faster?

[patrickj]

Ive got a 17 foot cajun bassboat with a85 horse force outboard. Im trying to figure out why it seems so slow to me... At wide open throttle trimmed up in calm water i get about 23 miles an hour at 5400 rpm... seems to me like it should go about 10-15 miles an hour faster... am i confused?

 

[buckage]

Re: Should my boat be faster?

How heavy is the boat....if it is waterlogged....an 85 could struggle....cold be miss propped, how is the hull, any "hooks" in the glass?

Is the anchor in the boat? Yes, if dry, it should do around 35-40 with the right prop (no spun hub), no extra weight etc.

 

[patrickj]

Re: Should my boat be faster?

supposedly the boat weighs 600 something pounds, im sure it is miss prop'd the prop seems a little large to me it has a 21 pitch prop... which seems a little too big. As for water logged, it definitly has water in the foam... im crossing that bridge now...it had about a pound of water in a 6 inch cube of foam... ive been drying it out for about a week with floor dryers and heaters and fans and im down to about .3 pounds for a 6 inch cube of foam... i think at most it has about 60-80 pounds of water in it right now and im still drying it out even further. there is no anchor . When im doing my speed test ive got 4 batteries 18 gallons of gas 2 adults fishing gear ice chest... im thinking i should be running about 35 miles an hour.

do you think it being over prop'd could cause that much of a reduction in speed

 

[The Rooster]

Re: Should my boat be faster?

Yes, somethings not right, Patrick. Thats an aluminum rig correct? Shouldn't be a waterlogged issue. Spun bushing in the hub, maybe. Is that a GPS speed and does it really seem that slow ? RPM's, if correct, seem OK. Is this your first time w/ this rig ?

 

[roscoe]

Re: Should my boat be faster?

If you were overpropped, your rpm would drop significantly.

I'd bet you have a lot more water in the foam, stringers, and transom, than you think.

Your hull has to weigh more than 600.
A 17' aluminum weighs 750-1000 depending on setup.
Yours is likely 1100 +.
Add motor, fuel, batteries. gear, trolling motor, guys, == now you are pushing 2100#

Add 200# of water to an already burdened boat, and it is just too heavy.

What is the model and year of this boat?


And good luck getting the water out with blowers and heaters.

 

[patrickj]

Re: Should my boat be faster?

its a fiberglass boat, thats a gps speed and i have a new lowrance and it has a speed sensor and it says the same thing... i ran it right next to my buddys boat and he said i was going 25. ive had this boat for about a year. been out in it many times just recently realized that its not very fast compared to other boats of it size.

 

[patrickj]

Re: Should my boat be faster?

I'd bet you have a lot more water in the foam, stringers, and transom, than you think.

Your hull has to weigh more than 600.
A 17' aluminum weighs 750-1000 depending on setup.
Yours is likely 1100 +
Add motor, fuel, batteries. gear, trolling motor, guys, == now you are pushing 2100#

and good luck getting the water out with blowers and heaters.

Ive already gotten a ton of water out of it, think ill keep going and see how much more i can get out. i read on a website some where that it weighed like 685 for just the hull, but ive been wrong before. ill take it to a scrap scale and get it weighed this weekend.

My thing is that the boat sits up out of the water at full speed just like it should, its planning out good, it rides good, doesnt sit low in the water, doesnt take on water... i think the motor is puttin out the power it just isnt making it to the water. i guess im going to take the prop and have it looked at. The boat is a cajun espirit encore thats about all i know about it. i picked it up cheap and i take it fishing... alot. i dont really need it to go any faster but if its there id like to use it. i dont think the water logged foam is the problem, im pretty sure its minimal now... the foam was never wet until we had some storms and it blew my tarp off and rain water got in and the drain was plugged. and this was in the last couple weeks... im going to keep blowing the foam dry for a few more weeks and recheck it periodicly.

 

[roscoe]

Re: Should my boat be faster?

I realize it is a fiberglass boat, and it will be a lot heavier than an aluminum boat, thats why your estimate of 600# seems way off to me.

What is the model and year of this boat? That way I can look it up and give you the exact hull weight.

 

[patrickj]

Re: Should my boat be faster?

and the boat is fiberglass not aluminum... seems to be some mass confusion about that


Its a 1988 cajun encore espirit

the hull weights 750 pounds according to this website... its a 1988 cajun by mastercraft

 

[roscoe]

Re: Should my boat be faster?

No confusion about the glass boat.
Just comparing several known aluminum boats in the same size and hp range, and knowing that the glass boats are heavier than tin ones.

