Boston Whaler w/ Dual E150txcc. WOT rpm?

[Challenger84]

I just picked up a 26' Boston Whaler with dual 1988' e150txcc 150hp Evinrudes.
I can get her to go about 33-34 mph on gps with the WOT @ 3900 rpm.
Prop size is 15x17.
My question is it safe to ride that low of an RPM?
What is the recommended WOT RPM range for these types of engines?
What prop do you guys suggest me getting?

I have a few photos I included.
I know how everyone loves pictures!
Thanks guys

 

[Chris1956]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

That is pretty low RPM. You want to be at 4500 minimum. Are you trimmed out?

You would need to drop the pitch 3-4" to gain 600-800RPM at WOT.

 

[Challenger84]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

That is pretty low RPM. You want to be at 4500 minimum. Are you trimmed out?

You would need to drop the pitch 3-4" to gain 600-800RPM at WOT.

That seems to be a major drop in pitch.
(change to 15x13?)
Does the rule still apply when you have dual OB?
Would you think a sick engine might be the cause?
Maybe not running at full potential?

I'll probably need to tune up both the OB and see if that makes a difference. I can't imagine the original owner driving around like that.
I'll get back with updates as I go along.
Thanks for the help.

 

[Chris1956]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

I suppose one engine dould be sick and dragging the other down in RPM. Why not check compression on both and check spark on both and see what you have going.

 

[wilde1j]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

3900 is WAY TOO LOW. Those motors should turn 5800 @ WOT.

 

[Al-53]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

Can you raise one engine as not to drag in the water and run the other to see if it gets WOT alone and then reverse the process..to see if you have one dragging the other down...this way you can see if they are at least performing well...

Al

 

[wilde1j]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

Not likely that boat will plane on one engine. My 23' WA won't plane on one 175.

 

[ezeke]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

That's the fastest the boat can possibly go with the RPM limited to 3900 RPM and 17 pitch propellers.

Clearly, you are lugging the engines. If raising the engines doesn't help you should use a lower pitch propeller. I would just go for the lower pitch now.

 

[Challenger84]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

I'm heading to the boat today and will be preforming a full tune up.
Change the lower lube, plugs/wires, and soak the carbs.
I'll get a compression check on all 12 cylinders to see where I'm at.
I hope that helps get the rpm up a little bit then I will see which exact props will work for me.

Thanks for the advice guys!

 

[keefallan]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

I posted much earlier this morning but it didn't post. I definately think something is amiss. Go the tune-up route and post what you find. My dad had a 26 welcraft coastal with twin 225's and it had at least 26" and maybe 28" props on it! I don't 17's are wrong just yet.
Your boat definately won't get on a plane with one screw by the way(as previously stated)!
I think it is a mechanical issue first. Good luck.

 

[ezeke]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

Whale of a difference between twin 150's and twin 225's.

My point is that it is not mechanically possible to go faster as long as the RPM is limited to 3900 RPM and the pitch is 17 for whatever reason.

 

[keefallan]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

there definately is a whale of a difference between the 2 motors. But there is definately a big difference between 17 and 26 pitches. I just think that it is a fuel limiting issue or something else being missed. I know it sounds crazy...are the tachs accurate? Are the butterflies opening all the way?

However, from a mechanical point of view, I agree with EZEKE. Spin the motors faster with less pitch and see what happens. But, how much smaller can you go with those props? You'd have to go down to a 13" prop? Is there even such a beast? It's not like the application is a one-off situation. There must be many 25-26' boats with twin 150's. What's the average pitch for them?

 

[wilde1j]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

there definately is a whale of a difference between the 2 motors. But there is definately a big difference between 17 and 26 pitches. I just think that it is a fuel limiting issue or something else being missed. I know it sounds crazy...are the tachs accurate? Are the butterflies opening all the way?

However, from a mechanical point of view, I agree with EZEKE. Spin the motors faster with less pitch and see what happens. But, how much smaller can you go with those props? You'd have to go down to a 13" prop? Is there even such a beast? It's not like the application is a one-off situation. There must be many 25-26' boats with twin 150's. What's the average pitch for them?

You'd be looking at a bunch of underpowered boats!

 

[ezeke]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

That's a Guardian hull, probably rated at 600HP with a Minimum HP rating of 300HP. That is one hell of a gunboat when it's rigged correctly.

http://www.brunswickcgp.com/boat/27-guardian/

 

[Challenger84]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

The Whaler is rated at 450 hp max with a 12 person max.
I went to visit the boat to day and spent over $1000 on parts alone.
Double the pleasure dbl the fun and cost!
I got the port side engine running like a top.
I bearly turn the key and it started right away.
The other engine on the other hand when I took things apart I noticed the wiring was all scuffed up.
I ordered 12 new coils and 4 ing. packs.
I did a spark test and the spark was VERY weak.
I'm just waiting on the parts to come in now and hopefully when I change them out it will fix the problem.
I'll keep everyone updated as I find anything new.
I didn't get to test the "good" engine out in the water but it sounds WAY healthier then before.

Thanks everyone for the help and advice!

 

[Challenger84]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

That's a Guardian hull, probably rated at 600HP with a Minimum HP rating of 300HP. That is one hell of a gunboat when it's rigged correctly.

http://www.brunswickcgp.com/boat/27-guardian/

I was doing some research and it appears to be a "Temptation" Model
70% of 450 would be 315hp so I am a little underpowered.
I plan on running it for awhile and then upgrade to two 225hp OB's or I might just sell it and upgrade to a bigger boat with enough power.
We'll see how it preforms when the OB's I have are in tip top shape.
Thanks again everyone.

 

[ezeke]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

Here's a link for some discussion on the Temptation power options: http://continuouswave.com/ubb/Forum4/HTML/006701.html

 

[Challenger84]

Re: Boston Whaler w/ Dual E150txcc. WOT rpm?

^thanks fr the link!
Some very interesting info.