That motor should push a 1300-1400# rig at 40+ mph.

Don't see an encore model listed in NADA , iboats,
17' 88 cajun esprit combo 750#
17' 88 cajun esprit sport 1160#
17' 88 cajun esprit Entrepreneur 1200#

I see a 1986 model encore esprit listed, at 900#

These boats are rated for 125-175 hp, depending on model, so there is part of the answer.

 

[lesbrou]

Re: Should my boat be faster?

In 1988 Cajun had a 16.5" boat dry at 750lb , max hp 125 & a 17.5" boat dry at 1100lb , max hp 150 . I think your under hp .

 

[patrickj]

Re: Should my boat be faster?

I have the Cajun espirit combo 16.5 foot max motor 125...

The boat came factory with a 90 horse... There's a guy at the camp ground I go to he has the same boat but it's a 1989 with a 90 horse Johnson... It'll run 40+ loaded with all the gear... I agree the motor seems a touch small but 23 miles and hour don't seem right... I took the prop off early this morning... Something don't look right with it... I'm headed to the prop shop this morning... I'll post when I find out more.

 

[metriccrescentwrench]

Re: Should my boat be faster?

I don't know what the max rpm spec is for your engine, but 5400 seems low, and that 21 pitch prop seems like too much. You want to choose your prop pitch so you're running near the top end of the max rpm range. When I was getting my Checkmate setup after rebuilding it I could only get about 5400 rpms and 54 mph with a 25 pitch prop, and it was a dog getting up to speed. I went to a 23 pitch prop and jumped up to 6000 rpms and 62 or 63 mph (with a little bit more to be gained through fine tuning jackplate height). The change won't be as pronounced in your case, but you're definitely hurting performance with too much prop.

As far as wet foam, you're never going to get all the water out of it. Also, if the foam is that wet you've more than likely got other issues as well (rotting stringers, deck, and transom). I don't mean to rain on your parade, but I've been-there-done-that two times now.

 

[Philster]

Re: Should my boat be faster?

(Boat is wet) + (motor is weak/worn) + (someone underpropped it to compensate) = slow

 

[bonzoscott]

Re: Should my boat be faster?

85 hp + 23mph + 5400 rpm = spun prop

 

[ezmobee]

Re: Should my boat be faster?

You should be able to see 35 with that setup but not higher than that in my opinion. You've got to be heavy, badly propped, or maybe even dropping a cylinder. Outboards can run and sound normal with a dead cylinder but lack power.

 

[roscoe]

Re: Should my boat be faster?

He's running an 85 hp Force, 5400 is the top end of recommended rpm range.

Has anyone here really ever experienced a spun prop that lasted for a year, and only revved to 5400, and still pushed the boat 23 mph ?

I was thinking dropped cylinder too, but don't know if he would hit 5400 rpm .

 

[ezmobee]

Re: Should my boat be faster?

I had a spun prop that would only slip when you floored it. Still, probably not the issue here.

 

[Philster]

Re: Should my boat be faster?

The problems are likely two:

1)Heavy/wet boat.
2)Weak engine.

These are two common problems on older boats. What has been said about the boat, and knowing the Force, these are not wild guesses here; rather, they are likely conclusions.

That's it. Why can it redline? The prop pitch has been dropped to compensate.

This is common. Barring additional information, it's the simplest explanation.

Occam's razor: http://en.wikipedia.org/wiki/Occam's_razor

Might as well get all smart and stuff during the off season.

 

[patrickj]

Re: Should my boat be faster?

ok jason from the prop shop called about 20 minutes ago, he said the rubber bushing inside the prop is bad worn, and it slips under heavy load, he also said my prop was in terrible shape and one of the 3 blades was even bent off true, he thinks the prop is slipping at wide open throttle and he thinks the prop needs to be true'd. Ive always had quite a bit of vibration at mid range rpms. i would assume the bent blade is why. I do alot of shallow water trolling with the motor... i only paid 300 dollars for the boat just so we can use it to run jugs in the back waters so it takes a beating. Its going to cost me about 110 dollars but ill have the prob back tomorrow and ill take it out and test it this weekend. i appreciate everyones input and i will test the boat as soon as i get the prop back on tomorrow afternoon and ill let you know. but he seems to think this will solve all my problems.


He also pointed out that the high end of my rpm range is 5200 rpm which is what the tag on the leg of the motor says(ive never seen that until he asked me to look for it) and with such a large prop he doesnt think it should be spinning at 5400 and that is caused by the rubber bushing... he thinks with the new bushing ill tach out at about 4600-4800.